Transition milk or milk replacer powder as waste milk supplements to cold-stressed neonatal Holstein dairy calves: Effects on performance, feeding behavior, and health

Young calves are more susceptible to cold than older animals due to their limited ability to regulate body temperature and lack of fat reserves and may have difficulty consuming the energy needed to cope with the cold by maintaining body temperature and meeting their metabolic needs, especially when fed constant levels of waste milk (WM) with less solids, which can be detrimental to health and future performance. An alternative to overcome this problem is increasing the milk's solids content to the existing volume by using different sources [milk replacer powder (MR) or transition milk (TM)]. Thus, we aimed to evaluate the effects of increasing the total solids of WM via MR (WM+MR) or TM (WM+TM) on the performance, feeding behavior, and health-related variables of cold-stressed dairy calves during pre- and post-weaning. We hypothesized that feeding WM supplemented with MR or TM as potential liquid feed enhancers would improve milk dry matter and energy intake of the calves with a positive impact on body development and have no negative impact on feeding behavior and health. Additionally, we hypothesized that MR would not differ from TM. As a sample size calculation at 80% power using power analysis (PROC POWER) in SAS 9.4, a total of 51 Holstein-Friesian vigorous male calves [vigor score 21-27; 17 per treatment; 4-d old; body weight (BW) = 40.0 ± 0.63 kg (mean ± SD)] were selected, assigned randomly to treatments, and housed in individual pens in an outdoor barn. Irrespective of the type of treatment, all calves were fed 6 kg/d liquid feed from d 1 to d 53 of the experiment. In a step-down weaning program, calves received 0.5 kg liquid feed from d 54 to d 60. All calves were weaned on d 61 and remained in the study until d 101 as post-weaning evaluation. The calves had ad libitum access to starter feed and fresh drinking water across the experiment. Intake, growth, and behavior data were analyzed using a general linear mixed model and health data were analyzed using mixed logistic regression, mixed linear regression, and survival analysis models in SAS. We found that supplementation was responsible for a greater dry matter intake (DMI; P = 0.004), superior average BW (P = 0.037), and increased crude protein (CP; P = 0.001) and crude fat (CF; P = 0.001) intakes, with the most favorable outcomes observed for the WM+TM group when compared with WM+MR. Animals fed WM (control group; CON) showed a smaller average daily gain during the first 40-d of life (P = 0.026), showing slight changes during the whole period of evaluation when compared with the supplemented groups (SUP; WM+MR and WM+TM). No difference between MR- and TM-SUP groups, probability of having abnormal appearance (P = 0.032) and pneumonia occurrence (P = 0.022) was reduced in the SUP than in CON animals, with no effect on diarrhea among treatment groups (P = 0.461). Using milk supplements added to WM is an alternative to improve the intake, performance, and health of young calves under cold stress. Our findings showed that SUP animals outperformed the CON group in terms of DMI, average BW, and intake of CP and CF, with the TM-SUP group displaying the most favorable outcomes. Moreover, the SUP groups demonstrated reduced odds of experiencing abnormal appearance and pneumonia, highlighting the positive impact of supplementation on calf health.

Subcutaneous lysophosphatidylcholine administration promotes a febrile and immune response in Holstein heifer calves

Lysophosphatidylcholine (LPC) is immunomodulatory in nonruminants; however, the actions of LPC on immunity in cattle are undefined. Our objective was to study the effects of LPC administration on measures of immunity, liver health, and growth in calves. Healthy Holstein heifer calves (n = 46; age 7 ± 3 d) were randomly assigned to 1 of 4 treatments (n = 10 to 11 calves/treatment): a milk replacer diet unsupplemented with lecithin in the absence (CON) or presence of subcutaneously (s.c.) administered mixed (mLPC; 69% LPC-16:0, 25% LPC-18:0, 6% other) or pure LPC (pLPC; 99% LPC-18:0), or a milk replacer diet supplemented with 3% lecithin enriched in lysophospholipids containing LPC in the absence of s.c.-administered LPC (LYSO) for 5 wk. Calves received 5 s.c. injections of vehicle (10 mL of phosphate-buffered saline containing 20 mg of bovine serum albumin/mL; CON and LYSO) or vehicle containing mLPC or pLPC to provide 10 mg of total LPC per kilogram of BW per injection every 12 h during wk 2 of life. Calves were fed a milk replacer containing 27% crude protein and 24% fat at 1.75% of BW per day (dry matter basis) until wk 6 of life (start of weaning). Starter grain and water were provided ad libitum. Body measurements were recorded weekly, and clinical observations were recorded daily. Blood samples were collected weekly before morning feeding and at 0, 5, and 10 h, relative to the final s.c. injection of vehicle or LPC. Data were analyzed using a mixed model, with repeated measures including fixed effects of treatment, time, and their interaction. Dunnett's test was used to compare treatments to CON. Peak rectal temperatures were higher in mLPC or pLPC, relative to CON. Plasma LPC concentrations were greater in mLPC and LYSO calves 5 h and 10 h after the final injection, relative to CON. Calves receiving mLPC and pLPC also had higher circulating serum amyloid A concentrations, relative to CON. Calves receiving mLPC had greater serum aspartate aminotransferase, γ-glutamyltransferase, and glutamate dehydrogenase concentrations, relative to CON. Calves provided mLPC experienced lower average daily gain (ADG) after weaning, relative to CON. The LYSO treatment did not modify rectal temperatures, ADG, or measures of liver health, relative to CON. We conclude that LPC administered as s.c. injections induced an acute febrile response, modified measures of liver and immune function, and impaired growth in calves.

Is Personal Protective Equipment Worth the Hassle? Annual Risk of Cryptosporidiosis to Dairy Farmers and How Personal Protective Equipment and Handwashing Can Mitigate It

Cows are known carriers of Cryptosporidium parvum (C. parvum), a protozoa that can cause the gastrointestinal illness cryptosporidiosis in humans. Despite this potential exposure, dairy farmers tend to wear personal protective equipment (PPE) to protect the milk from contamination, rather than to protect themselves from zoonotic diseases, such as cryptosporidiosis. In this study, cow feces were collected from individual cattle on dairy farms and analyzed for C. parvum using qPCR. Quantitative microbial risk assessment (QMRA) was used to determine the risk of cryptosporidiosis to the dairy farmer with and without the use of handwashing and PPE (gloves and masks). The annualized risk of cryptosporidiosis to dairy farmers was 29.08% but was reduced significantly in each of the three interventions. Among the individual interventions, glove use provided the greatest reduction in risk, bringing the annual risk of cryptosporidiosis to 4.82%. Implementing regular handwashing, the use of gloves and a mask brought the annual risk of cryptosporidiosis to 1.29%. This study provides evidence that handwashing and PPE use can significantly reduce the risk of cryptosporidiosis to farmers and is worth implementing despite potential barriers such as discomfort and cost.

Graduate Student Literature Review: Reducing mortality and morbidity in transported preweaning dairy calves: Colostrum management and pretransport nonsteroidal anti-inflammatory drug administration

Currently, mortality and morbidity rates for preweaning calves in the US dairy industry are high, with the major cause being digestive disorders and respiratory diseases. One of the most important management practices that can reduce calf mortalities and morbidities is the feeding of colostrum, provided its quantity, quality, and cleanliness, and timing of feeding are according to recommendations. However, other management practices similar to transportation, can also compromise calf health and production performance. When preweaning calves are transported, stressors similar to physical restraint, commingling, dehydration, bruising, and pain may lead to an inflammatory response and immunosuppression, which has been seen in older cattle, and could increase susceptibility to digestive disorders and respiratory diseases. One strategy that could potentially reduce transport-related negative outcomes is the pretransport administration of nonsteroidal anti-inflammatory drugs, such as meloxicam. This review provides a brief background on preweaning mortality and morbidity, colostrum management, transport-related stress, use of nonsteroidal anti-inflammatory drugs in transported calves, and highlights some of the current knowledge gaps.

Effects of Echinacea purpurea supplementation on markers of immunity, health, intake, and growth of dairy calves

Echinacea purpurea (EP) is an herb that has demonstrated immunostimulatory and anti-inflammatory effects with the potential to improve immunity, health, and performance in animals. The objective of this study was to investigate how supplementing calves with EP affects their blood immunity marker profile, health, intake, and growth. Male Holstein calves (n = 240), sourced from local dairy farms or auction, arrived at a rearing facility between 5 and 14 d of age and were kept in individual pens in 1 of 3 rooms (80/room) for 56 d, and then put into groups for the remaining 21 d of the trial. Calves received milk replacer (MR) 2× per day for 56 d (total = 36 kg of MR) and had ab libitum water and starter access. Within room, calves were randomly assigned to 1 of 3 treatments: (1) control (n = 80), (2) 3g of dried (powder) EP extract per day split over 2 milk feedings from experiment d 14-28 (n = 80), and (3) 3 g of dried (powder) EP extract per day split over 2 milk feedings from experiment d 1-56 (E56; n = 80). The powdered EP treatments were mixed into the liquid MR. On d 1, 14, 28, and 57 rectal temperatures and blood were collected from a subset of calves (n = 117; 39 calves/treatment), and blood serum was assessed for serum total protein (d 1), haptoglobin, white blood cells, and cytokines. Failed transfer of passive immunity was defined as serum total protein <5.2 g/dL. Calves were health scored 2× per day, receiving fecal and respiratory scores until d 28 and 77, respectively. Calves were weighed on arrival and then weekly until d 77. Milk replacer and feed refusals were recorded. Supplementation of EP was associated with lower haptoglobin levels, segmented neutrophil counts, segmented neutrophil per lymphocyte ratio, respiratory scores in auction derived calves, and higher lymphocyte counts and d 28 rectal temperature. Of calves with heavier arrival body weight, E56 calves had greater postweaning weekly body weight. There was no detected effect of EP supplementation on total white blood cells, band neutrophil, monocyte, and basophil counts, IL-10, IL-6, and TNF-α levels, fecal scores, risk of receiving diarrhea and respiratory treatment, risk of bovine respiratory disease (calves were deemed at risk for bovine respiratory disease if they had at least 1 respiratory score ≥5), risk of mortality, MR and feed intake, average daily gain, and feed conversion ratio. Overall, EP supplementation to dairy calves was associated with immunomodulation and reduced inflammation, evidenced through blood markers, although only few minor health and growth improvements were observed. Benefits were observed particularly when fed across the whole milk feeding period.

A randomized controlled trial investigating the effect of transport duration and age at transport on surplus dairy calves: Part I. Impact on health and growth

Calves arriving to veal and dairy-beef facilities in poor condition are at risk of future health challenges and reduced growth rates, and limited knowledge is available on how time in transit affects subsequent health and growth of these animals. The objective of this randomized controlled trial was to understand the effects of transport duration on diarrhea, respiratory disease, and growth of surplus calves destined for veal production following 6, 12, or 16 h of continuous road transport. Surplus dairy calves (n = 175; 7 transport cohorts) from 5 commercial dairy farms in Ontario, Canada, were enrolled on the day of birth. These calves were clinically examined daily on the source farms until the day before transport and on a daily basis for the first 14 d at the veal farm. On the day of transport, they were randomly assigned to 6, 12, or 16 h of transport to a veal farm. A blood sample was collected between 24 and 48 h of birth to assess transfer of passive immunity status. Calves were weighed at birth, before and immediately after transport, as well as 24, 48, and 72 h after unloading. Calves were also weighed 14 and 50 d after transport. Health exams were conducted daily at the source farm, immediately before and after transport, and once daily for 14 d thereafter to evaluate clinical signs of diarrhea, respiratory disease, dehydration, and navel inflammation. Mixed effects Poisson regression models were used to evaluate variables associated with the number of days with abnormal respiratory and fecal scores, whereas mixed logistic regression models with repeated measures were built to assess the probability of a calf having abnormal respiratory scores, abnormal fecal scores, or dehydration by day after arrival to the facility. A mixed model with repeated measures was used to evaluate calf weight at each time point at which body weight was measured after transport, whereas a mixed linear regression model was used to evaluate factors associated with average daily gain (ADG) in the 50 d after transport. Calves transported for 16 h had greater incidence of abnormal fecal scores compared with 6 h in the 14 d after transport. In addition, an interaction between age and duration of transport on the number of days with abnormal respiratory scores was identified, where calves older than 7 d of age had reduced incidence of abnormal respiratory score compared with calves 2 to 6 d old, even when transported for 16 h. As for growth, age at transport was positively associated with ADG in the 50 d of observation; however, no differences were observed between transport duration groups. These findings highlight that transporting calves for a longer duration negatively affects subsequent health, and calves greater than 1 wk of age experience improved health and growth after transport compared with their younger counterparts.

Welfare of calves

This Scientific Opinion addresses a European Commission request on the welfare of calves as part of the Farm to Fork strategy. EFSA was asked to provide a description of common husbandry systems and related welfare consequences, as well as measures to prevent or mitigate the hazards leading to them. In addition, recommendations on three specific issues were requested: welfare of calves reared for white veal (space, group housing, requirements of iron and fibre); risk of limited cow–calf contact; and animal‐based measures (ABMs) to monitor on‐farm welfare in slaughterhouses. The methodology developed by EFSA to address similar requests was followed. Fifteen highly relevant welfare consequences were identified, with respiratory disorders, inability to perform exploratory or foraging behaviour, gastroenteric disorders and group stress being the most frequent across husbandry systems. Recommendations to improve the welfare of calves include increasing space allowance, keeping calves in stable groups from an early age, ensuring good colostrum management and increasing the amounts of milk fed to dairy calves. In addition, calves should be provided with deformable lying surfaces, water via an open surface and long‐cut roughage in racks. Regarding specific recommendations for veal systems, calves should be kept in small groups (2–7 animals) within the first week of life, provided with ~ 20 m²/calf and fed on average 1 kg neutral detergent fibre (NDF) per day, preferably using long‐cut hay. Recommendations on cow–calf contact include keeping the calf with the dam for a minimum of 1 day post‐partum. Longer contact should progressively be implemented, but research is needed to guide this implementation in practice. The ABMs body condition, carcass condemnations, abomasal lesions, lung lesions, carcass colour and bursa swelling may be collected in slaughterhouses to monitor on‐farm welfare but should be complemented with behavioural ABMs collected on farm.

Effects of feeding Saccharomyces cerevisiae fermentation products on the health and growth performance of Holstein dairy calves

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Feeding dairy calves SCFP in milk replacer and solid feeds until 4 mo improved postweaning ADG and feed efficiency.

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SCFP reduced respiratory illness antibiotic treatments in calves.

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Feeding SCFP to calves did not affect daily fecal scores or preweaning growth.

It is essential to reduce antibiotic use in the livestock industry, which leads to a need for alternatives to antibiotics that reduce illness and promote growth in dairy calves. The objective of this study was to evaluate the effect of feeding dairy calves Saccharomyces cerevisiae fermentation products (SCFP) on average daily gain (ADG) and antibiotic use in dairy calves through 4 mo of age. Holstein bull calves (n = 60; 5 ± 3 d old) were blocked by body weight (BW) and serum total protein (STP) and assigned to 1 of 2 treatments. The control treatment (CON) fed a 24% crude protein (CP):17% fat milk replacer (MR), calf starter, grower #1, and grower #2 with no SCFP added. The SCFP treatment fed the same MR with 1 g/d of SCFP, calf starter with 0.8% (dry matter; DM) SCFP, grower #1 with 0.44% (DM) SCFP, and grower #2 with 0.275% (DM) SCFP. Calves were offered 2.84 L (12.5% solids) of MR twice daily (0630 and 1630 h) through d 51 and MR once daily (0630 h) from d 52 to 56, and were weaned on d 57. From d 1 to 56, calves also received ad libitum access to calf starter and water. On d 57, calves were switched to grower #1 and on d 84, calves were switched to grower #2, which contained a lower level of CP and a higher level of neutral detergent fiber (NDF). Individual calf BW, body condition score (BCS), hip height (HH), and hip width (HW) were measured biweekly from d 0 to 112. Feed intake was recorded daily, and feed efficiency (gain:feed) and ADG were calculated. Daily fecal and respiratory scores were recorded for each calf through d 56, and all medical interventions were recorded for the duration of the study and grouped based on illness. We found no effect of treatment on STP, BW, BCS, HH, or HW at d 0 or 56, nor effects on preweaning ADG and feed efficiency. No treatment effect was observed for BCS or HH at d 112; however, BW and HW were increased in SCFP calves at d 112. A treatment tendency was observed for postweaning ADG, with SCFP calves being larger than CON calves and SCFP calves having improved feed efficiency compared with CON calves after weaning. A treatment effect was observed for respiratory treatments postweaning, with SCFP calves being treated less frequently than CON calves. Our results suggest that feeding SCFP to calves improves postweaning growth and feed efficiency, and reduces postweaning respiratory disease interventions.

Invited Review: Antimicrobial Use and Antimicrobial Resistance in Pathogens Associated with Diarrhea and Pneumonia in Dairy Calves

Antimicrobial use (AMU) is the major driver of antimicrobial resistance (AMR) among bacteria in dairy herds. There have been numerous studies on AMU and AMR in dairy cows; however, studies on AMU and AMR in dairy calves are limited. A comprehensive overview of the current state of knowledge of AMU and AMR among pathogens in dairy calves is important for the development of scientifically supported and applicable measures to curb antimicrobial use and the increasing risk of AMR. Therefore, we performed a systematic review of research on AMU and AMR in dairy calves. A total of 75 publications were included, of which 19 studies reported AMU data for dairy calves and 68 described AMR profiles of the four most prevalent bacteria that are associated with calf diarrhea and calf pneumonia. Large variation in AMU was found among herds across different regions. There seems to be a positive association between exposure to antimicrobials and occurrence of resistance. Most AMU was accounted for by treatment of diseases, while a small proportion of AMU was prophylactic. AMU was more common in treating calf diarrhea than in treating pneumonia, and the resistance rates in bacteria associated with diarrhea were higher than those in pathogens related to pneumonia. Organic farms used significantly fewer antimicrobials to treat calf disease; however, the antimicrobial resistance rates of bacteria associated with calf diarrhea and pneumonia on both types of farms were comparable. Feeding waste or pasteurized milk was associated with a higher risk of AMR in pathogens. Altogether, this review summarizes AMU and AMR data for dairy calves and suggests areas for future research, providing evidence for the design of antimicrobial use stewardship programs in dairy calf farming.

Preparing Male Dairy Calves for the Veal and Dairy Beef Industry

Surplus male dairy calves experience significant health challenges after arrival at the veal and dairy beef facilities. To curb these challenges, the engagement of multiple stakeholders is needed starting with improved care on some dairy farms and better management of transportation. Differing management strategies are also needed if calves arrive at veal and dairy beef facilities under poor condition.

Overview of common practices in calf raising facilities

In this literature review, we overview some of the common management practices associated with calf rearing in specialized operations of the United States. Given the growing importance of dairy-beef calves entering the beef production of the United States, we overview aspects related to housing, nutrition, and health events during the pre- and post-weaning period. Based on data on dairy animals, we hypothesize how early life experiences could impact the feedlot performances of dairy-beef animals. Most of the large calf raising operations, where the majority of dairy-beef animals are raised, are located in the Central Great Plains and West regions of the United States. Approximately 80% of calves are individually housed, but the type of housing (e.g., outside hutch, inside a barn) varies based on location of calf-raising facilities. Milk-replacer is fed in more than 80% of operations, while milk (saleable or nonsaleable) is fed in approximately 30% of calf raising facilities (some operations fed more than one type of liquid diet). In addition to liquid feed, water and calf starter are offered ad libitum to calves. Adequate starter intake at weaning is crucial for feed transition from pre- to post-weaning period, which occurs at approximately 2 months of age. Then, calves are mainly housed in group pens and transition from calf-starter to total mixed ration (TMR). Health challenges such as scours and bovine respiratory disease (BRD) can hinder the performance of calves and are major causes of morbidity and mortality in calf ranches. Transportation at a very young age and comingling with animals from other dairies can increase the risk of diseases. Current research efforts are focusing on determining individual factors such as body weight (BW) at arrival or biomarkers of inflammation and stress that can be predictive of disease morbidity, mortality, and performance of calves. Future research should focus on how to utilize this information to optimize management and to develop targeted preventative strategies to reduce incidence of diseases and mortality and improve performance during the pre-weaned period. Also, more research is needed to understand how colostrum management, housing, and nutrition can impact the adult performance of dairy-beef animals.

The Effect of Contract-Rearing on the Health Status of Replacement Dairy Heifers

The aim of this study was to compare the health status of contract- vs. conventionally reared replacement dairy heifers over a 2-year period. A total of 120 dairy farmers were enrolled in the study in spring 2018: 55 farmers were rearing their own heifers (control farmers; CFs), and 65 were sending heifers to a contract-rearing farm (source dairy farmers; SDFs). Between spring 2018 and autumn 2019, approximately 5500 replacement heifers from these farms were monitored for signs of ill health during four farm visits using a modified version of the Wisconsin calf health scoring system. Additionally, faecal and nasal swabs were taken from a proportion of heifers with clinical signs of diarrhoea and respiratory disease to determine the associated aetiological agents. Results indicate few differences in the health status and pathogen exposure status of home-reared versus contract-reared heifers. Additionally, the number of source dairy farms represented and commingling of heifers from multiple origins at the rearing unit were not associated with an increased incidence of respiratory disease or diarrhoea among contract-reared heifers. It was concluded that contract-rearing did not result in adverse health outcomes for replacement dairy heifers. This is the first study to demonstrate this finding in a robust, longitudinal, herd-level population study.

Use of ATP luminometry to assess the cleanliness of equipment used to collect and feed colostrum on dairy farms

The objective of this observational cross-sectional study was to describe the cleanliness of various equipment used for colostrum harvest and calf feeding procedures on dairy farms in Québec, Canada. The study was performed on 42 commercial dairy herds also enrolled in another study aiming to determine the transfer of passive immunity over a 14-mo period. Information on colostrum quality (using Brix value) and cleanliness (total aerobic and total coliform count) were recorded as well as various practices focused on colostrum-feeding equipment and preweaning period using a standard questionnaire. During the study period, colostrum and milk-feeding equipment cleanliness was assessed using direct surface swabbing with Hygiena Ultrasnap swabs. A total of 155 swab samples were obtained from 6 pieces of equipment. Adenosine triphosphate collected from the swabbed surface reacts with the luciferase solution present in the swab by bioluminescence, which is proportional to the quantity of ATP present and quantified as relative light units (RLU). The description of feed equipment cleanliness (defined as the maximal RLU found for a specific herd, dichotomized as <1,000 RLU vs. ≥1,000 RLU) was compared with the herds' descriptive characteristics, focusing on the first 2 components of a multiple correspondence analysis. The median (range) RLU for buckets used for colostrum harvest, bucket or bottle used for feeding, tube feeders, milking colostrum line, and internal surface of the nipples were 41 RLU (3-1,625 RLU), 78 RLU (<1-3,765 RLU), 29 RLU (<1-2,177 RLU), 83 RLU (<1-9,968 RLU), and 1,101 RLU (2-9,546 RLU), respectively. The first 2 components of multiple correspondence analysis explained 24.7% of data variances and were related to the farms' hygiene and health (13.0%) and feeding practices (11.7% of data variance). The maximal dichotomized luminometry value (<1,000 RLU or ≥1,000 RLU) was associated with hygiene and health dimension. This study gave promising results concerning the potential application of ATP luminometry for calf rearing practices assessment.

Feeding milk supplemented with Ulva sp., Ascophyllum nodosum, or Saccharina latissima to preweaning dairy calves: Effects on growth, gut microbiota, gut histomorphology, and short-chain fatty acids in digesta

Emerging knowledge shows the importance of preweaning nutrition on programming the gastrointestinal microbiome and development of the gut barrier function. The aim of this study was to assess the effects of supplementing cow milk with either intact dried Ulva sp., Ascophyllum nodosum, or Saccharina latissima on growth performance and several gut health parameters of preweaning dairy calves. Forty male Holstein calves were selected based on birth weight (41 ± 4 kg) and plasma Brix percentage (≥8.7%) at d 2 of life. From d 2 to d 42 of life, the control calves (n = 10) were fed with cow milk (8 L/d) without seaweed supplementation, and the experimental calves were fed with cow milk (8 L/d) supplemented with either Ulva sp. (n = 10), A. nodosum (n = 10), or S. latissima (n = 10) at a concentration of 50 g/8 L of cow milk per day (i.e., 5% on a dry matter basis). Calves were weighed every week, and body weight gain and calf starter intake were monitored weekly. At d 42 ± 3 of life, calves were slaughtered. The organ weights and digesta pH from the reticulorumen, mid- and end small intestine, and mid-colon were recorded. A tissue sample (5 cm) collected from the mid-small intestine was analyzed for histomorphology. Digesta from the mid-small intestine and mid-colon were analyzed for lactobacilli, Escherichia coli, and Enterobacteriaceae, and short-chain fatty acid profile. Weight gain of the calves was not affected by seaweed supplementation. Proportional organ weights were not affected by seaweed supplementation except for reticulorumen weight, which was higher in calves fed Ulva sp. Both the mid-small intestinal and mid-colonic digesta populations of lactobacilli, Enterobacteriaceae, and E. coli, as well as the mid-small intestinal histomorphology in seaweed-supplemented calves were not different from control calves. However, acetic acid proportion in mid-colonic digesta was increased in calves fed Ulva sp. and A. nodosum, whereas butyric acid proportion was decreased compared with the control calves. Digesta pH in mid- and end small intestine and mid-colon were not affected, whereas ruminal pH was increased in calves fed Ulva sp. compared with the control calves. In conclusion, intact dried seaweed supplementation did not improve the growth or selected gut health parameters (i.e., histomorphology, digesta pH, bacteria, and short-chain fatty acids) in preweaning Holstein calves.

The adoption of good practices of handling improves dairy calves welfare: Case study

The aim of this study was to assess the effect of the adoption of a set of good practices of handling on dairy calves welfare. Data were retrieved from the records of a commercial farm, considering three periods: Conventional handling (CH, 12 mo.), transitional period (TP, 4 mo.), and good practices handling (GPH, 12 mo.). During CH calves were kept in individual pens, milk-fed in open pails and subjected to abrupt weaning; while during TP and GPH they were kept in groups, milk-fed in nipple-pails, brushed for 5 min. once a day, and subjected to progressive weaning. TP was assumed as a training period necessary for GPH implementation. The percentages of calves treated with antibiotics and numbers of deaths per month were used as indicators of calves welfare. Statistical analysis was performed using a logistic regression model to compare the number of deaths per month between CH and the other periods. Chi-square test was used to compare the percentage of animals treated with antibiotics per month. Results showed that CH had a higher risk of calf's death then TP and GPH, as well as a higher percentage of animals treated with antibiotics. In conclusion, the adoption of good practices of handling improved dairy calves welfare.

Estimating the Rates of Acquisition and loss of Resistance of Enterobacteriaceae to Antimicrobial Drugs in Pre-Weaned Dairy Calves

The objective of this study was to investigate the effect of the antimicrobial drugs (AMD) on the shedding of resistant Enterobacteriaceae in feces of pre-weaned dairy calves. The AMD considered were ceftiofur, administered parenterally, and neomycin sulfate added in milk replacer and fed to calves during the first 20 days of life. Fifty-five calves, aged one to three days, were enrolled and followed to 64 days. Fecal samples were collected three times/week and treatments recorded daily. Enterobacteriaceae were quantified for a subset of 33 calves using spiral plating on plain, ceftiofur supplemented, and neomycin supplemented MacConkey agar. Negative binomial models were used to predict the association between treatment with AMD and the gain and loss of Enterobacteriaceae resistance over time. Acquisition of resistance by the Enterobacteriaceae occurred during treatment and peaked between days three to four post-treatment before decreasing to below treatment levels at days seven to eight post-treatment. Acquisition of neomycin resistance was observed on the first sampling day (day four from the start of feeding medicated milk replacer) to day eight, followed by cyclical peaks until day 29, when the Enterobacteriaceae counts decreased below pre-treatment. Enterobacteriaceae resistance against both AMD increased after AMD administration and didn’t return to pre-therapeutic status until seven or more days after therapy had been discontinued. The study findings provide valuable insights into the dynamics of Enterobacteriaceae under routine AMD use in calves.

A survey of biosecurity and health management practices on Irish dairy farms engaged in contract-rearing

A survey was conducted to investigate potential differences in biosecurity and health management practices on Irish dairy farms that sent their heifers for contract-rearing (source dairy farms, SDF; n = 62) and those rearing their own heifers (control farms, CF; n = 50). Participating farmers were surveyed by postal questionnaire between September and November 2018. The overall response rate was 93%. Results show that structurally, SDF were larger, less fragmented, and more specialized than CF. Outsourcing of labor-intensive activities to external contractors was more common among SDF than CF, exposing them to potentially increased biosecurity risks associated with animal movements, use of shared equipment, and increased frequency of farm visitors. The majority of SDF sent heifers to a single-origin rearing facility (70%), with heifers most commonly arriving at the rearing unit between 2 and 4 mo (53%) and returning to the dairy farm between 18 and 21 mo of age (56%). Despite the increased biosecurity risk associated with contract-rearing, implementation of disease prevention measures was not superior on SDF compared with CF. For both farm types, there was scope for improvement to visitor biosecurity protocols, quarantine procedures, colostrum feeding practices, and hygiene of calving areas. This research provides an overview of the demographics and farm management practices implemented by dairy farmers engaged in contract-rearing of replacement heifers, and will serve to inform farmers, veterinary advisors, and policy makers.

Therapeutic and Prophylactic Effect of the Experimental Bacteriophage Treatment to Control Diarrhea Caused by E. coli in Newborn Calves

The prevalence of antibiotic-resistant bacteria causing neonatal diarrhea in calves has become a serious problem in the control of infection. Due to increasing antibiotic resistance, bacteriophages with probiotics are considered the best alternative. The aim of the study was to evaluate the use of a suppository containing probiotic strains of Lactobacillus spp. and bacteriophages specific for pathogenic E. coli in young calves with diarrhea. The study evaluated therapeutic and prophylactic effects (specific and nonspecific humoral response). The study was carried out on 24 female HF calves, aged 2 to 7 days and weighing from 35 to 46 kg. The calves were divided into four groups (n = 6) as follows: Group 1, healthy control that received no medicine; Group 2, positive control with diarrhea; Group 3, healthy calves that received medicine; Group 4, calves with diarrhea that received medicine. The animals received suppositories containing Lactobacillus spp. and bacteriophages specific for pathogenic E. coli for 5 days. On the first day, the calves received the suppositories twice—in the morning and 12 h later; subsequently they were administered once a day. The health status of the calves was observed for 11 days after the first application of suppositories. A protective and preventive effect of the experimental therapy was obtained in the research. The probiotic-phage suppositories reduced the duration of diarrhea in calves, completely eliminating it within 24–48 h after use. The therapy stimulated the activation of immune mechanisms in calves, which translated into an enhanced specific and nonspecific response and increased resistance to infection.

The Antibiotic Treatment of Calf Diarrhea in Four European Countries: A Survey

Neonatal calves are commonly affected by diarrhea caused by different pathogens, but not always bacteria. Yet, antibiotics are routinely used as a treatment to an unknown extent. It was our goal to survey antibiotic use for the treatment of neonatal calf diarrhea in different countries and to identify influencing factors. A total of 873 farmers and veterinarians in Austria, Belgium, Portugal, and Scotland participated in a voluntary online survey. The data were analyzed using classification and regression tree analyses and chi² tests. Overall, 52.5% of the participants stated that they use antibiotics when treating neonatal calf diarrhea. Of those, 27% use them always, and 45% use highest priority critically important antibiotics. The most important factor differentiating antibiotic use practices was the country the participants were from, which could be due to regulatory differences between the countries. All antibiotic products stated were licensed for use in cattle, but several were not licensed for the treatment of diarrhea in calves. Our study shows that there is an urgent need for more scientific evidence to define best practices for the treatment of neonatal calf diarrhea. Furthermore, consensual criteria for antibiotic therapy must be defined, and targeted training for farmers and veterinarians must be provided.

Effects of delaying increase in milk allowance and type of gradual weaning program on performance and health of calves fed lower levels of milk

The objective of this study was to investigate the effects of delayed increase in milk allowance and type of gradual weaning program on the feed intake, health, and growth of male Holstein calves. Using a 2 × 2 factorial design, each male Holstein calf was randomly assigned to 1 of 2 milk level treatments and 1 of 2 weaning treatments upon arrival to a rearing facility. Calves were either assigned to a moderate (MM) or lower (LM) milk level treatment. All calves received the same milk program from arrival until d 12, increasing from 4 to 5 L/d (115 to 125 g/L) over the 12 d. On d 13, MM calves began receiving additional milk compared with LM calves until they were weaned, with MM offered milk increasing to a peak of 9 L/d (140 g/L). Calves on the MM treatment received a total of 35 kg of milk replacer over 45 d, compared with LM calves, who received a total of 25 kg of milk replacer over 45 d. Calves were also assigned to be weaned by either a 2-step gradual program or a 4-step gradual program. Calves assigned to the 2-step program had their milk reduced in 2 steps from d 30 to 45, and 4-step calves had their milk reduced in 4 steps from d 30 to 45. After d 46, calves received no milk but continued to be monitored until d 59. Calves had ad libitum access to water from arrival, and solid feed was offered from d 5 onward. No interactions of effects of milk level and weaning treatment were detected. By design, calves on the MM treatment consumed greater amounts of milk than LM calves in the preweaning phase from d 13 to 29 (6.1 vs. 4.8 L/d) and weaning phases from d 30 to 45 (4.7 vs. 3.2 L/d). The LM calves consumed greater amounts of solid feed than MM calves from d 22 to 29 of the preweaning phase, and from d 30 to 40 and d 43 to 45 of the weaning phase, whereas postweaning feed consumption was similar for both milk treatments. Calves in both milk treatments had similar blood β-hydroxybutyrate levels, indicating similar rumen development. Body weight and size measurements were similar between milk treatments across the study, although LM calves had a greater average daily gain than MM calves between d 38 and 46 (0.96 vs. 0.71 kg/d). Both gradual weaning treatments resulted in similar feed consumption, growth, and health parameters. Overall, the results indicate that delaying a moderate increase in milk until 12 d after arrival at a rearing facility provided no overall beneficial effect on growth or rumen development.

The effect of neomycin inclusion in milk replacer on the health, growth, and performance of male Holstein calves during preweaning

The prophylactic use of oral antimicrobials, such as neomycin, in milk replacer (MR) or whole milk is a common practice in calf-rearing that is thought to aid in preventing disease. Heavy reliance on antimicrobials is of concern not only because of the development of antimicrobial resistance, but also because of the potentially negative effects on health. The objective of this study was to investigate the effects of neomycin on calf health and growth performance. One hundred and sixty calves (approximately 3-10 d of age), distributed across 2 experimental periods, were stratified by body weight (BW) and serum total protein, and assigned to 1 of 3 treatments: control (CON; nonmedicated MR, n = 60), short-term antibiotic (ST; neomycin mixed in MR from d 1-14, n = 50), or long-term antibiotic (LT; neomycin in ​MR from d 1-28, n = 50). Arrival BW (47.69 ± 0.87 kg) and serum total protein (5.67 ± 0.09 g/dL) were not different between treatment groups. Neomycin in ST and LT was dosed in MR at a rate of 20 mg/kg of BW and was adjusted weekly according to BW. Calf BW was measured weekly for 49 d, and health indicators (fecal score, attitude score, respiratory score, and rectal temperature), MR intake, starter intake, and the use of additional electrolytes and antimicrobials were recorded daily. Calves in the CON group experienced a higher proportion of days with diarrhea (20.32 ± 0.02%) compared with ST (14.70 ± 0.02%) or LT (13.80 ± 0.02%) calves, as well as longer bouts of diarrhea (7.45 ± 0.38 d, 5.69 ± 0.46 d, and 5.62 ± 0.45 d for CON, ST, and LT calves, respectively). Calves in the CON group also experienced higher fecal scores (score of 0.64 ± 0.04) than ST (score of 0.53 ± 0.04) or LT (score of 0.49 ± 0.04) calves, especially at d 7. However, no differences were observed in other health-related measures. The time to reach first diarrhea and first respiratory illness was not different between treatments, nor was the time to recover from respiratory illness. The time to intervention with additional electrolytes or antimicrobials was not different between treatment groups. Furthermore, growth performance, feed intake, and feed conversion ratio were not different. No differences were found when comparing ST and LT, except in the defined daily dose of total antimicrobials received. Calves in the LT group received a higher overall dose than ST calves, and both ST and LT calves received a higher dose than CON calves, which received no prophylactic antimicrobials. Given that there were no differences in performance variables and no additional health benefits aside from reduced fecal scores in calves fed neomycin, current practices involving the use of antimicrobials on dairy and veal operations need to be considered more prudently.

Factors Affecting the Welfare of Unweaned Dairy Calves Destined for Early Slaughter and Abattoir Animal-Based Indicators Reflecting Their Welfare On-Farm

In many dairy industries, but particularly those that are pasture-based and have seasonal calving, "surplus calves," which are mostly male, are killed at a young age because they are of low value and it is not economically viable to raise them. Such calves are either killed on farm soon after birth or sent for slaughter at an abattoir. In countries where calves are sent for slaughter the age ranges from 3-4 days (New Zealand and Australia; "bobby calves") to 3-4 weeks (e.g., Ireland); they are not weaned. All calves are at the greatest risk of death in the 1st month of life but when combined with their low value, this makes surplus calves destined for early slaughter (i.e., <1 month of age) particularly vulnerable to poor welfare while on-farm. The welfare of these calves may also be compromised during transport and transit through markets and at the abattoir. There is growing recognition that feedback to farmers of results from animal-based indicators (ABI) of welfare (including health) collected prior to and after slaughter can protect animal welfare. Hence, the risk factors for poor on-farm, in-transit and at-abattoir calf welfare combined with an ante and post mortem (AM/PM) welfare assessment scheme specific to calves <1 month of age are outlined. This scheme would also provide an evidence base with which to identify farms on which such animals are more at risk of poor welfare. The following ABIs, at individual or batch level, are proposed: AM indicators include assessment of age (umbilical maturity), nutritional status (body condition, dehydration), behavioral status (general demeanor, posture, able to and stability while standing and moving, shivering, vocalizations, oral behaviors/cross-sucking, fearfulness, playing), and evidence of disease processes (locomotory ability [lameness], cleanliness/fecal soiling [scour], injuries hairless patches, swellings, wounds], dyspnoea/coughing, nasal/ocular discharge, navel swelling/discharge); PM measures include assessment of feeding adequacy (abomasal contents, milk in rumen, visceral fat reserves) and evidence of disease processes (omphalitis, GIT disorders, peritonitis, abscesses [internal and external], arthritis, septicaemia, and pneumonia). Based on similar models in other species, this information can be used in a positive feedback loop not only to protect and improve calf welfare but also to inform on-farm calf welfare management plans, support industry claims regarding animal welfare and benchmark welfare performance nationally and internationally.

Antimicrobial use quantification in adult dairy cows - Part 1 - Standardized regimens as a method for describing antimicrobial use

This study describes a process to acquire and convert farm treatment records into a standardized regimen format. Multiple sources of on-farm data were utilized to convert the original treatment records to standardized regimens, enabling the generation of objective, granular descriptions of antimicrobial use. These standard regimen descriptions allow antimicrobial use data to be qualitatively stratified by active substance, disease syndrome treated, use category, and route of administration. Quantitative distributions are available for the grams of active substance per administration, the grams of active substance per regimen, the number of administrations, number of days of therapy and the time frame between the first and last administration. Granular quantification by this method informs future research, surveillance and policy.

Parenteral Antimicrobial Treatment Diminishes Fecal Bifidobacterium Quantity but Has No Impact on Health in Neonatal Dairy Calves: Data From a Field Trial

There is evidence that neonatal calves are over treated with antimicrobials that may disrupt colonization of their gastrointestinal tract (GIT) microbiota. The study objectives were to assess the decision-making process of antimicrobial use on a commercial dairy and impacts of parenteral antibiotics on dairy calves' GIT Bifidobacterium and calf health. Unhealthy pre-weaned dairy calves were enrolled based on farm personnel identification with age-matched healthy calves. Half the calves in each group were treated with a 3-day course of IM ampicillin and half were given supportive therapy as needed. Health scores (appetite, fecal consistency, attitude, and temperature) were recorded twice daily throughout the study. Because of inconsistency in employee health decisions, the 121 enrolled calves were reassessed using objective clinical observations plus fecal dry matter and placed into 1 of 3 health categories: healthy, uncomplicated diarrhea (bright attitude and good appetite but with diarrhea), and sick. Accounting for treatment group allocation, this resulted in six post-enrollment health and treatment categories. Calves were followed daily for 14 days post-enrollment and fecal samples collected at 6 time points and Bifidobacterium was quantified from these samples using quantitative PCR. The objective criteria for disease definition reclassified many "unhealthy" calves as uncomplicated diarrhea. Including all calves, on average, the quantity of Bifidobacterium decreased from the day of enrollment (median 8 days of age) across time to 14 days post-enrollment. Calves given an antibiotic the day of enrollment had a greater decrease in Bifidobacterium 4 and 9 days later relative to enrollment Bifidobacterium compared to untreated calves. At enrollment, sick calves and those categorized as uncomplicated diarrhea were more likely to have low Bifidobacterium counts and less likely to be categorized as healthy following antimicrobial treatment. Our results indicate that relying on farm personnel to identify morbidity may lead to some clinical misclassification. There was no indication that antimicrobials affected subsequent health outcomes, but antimicrobials did impact Bifidobacterium dynamics. These results highlight the importance and difficulty in assigning appropriate illness classification on farms and point to a need to develop better point of care diagnostics that improve calf husbandry and stewardship of antimicrobials.

Survey of perceptions and attitudes of an international group of veterinarians regarding antibiotic use and resistance on dairy cattle farms

Veterinarians are the main source of information for farmers regarding the responsible use of antibiotics in farm animals and how to reduce the risk of antibiotic resistance. Consequently, understanding how veterinarians perceive their clients' and colleagues' antibiotic use and their own beliefs about the development of antibiotic resistance is essential to determining areas in which antibiotic use practices can be improved to minimize the emergence of antibiotic resistance. An international cross-sectional study was carried out using a questionnaire designed to elucidate perceptions, attitudes, and concerns of dairy veterinarians regarding antibiotic use and the emergence of antibiotic resistance in dairy farming. The questionnaire was initially administered to veterinarians attending the International Bovine Mastitis Conference in Milano, Italy, 2018, followed by veterinarian members of the National Mastitis Council, and all conference registrants. A total of 71 participants from 21 countries participated in the survey, the majority were from the United States and member countries of the European Union. Logistic regression analysis was conducted to identify predictors of veterinarians' level of concern about the development of antibiotic resistance on their clients' farms. Associations were described with odds ratios (ORs) and the associated 95 % confidence intervals (95 % CIs). Free text responses where participants shared their views on the reason for overprescribing antibiotics by veterinarians were analyzed using thematic analysis. Participants perceived that nearly half of their clients overuse or inappropriately use antibiotics, and nearly half of their colleagues overprescribe or inappropriately prescribe antibiotics. After controlling for other factors, the odds of veterinarians being concerned about antibiotic resistance on dairy farms they served decreased by a factor of 0.91 for each additional year of participants' experience working with dairy cattle (OR = 0.91, 95 % CI = 0.84-0.99). Participants concerned about antibiotic resistance on clients' dairy farms were also more likely to consider better adherence to drug labelling as important for reducing farmers' antibiotic use (OR = 6.86, 95 % CI = 1.21-38.93). Thematic analysis revealed four themes surrounding the perceived reasons for veterinarians' overprescribing of antibiotics: (i) knowledge, (ii) attitudes, (iii) barriers, and (iv) rules and regulations. The study findings will aid in the development of strategies to improve antibiotic use in dairy farming and educational initiatives looking to enhance the communication between veterinarians and farmers about judicious use of antibiotics.

Particulate matter and airborne endotoxin concentration in calf barns and their association with lung consolidation, inflammation, and infection

Agricultural operations are important sources of organic dust containing particulate matter (PM) and endotoxins, which have possible negative health consequences for both humans and animals. Dust concentrations and composition in calf barns, as well as the potential health effects for these animals, are scarcely documented. The objective of this study was to measure PM fractions and endotoxin concentrations in calf barns and study their associations with lung consolidation, respiratory tract inflammation, and infection in group-housed calves. In this cross-sectional study, samples from 24 dairy farms and 23 beef farms were collected in Belgium from January to April 2017. PM_1.0, PM_2.5 and PM₁₀ (defined as particulate matter passing through a size-selective inlet with a 50% efficiency cut-off at a 1.0-μm, 2.5-μm, and 10-μm aerodynamic diameter, respectively) were sampled during a 24-h period using a Grimm aerosol spectrometer (Grimm Aerosol Technik Ainring GmbH & Co. KG). Endotoxin concentration was measured in the PM₁₀ fraction. Thoracic ultrasonography was performed and broncho-alveolar lavage fluid was collected for cytology and bacteriology. Average PM concentrations were 16.3 µg/m³ (standard deviation, SD: 17.1; range: 0.20-771), 25.0 µg/m³ (SD: 25.3; range: 0.50-144.9), and 70.3 µg/m³ (SD: 54.5; range: 1.6-251.2) for PM_1.0, PM_2.5, and PM₁₀, respectively. Mean endotoxin in the PM₁₀ fraction was 4.2 endotoxin units (EU)/µg (SD: 5.50; range: 0.03-30.3). Concentrations in air were 205.7 EU/m³ (SD: 197.5; range: 2.32-901.0). Lung consolidations with a depth of ≥1, ≥3, and ≥6 cm were present in 43.1% (146/339), 27.4% (93/339), and 15.3% (52/339) of the calves, respectively. Exposure to fine (PM_1.0) PM fractions was associated with increased odds of lung consolidations of ≥1 cm (odds ratio, OR: 3.3; confidence interval (CI): 1.5-7.1), ≥3 cm (OR: 2.8; CI: 1.2-7.1), and ≥6 cm (OR: 12.3; CI: 1.2-125.0). The odds of having lung consolidations of ≥1 cm (OR: 13.9; CI: 3.4-58.8) and ≥3 cm (OR: 6.7; 1.7-27.0) were higher when endotoxin concentrations in the dust mass exceeded 8.5 EU/µg. Broncho-alveolar lavage fluid neutrophil percentage was positively associated with PM₁₀ concentration, and epithelial cell percentage was negatively associated with this fraction. Concentration of PM_2.5 was positively associated with epithelial cell percentage and isolation of Pasteurella multocida. Although concentrations of fine dust are lower in calf barns than in poultry and pig housings, in this study they were associated with pneumonia in calves. Dust control strategies for reducing fine dust fractions in calf barns may benefit human and animal respiratory health.

Zootechnical and health performance of Holstein x Gir crossbred calves

Crossbreeding is used to increase production and disease resistance in adult animals, and there is no research to assess the performance of animals in the early stages. The aim of this study was to evaluate the zootechnical and health performance of Holstein x Gir calves (½ HG: ½ Dutch ½ Gir and ¾ HG: ¾ Dutch ¼ Gir), from birth to 80 days of age, and compare metabolic parameters between groups. In this sense, calves were monitored for zootechnical parameters; epidemiological indexes such as morbidity, mortality, recurrence of diarrhea, pneumonia, and other diseases; as well as serum concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, total proteins, cholesterol, triglycerides, albumin, urea, and paraoxonase1 (PON1). ¾ HG calves showed higher morbidity for diarrhea and remained with diarrhea for longer compared to ½ HG calves, and this was reflected in the average daily weight gain until the 42nd day, with ½ HG calves performing better. There were no differences regarding passive immune transfer between groups, as well as no differences in morbidity and mortality from pneumonia. Regarding biochemical analyses, a difference was found only in the concentrations of PON1, which were higher in ¾ HG calves. The findings show that blood degree influences the occurrence and duration of diarrhea, negatively impacting the zootechnical performance of the animals. Crossbreeding bulls with zebu cattle can be an alternative to increase calf resistance and reduce diarrhea, thus lowering economic losses and improving animal performance.

Quantitative risk assessment of introduction of BVDV and BoHV-1 through indirect contacts based on implemented biosecurity measures in dairy farms of Spain

A stochastic quantitative risk assessment model was developed to estimate the annual probability of introduction of bovine viral diarrhea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) on 127 dairy farms through indirect contacts. Vehicles transporting calves, cattle to slaughterhouse, dead animals, and mixture of feed, as well as visits by veterinarians and hoof trimmers, farm workers and contacts with neighbors were considered in the model. Data from biosecurity questionnaires of each farm, scientific literature and expert opinion from field veterinarians, animal vehicle drivers, hoof trimmers and personnel from rendering transport companies were used to estimate values for input parameters. Results showed that the annual probability of introducing BVDV or BoHV-1 through indirect contacts was very heterogeneous. The overall distribution of median values for each farm ranged from 0.5 to 14.6% and from 1.0 to 24.9% for BVDV and BoHV-1, respectively. The model identified that providing protective clothing and boots to visits, not allowing the animal vehicle driver to come into contact with animals present on the farm and ensuring that calf vehicles arrived empty, were the measures with the highest impact on the probability of infection for most farms. This model could be a useful tool to show the impact of the measures to farmers and veterinarians, thus increasing their awareness on biosecurity. In addition, it could support decision making on which measures should be prioritized in dairy cattle herds to reduce the probability of introduction of diseases.

Hygiene management in newborn individually housed dairy calves focusing on housing and feeding practices

In calf rearing, the first weeks of life are critical and associated with the highest mortality due to enteric and respiratory diseases. A well-implemented hygiene management can help to protect calves' health preventively by reducing the load of pathogenic bacteria and interrupting infection chains. The aim of this study was to identify deficiencies in hygiene management of individually housed dairy calves by surveying current practice and examining feeding and housing equipment with different hygiene indicators. On 11 farms, different locations in 2 pens or hutches for individual calf rearing prepared for restocking and 2 feeding buckets per farm, including the inner and outer surfaces of artificial teats, were visually scored for cleanliness and sampled with swabs (housing equipment: n = 167; feeding equipment: n = 120). The sanitation of floors was tested with sock samples (n = 41). A total of 328 samples were analyzed for adenosine triphosphate (ATP) and protein residues, aerobic total viable count (TVC), total coliform count (TCC), Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase-producing bacteria (ESBL), and Salmonella spp. After evaluation of these results, the farmers were informed about the findings and trained on improvement in hygiene management personally. The sampling was repeated after 1 year to detect possible changes in hygiene management. The highest bacterial loads (TVC, TCC, and E. coli) were observed in feeding equipment, especially the inner teat of milk feeding buckets. Environmental samples, primarily the sidewalls and back walls of tested pens and hutches, exhibited the lowest bacterial counts and ATP and protein residues. All samples were negative for MRSA and Salmonella spp. In 10.5% of all samples, ESBL was detected, and in 6.8%, ESBL E. coli was detected, predominately in sock samples, followed by feeding equipment samples. Training in hygiene management showed only limited effects. In conclusion, there is still great potential to improve the implementation of hygiene measures in individual calf housing. In particular, more attention should be paid to the cleaning of feeding buckets and artificial teats, as this is a simple means of interrupting the possible spread of pathogens among calves.

Invited review: Academic and applied approach to evaluating longevity in dairy cows

In its simplest form, longevity is defined as the ability to live a long life. Within the dairy industry, longevity has been defined and measured in many different ways, and the aim of this review is to disentangle the definitions and provide some clarity. Using a more standardized approach for defining and measuring longevity, both in academic discussions and on-farm application, we suggest using herd life (days) for time from birth until culling, and length of productive life (days) for time from first calving until culling. Despite identified benefits of extending the length of productive life, global trends in the time spent by dairy cattle in the herd have mostly been negative. Factors influencing herd life, such as health, rearing, environmental conditions, and management, are often ignored when longevity goals are evaluated, thereby underestimating the effect these factors have on defining overall longevity. Also, production efficiency, herd profitability, and welfare are not necessarily served by the longest life but rather by the optimized length of herd life instead. The majority of research has focused on the role of genetics on longevity. In this review, we provide insight into influences affecting dairy cow herd life as well as farm- and cow-level factors associated herewith. Finally, we suggest using herd life, including reproduction, production, health, and youngstock performance, for farm-level evaluation and length of productive life for time spent in the lactating herd.

Technical note: Is fecal consistency scoring an accurate measure of fecal dry matter in dairy calves?

The objective of this cross-sectional study was to evaluate the accuracy of fecal consistency scoring as a measure of fecal dry matter (DM) in dairy calves. This study was conducted at a commercial grain-fed veal facility in southwestern Ontario. A total of 160 calves arrived at the facility in 2 groups of 80 calves each. Calves were fed milk replacer twice daily at 0700 and 1700 h and had ad libitum access from arrival onward to water through nipple drinkers and starter through a shared trough. Fecal consistency scores were evaluated once daily in the first 28 d after arrival before milk feeding. The fecal consistency scoring was conducted using a 4-level scoring scale: 0 = normal (firm but not hard); 1 = soft (does not hold form, piles but spreads slightly); 2 = runny (spreads readily); and 3 = watery (liquid consistency, splatters). Fecal samples were collected from all calves via rectal palpation on d 1, 7, 14, and 21 at 0900 h for determination of fecal DM. Mixed repeated measures linear regression models were built to assess the accuracy of fecal consistency scoring in predicting fecal DM. Over 4 selected time points (d 1, 7, 14, and 21) the 160 calves were observed, 382 (61.6%) had a fecal consistency score of 0, 121 (19.5%) had a score of 1, 85 (13.7%) had a score of 2, and 32 (5.2%) had a score of 3. A fecal score of 0 had a fecal DM of 25.1 ± 8.4%, whereas a fecal score of 1 had a DM of 21.8 ± 8.2%. With respect to calves that had a fecal score of 2 or 3, their fecal DM was 16.0 ± 11.1% and 10.7 ± 6.9%, respectively. In evaluating the pairwise comparisons generated in the repeated measures model that controlled for day of sampling, a fecal score of 0 had a 3.2%, 8.1%, and 12.0% higher fecal DM, respectively, when compared with those that had a fecal score of 1, 2, and 3. In addition, calves with a fecal score of 1 had a 5.0% and 8.8% higher fecal DM than calves with a fecal score of 2 and 3, respectively. Finally, calves with a fecal score of 2 had a 3.8% higher fecal DM than those with a fecal score of 3. This study confirms that using observational fecal consistency scoring can accurately predict diarrhea or a decline in fecal DM.

Influence of early use of antimicrobial on the health and performance of Holstein calves in the first month of life

ABSTRACT: The early use of antimicrobial therapy has been introduced in many farms to prevent diarrhea and respiratory disease in young calves; however, there is controversy about whether this practice has a beneficial effect on the health of these animals. This study evaluated the influence of the early use of antimicrobials on the health and performance of neonatal Holstein calves. Twenty-six Holstein calves were screened and divided into two groups, according to the administration (ATB+), or not (ATB-) of tulathromycin (2.5mg/kg, subcutaneously) within the first 12 hours of life. Calves were evaluated by general clinical examination, fecal score, respiratory score, and external palpation of the umbilical region, besides fecal output of dry matter. Anemia was determined by using an automatic system and, also, using a commercial kit for iron dosage. Diarrhea was diagnosed by a centrifuge-flotation technique using a sugar solution (Cryptosporidium) and multiplex semi-nested RT-PCR (rotavirus/coronavirus). The performance of the calves was estimated by Daily Weight Gain (DWG). The young dairy calves were evaluated within 12 hours of birth (≤12h) and at 3-5th (D3-5), 7-9th (D7-9), 13-15th (D13-15), 20-23rd (D20-23), and 27-30th (D27-30) days of life. No difference was noted between the ATB+ and ATB- groups concerning heart rate, respiratory frequency, and rectal temperature. Erythrogram showed a higher frequency of anemia in ATB- group (P=0.016) at the D3-5 check-up; lower values of serum iron were also observed simultaneously (P=0.051). Thirteen cases of respiratory disease were detected during this study; however, no significant difference was observed between the groups in this regard. The frequency of diarrhea (fecal score 2-3) was high in both groups, peaking at D13-D15. No differences were noted between the groups regarding the frequency of diarrhea when considering the dry fecal matter. The predominant etiological agent for diarrhea was Cryptosporidium spp.. The DWG was similar between groups, with maximum weight reduction on D13-15. The administration of tulathromycin in prophylactic dose (2.5mg/kg) at birth decreased the frequency of anemia but did not influence weight gain or the prevalence of diarrhea.

Invited Review: Nutritional regulation of gut function in dairy calves: From colostrum to weaning

Purpose

Published literature regarding calf nutrition was reviewed to create an information base for the implementation of proper nutritional management to maximize health and productivity.

Sources

The main source of data and information for this review was peer-reviewed literature.

Synthesis

Feeding a sufficient volume of colostrum during the first hours of life is crucial to calf health and survival; however, less is known about transition milk feeding and the potential benefits of the myriad of bioactive compounds it contains. After feeding colostrum and transition milk, calves are susceptible to diarrhea when moved onto high amounts of milk, and antibiotic use is often necessary to decrease disease. Feeding an elevated plane of milk nutrition results in increased ADG and, in some studies, increased future milk production. Thus, this nutritional strategy is recommended; however, weaning calves from high volumes of milk represents massive changes in the structure and microbiology of the gastrointestinal tract.

Conclusions and Applications

Colostrum and transition milk contain an abundance of bioactive molecules that can positively affect gut development and microbiota. There is significant potential for the use of novel feeding strategies and microbial-based products as alternatives to antibiotics. Calves fed an elevated plane of nutrition in the first month of life have greater productivity and growth. However, weaning should take place later in life. Moreover, applying a proper step-down feeding protocol is recommended, as it allows calves to intake and digest sufficient solid feed for growth and minimize distress at weaning.

Growth performance, nutrient utilization, and health of dairy calves supplemented with condensed whey solubles

Our objective was to evaluate growth performance, nutrient utilization, and health of calves supplemented with condensed whey solubles (CWS). Twenty-four Holstein calves (2 d old) in hutches were used in a 12-wk randomized complete block design study. Calves were blocked by birth date and sex. Treatments were (1) control (CON) with no supplement and (2) 50 g/d of CWS. Preweaning CWS was fed with milk and postweaning CWS was top-dressed on starter pellets. Calves were fed 2.83 L of pasteurized milk 2×/d during wk 1 to 5, 1×/d in wk 6, and weaned at d 42. Calves had ad libitum access to starter pellets and water. Individual intakes of milk and starter pellets were measured daily. Fecal scores (0 = firm, 3 = watery) and respiratory scores (healthy ≤3, sick ≥5), calculated from the sum of scores for rectal temperature, cough, ocular, and nasal discharge, were recorded daily. Body weights (BW), frame growth, and jugular blood samples were taken once every week at 3 h after the morning feeding. Fecal grab samples were collected in wk 12 for analysis of apparent total-tract digestibility. Data were analyzed using MIXED procedures of SAS 9.4 (SAS Institute Inc., Cary, NC) with repeated measures. Total dry matter intake was greater in calves fed CWS compared with CON. Calves fed CWS tended to have greater BW during the postweaning period. Gain:feed, average daily gains, withers heights, and concentrations of plasma urea nitrogen were not different. Concentrations of plasma β-hydroxybutyrate were greater in calves fed CWS compared with CON. Serum glucose concentrations were greater in calves fed CON during the preweaning stage, but similar concentrations were found between treatments during the postweaning stage. Rumen pH, ammonia-N, and total volatile fatty acids were similar between treatments. The acetate:propionate ratio was greater in calves fed CWS. The apparent total-tract digestion of nutrients was similar; however, CON tended to have greater digestion of neutral detergent fiber. Fecal scores were not different, but a treatment by week interaction was observed. Supplementing CWS improved starter intake, postweaning BW, β-hydroxybutyrate, fecal scores, and maintained frame growth.

A retrospective cohort study comparing dairy calf treatment decisions by farm personnel with veterinary observations of clinical signs

Antimicrobials are frequently administered to calves with diarrhea, despite evidence suggesting questionable efficacy. Even if efficacious, providing the appropriate therapy to an animal requires accurate disease detection. The objective of this study was to use previously collected data and compare clinical scoring by a veterinarian to treatment decisions by on-farm personnel. Data describing daily clinical scores and farm treatments were previously collected from 4 farms for calves from birth to age 28 d. In this data set, a total of 460 calves were enrolled. Daily observations and clinical assessments were made on each farm by the same veterinarian, for a total of 12,101 calf observation days. Farm personnel made all treatment decisions based on their own observations, and these treatments were recorded by study personnel. Overall, the cumulative incidence of a calf exhibiting at least one abnormal clinical sign over the 28-d observation period was 0.93, with cumulative incidences of 0.85 and 0.33 for diarrhea and dehydration, respectively. The cumulative incidence of any treatment (including antibiotics and electrolytes) was 0.85, although the majority of treatments used an antimicrobial. The farm-specific probabilities that a calf with clinical signs of dehydration or diarrhea, respectively, received fluid or electrolyte therapy ranged from 0.08 to 0.27 and 0.03 to 0.12. These probabilities were greater for the day a clinical sign was first observed. The farm-specific probabilities that a calf with clinical signs of diarrhea received an antimicrobial was 0.23 to 0.65, and the probability that a calf exhibiting clinical signs of respiratory disease received an antimicrobial was 0.33 to 0.76. The first observation of diarrhea had similar probabilities to those for all observations of diarrhea. There was greater probability of treatment for calves with their first observed abnormal respiratory signs. Probabilities that treatment with antimicrobials, or fluids or electrolytes, was associated with an abnormal clinical sign were low-that is, calves received treatments in the absence of any abnormal clinical signs. This study illustrates incongruity between treatment decisions by calf treaters (the designated personnel on each farm responsible for calf health assessment and treatment decisions) and those of an observer using a clinical scoring system to identify calves with abnormal clinical signs. These findings indicate opportunities and the need for dairy farmers and advisors to evaluate calf treatment protocols, reasons for treatment, and training programs for calf health and disease detection, as well as to develop monitoring programs for treatment protocol compliance and health outcomes following therapy.

Control of bovine respiratory disease, with and without co-morbidity by otitis media, in dairy heifers comparing gamithromycin, tulathromycin, or no medication at a commercial development facility

The objective of this study was to evaluate one strategy for control (metaphylaxis) of bovine respiratory disease, with and without co-morbidity with otitis media, in dairy heifers at a commercial development facility. Individual heifers were the experimental unit. At weaning, 1 of 3 experimental treatments (gamithromycin, tulathromycin, or no medication) was randomly assigned to 1,567 heifers from 11 different dairies. Gamithromycin was administered to 631 heifers, tulathromycin was administered to 621 heifers, and no medication was administered to 315 heifers (negative control). Heifers were then commingled and penned according to body weight. Each pen contained heifers from each group, and periodically, larger numbers of heifers were penned together. All heifers were observed for the subsequent 42 d and treated according to protocols prescribed for the facility. Morbidity due to respiratory disease was less for heifers medicated with gamithromycin than for heifers medicated with tulathromycin. Morbidity due to respiratory disease was less for heifers medicated with gamithromycin than for heifers in the negative control group. Fewer heifers medicated with either antimicrobial were subsequently treated because of co-morbidity with otitis media. Mortality was not different among the treatment groups. Heifers medicated with either antimicrobial had greater average daily gain than did heifers in the negative control group.

Space allowance influences individually housed Holstein male calves' age at feed consumption, standing behaviors, and measures of immune resilience before and after step-down weaning

Many dairy calves in the southwestern regions of the United States are raised in wooden hutches with 1.23 m² of free space that house 3 calves individually. Producers claim that calves in hutch systems are not ready to wean and be placed in groups at the country-average age of 6 wk. Calves may remain in this individual housing system until as late as 10 wk of age. The objective of this study was to modify space allowance of hutches and evaluate weaning readiness using age at solid feed consumption, standing behaviors, and measures of immunity. Calves were randomly assigned at 4 d of age to conventional (CONV; 1.23 m² of space; n = 18), moderate (MOD; 1.85 m² of space; n = 17), or maximized (MAX; 3.71 m² of space; n = 19) space allowance in hutches. These modifications also changed the number of calves housed per hutch from 3 (CONV) to 2 (MOD) and 1 (MAX). Calves were fed milk replacer via bottle twice daily until weaning and offered ad libitum feed throughout the experiment. Step-down weaning was initiated (Wi) at age 53 or 54 d by withdrawal of the p.m. bottle and was completed (Wc) 11 d later by removal of the a.m. milk replacer. Accelerometer data for standing behaviors were collected relative to Wi (3 consecutive days to represent -4 wk, -3 d, 3 d, and 3 and 5 wk). Blood samples were collected in the a.m. just before Wi (d 0) and at d 3, 11, 14, and 18 after Wi. Calves provided with more space (MOD and MAX) compared with CONV calves consumed feed at an earlier age and had slightly healthier erythrocytes, greater circulating glucose, and fewer circulating eosinophils. The CONV calves had haptoglobin (Hp) responses to the stressors of both Wi and Wc and had more IFN-γ from whole blood stimulated with phytohemagglutinin-P. The MAX calves had the least active neutrophils (phagocytosis and oxidative burst), but MOD calves' leukocytes secreted the most TNF-α from whole blood stimulated with lipopolysaccharide. Just before and after weaning, MAX calves spent more time per day in the standing position than CONV and MOD calves and had an Hp response to Wc, but MOD calves did not have an Hp response to Wi or Wc. Based on these results, MOD calves were the most ready for weaning; therefore, they potentially can be moved to group housing at an earlier age than CONV calves, thus improving animal welfare concerns over space allowance and individual housing.

Effects of milk replacer feeding rate and long-term antibiotic inclusion in milk replacer on performance and nutrient digestibility of Holstein dairy calves up to 4 months of age

The objectives of this study were to evaluate calf performance and diet digestibility when feeding a milk replacer (MR; 25% crude protein, 18% fat, dry matter basis) at a moderate (MOD) and high (HI) rate, along with MOD with neomycin-oxytetracycline inclusion (1.43 each g/kg; NTMOD). Male Holstein calves (n = 48; 45 ± 1.0 kg of body weight; 3 to 4 d of age) were housed in individual pens for 56 d. All calves were initially fed 0.66 kg of dry matter from MR for the first p.m. and following a.m. feeding, then randomly assigned to 1 of 2 feeding programs: (1) 0.66 kg of dry matter/d for first 39 d divided into 2 equal a.m. and p.m. meals and 0.33 kg for 3 d fed once daily in the a.m. feeding only (MOD, NTMOD); (2) 0.85 kg of dry matter/d for the first 4 d divided into 2 equal a.m. and p.m. meals, 1.07 kg of dry matter/d for the next 31 d divided into 2 equal a.m. and p.m. meals, and 0.48 kg for 7 d fed once daily in the a.m. feeding only (HI). Calves were fed a textured starter containing whole grains (20% crude protein, 43% starch, dry matter basis). Fecal samples were collected for 5 individual calves per treatment between d 47 to 51 to estimate digestibility. Calves were moved into groups by treatment (4 calves/pen) at 56 d and fed the same starter blended with 5% hay until d 112. Data were analyzed as a completely randomized design with repeated measures when applicable using mixed models. Milk replacer dry matter intake averaged 27.4 kg for MOD and NTMOD and 40.3 kg for HI per calf. Preweaning starter intake was less for calves fed HI versus MOD. Preweaning calf BCS change was greater for calves fed HI versus MOD. Preweaning medical treatment days were fewer for calves fed NTMOD versus MOD. Postweaning starter intake was less for calves fed HI versus MOD. Postweaning average daily gain was less for calves fed NTMOD versus MOD. Over the 56-d nursery trial, calves fed HI had less starter intake than calves fed MOD. Digestibility of dry matter, organic matter, acid detergent fiber, and neutral detergent fiber were greater for calves fed MOD versus NTMOD or HI during d 47 to 51 postweaning. Additionally, digestibility of fat was greater for calves fed MOD versus HI. During d 56 to 112, hip width change was greater for calves fed MOD versus NTMOD or HI. Over 0 to 112 d, body weight gain was 100, 98, and 102 kg, whereas hip width change was 10.2, 9.0, and 9.2 cm for calves fed MOD, NTMOD, and HI, respectively. Any preweaning improvements from feeding NTMOD or HI over MOD were lost during the postweaning period, which could be partially explained by reductions in diet digestibility.

A 100-Year Review: Calf nutrition and management

The first calf paper, published in the May 1919 issue of the Journal of Dairy Science (JDS), described factors affecting birth body weight of different breeds of calves. Other studies were done on nonmilk ingredients, growth charts were developed, and early weaning was followed to conserve milk fed to calves. Calf papers did not report use of statistics to control or record variation or to determine whether treatment means were different. Many experiments were more observational than comparative. Typically fewer than 5 calves, and sometimes 1 or 2 calves, were used per treatment. During the next 20 yr, calf studies increased and included colostrum feeding, milk and milk replacer feeding, minerals and vitamins, and fats and oils. Many concepts fundamental to current knowledge and understanding of digestion, rumen development, and milk replacer formulation were developed during this period. In addition, the concept of using antibiotic growth promoters in dairy calf diets was first evaluated and developed during the 1950s. During the 20-yr period of January 1957 through December 1976, a large number of universities in the United States and 1 in Canada contributed almost 150 papers on a variety of calf-related topics. These topics included genetics, physiology of the calf, review of calf immunity, antibiotic feeding, and milk replacer ingredients. This became the golden era of calf rumen development studies, which also engendered studies of calf starter rations and ingredients. A classic review of management, feeding, and housing studies summarized research related to calf feeding and management systems up to that point with an emphasis on maintaining calf growth and health while reducing labor and feed costs. It was also during this period that metric measurements replaced English units. In the 20-yr period from 1977 to 1996, more than 400 articles on calf nutrition and management were published in JDS. With the growing research interest in calves, a paper outlining standardized procedures for conducting and reporting data from calf experiments was first published. A very active area of calf nutrition research from the late 1970s to the mid 1980s was colostrum quality, feeding, and preservation; more than 60 such research articles were published in the journal during this time. Various nonmilk protein sources were evaluated. Extensive studies were done evaluating trace and major mineral requirements in calves along with some vitamin studies. Throughout the 1970s, 1980s, and 1990s, the primary objective of most calf research was how to wean healthy, adequately grown calves at an early age-generally less than 30 d of age. This program was reviewed in a 1979 publication. Research on calf starter ingredients, nutrient composition, and additives was minimal in the 1980s and 1990s given the importance of starter intake to the success of early weaning, but the role of water intake in starter intake and growth was established. Research on issues with calves continued to increase during the last 20-yr period as evidenced by publication of more than 580 articles in JDS as well as many more in other refereed journals. In addition to papers contributed by several universities in the United States and Canada, the number of papers authored by scientists at universities and institutes in other countries increased dramatically during this period. Factors influencing colostral antibody absorption, heat treatment of colostrum, and efficacy of colostrum supplements and replacers were reported. Most studies in this period related to nutrition. Studies were published supporting greater neonatal growth rates from feeding more milk replacer but with a higher crude protein content than traditional. Protein energy effects on growth and body composition were evaluated in concert with greater growth rates. Milk and nonmilk protein sources in milk replacers along with AA supplementation were evaluated. Limited studies were done with fat sources and fatty acid supplementation along with trace minerals and fat-soluble vitamins. Waste milk feeding and heat treatment became more prevalent. Studies established starter ingredient palatability and use of forage when fed with pelleted starters. With the advent of automatic milk and milk replacer feeders, factors influencing how and when to wean were established. Research programs established factors affecting calf behavior and welfare. Several databases were evaluated along with various published studies, and established calf growth during the first 2 mo was subsequently reflected in first- and later-lactation milk production of those calves. A new area of calf research that emerged from 1997 on was the effects of maternal environment and nutrition on calf health, growth, and future productivity. From a mechanistic standpoint, the field of epigenetics seems likely to explain many of these phenomena. Some possibilities for future calf nutrition and management were elaborated.

Preweaned heifer management on US dairy operations: Part I. Descriptive characteristics of preweaned heifer raising practices

The objective of this study was to describe preweaned dairy heifer calf management practices on dairy operations across the United States that were used to analyze factors associated with colostrum quality and passive transfer, Cryptosporidium and Giardia, morbidity and mortality, and average daily gain. This study included 104 dairy operations in 13 states that participated in the National Animal Health Monitoring System's Dairy 2014 calf component study. This 18-mo longitudinal study focused on dairy heifer calves from birth to weaning, and data were collected on 2,545 heifer calves. Descriptive statistics were generated regarding colostrum feeding, preweaning housing, milk feeding and consumption, growth, morbidity and mortality, and weaning practices. The majority of calves enrolled were Holsteins (89.4%). Over half the calves (63.2%) enrolled in the study received the majority of their colostrum via bottle; however, 22.1% of calves from 51.0% of operations received colostrum via suckling from their dams. For all calves, the mean time to the first colostrum feeding was 2.8 h, and the average amount of colostrum at the first feeding was 2.9 L, with 4.5 L provided in the first 24 h. The mean serum IgG of all calves was 21.7 g/L; however, 76.0% of operations had at least 1 calf with failure of passive transfer of immunity with a serum IgG below 10 g/L. The majority of calves in the study were housed individually (86.6%). Nonetheless, 20.2% of operations housed some calves in groups, representing 13.4% of all calves. Approximately one-half of the calves in the study (52.3%) were dehorned or disbudded during the preweaning period, with only 27.8% of these calves receiving analgesics or anesthetics during the procedure. Whole or waste milk was the liquid diet type fed to 40.1% of calves, and milk replacer was fed to 34.8% of calves. A combination of milk and milk replacer was fed to 25.1% of calves. Calves, on average, were fed 2.6 L per feeding and fed 2.6 times/d, resulting in a total of 5.6 L of liquid diet fed per day. The mean average daily gain for all calves enrolled in the study was 0.7 kg/d. Fecal samples were collected and almost all operations had at least 1 calf positive for Cryptosporidium (94.2%) or Giardia (99.0%), and 84.6% of operations had calves that tested positive for both Cryptosporidium and Giardia. Over one-third of calves (38.1%) had at least one morbidity event during the preweaning period and the mortality rate was 5.0%. The mean age at weaning was 65.7 d. This study provides an update on dairy heifer raising practices in the United States.

Dairy calf rearing unit and infectious diseases: diarrhea outbreak by bovine coronavirus as a model for the dispersion of pathogenic microorganisms

Dairy calf rearing unit is a management system that is only recently being implemented by some milk producer’s cooperatives in southern Brazil. However, aspects related to the health profile of the heifer calves that arrive in the rearing unit as well as about biosecurity practices and microbiological challenges have not yet been evaluated in this rearing system in a tropical country. Diarrhea is the main and most frequent consequence of enteric infections in newborn calves. This study, through some etiological and epidemiological characteristics of an outbreak of neonatal diarrhea, has the aim to alert to the possibility of pathogenic microorganism spread in a dairy heifer calf rearing unit. The diarrhea outbreak presented some non-regular characteristics observed in bovine coronavirus (BCoV) enteric infections in dairy calves. The spread of infection was extremely rapid (1 week); the attack rate (> 50%) was much higher than that observed in calves subjected to conventional rearing; and the age range (5 to 90 days) of the affected heifer calves was much broader than that often observed in the BCoV diarrhea worldwide. These unusual epidemiological characteristics observed in this BCoV diarrhea outbreak raise awareness of the health threat present in calf rearing units as well as of the easy and rapid viral spread in a population of young animals from different dairy herds and, therefore, with very distinct immunological status.

Ecological Restoration of Antibiotic-Disturbed Gastrointestinal Microbiota in Foregut and Hindgut of Cows

Antibiotically disturbed gastrointestinal microbiota needs a long period time to be restored to normal, which may cause a series of problems to the host. The understanding of restoration of the biased microbiota by antibiotics remains largely unknown. Here, we investigated the microbiota shift in foregut (rumen) and hindgut (rectum) of lactating cows after antibiotics exposure as well as after antibiotics withdrawal with (Microbiota transplantation, MT group) or without (Control, CON group) microbiota transplantation. We were able to demonstrate that microbiota in both foregut and hindgut significantly changed after 3 or 14 days of antibiotics exposure, and the changes persisted over long period of time (>18 days) after withdrawing the antibiotics. We further observed a faster restoration of microbiota in both foregut and hindgut of MT group than CON group, microbiota in foregut was mainly benefited from microbiota transplantation by restoring the alpha-diversity as well as within-group similarity, while microbiota in hindgut was primarily benefited from microbiota transplantation by reestablishing the co-occurrence network (nodes number, edges number, density, modularity as well as closeness centrality). These results together expanded our understanding of restoration of the biased microbiota by antibiotics, and may also be instructive to deal with the delayed microbiota restoration at least in cows.

Implementation of an algorithm for selection of antimicrobial therapy for diarrhoeic calves: Impact on antimicrobial treatment rates, health and faecal microbiota

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Use of an algorithm for treatment of diarrhoeic calves resulted in a reduction of 80% in antimicrobial treatment rates.

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The reduction of antimicrobial treatment rates in diarrhoeic calves did not have a negative impact on the health of the calves.

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Changes in management practices on dairy farms can have a positive impact on the faecal microbiota of healthy calves.

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Changes in management practices in dairy farms may affect the faecal microbial diversity of healthy calves.

This study evaluated the impact of an algorithm targeting antimicrobial therapy of diarrhoeic calves on the incidence of diarrhoea, antimicrobial treatment rates, overall mortality, mortality of diarrhoeic calves and changes in the faecal microbiota. The algorithm was designed to target antimicrobial therapy in systemically ill calves from on two dairy farms. Retrospective (farm 1: 529 calves; farm 2: 639 calves) and prospective (farm 1: 639 calves; farm 2: 842 calves) cohorts were examined for 12 months before and after implementation of the algorithm. The Mantel–Haenszel test and Kaplan–Meier survival curves were used to assess the cumulative incidence risk (CIR) and time to development of each outcome before and after implementation of the algorithm. The CIR of antimicrobial treatment rates was 80% lower after implementation of the algorithm on both farms (CIR 0.19, 95% confidence interval 0.17–0.21). There was no difference in the CIR of overall mortality, but the CRI for mortality of diarrhoeic calves was lower in the period after implementation of the algorithm on one farm. The faecal microbiota of 15 healthy calves from both farms at each time period were characterised using a sequencing platform targeting the V4 region of the 16S rRNA gene. On both farms, there were significant differences in community membership and structure (parsimony P < 0.001). Use of the algorithm for treatment of diarrhoeic calves reduced antimicrobial treatment rates without a negative impact on the health of calves. However, the experimental design did not take into account the potential confounding effects of dietary changes between the study periods.

Quantitative and qualitative analysis of antimicrobial usage in white veal calves in France

The development of antimicrobial resistance has made it necessary to measure antimicrobial usage in animal production sectors. France is a major European producer of white veal calves, but few data were previously available for that sector, even though these young animals are particularly susceptible to infection and considered as a reservoir of antimicrobial resistance. A cross-sectional study was conducted on 186 batches of French calves to estimate the exposure of white veal calves to antimicrobials and identify the potential risk factors related to antimicrobial usage. An indicator of calf exposure was calculated as a count of the number of antimicrobial treatments per calf. The indicator was based on veterinary prescriptions (products, quantity dispensed and dosage prescribed) and the estimated weight of calves at treatment, using the dates of treatment collected from farm registers. The study showed that calves were exposed to an average of 8.55 antimicrobial treatments (SD: 2.21, range: 2.75-15.86) over the five to six months of the fattening process. Group treatments were predominant (95.8%) and administered by the oral route. The "starting treatments", given during the first two weeks of the fattening period, were administered systematically (to all the calves in all the farms) and accounted for a third of all treatments. Tetracyclines, polypeptides and macrolides were the most widely used antimicrobials, with respectively 4.32, 1.59 and 1.01 treatments per calf. Only rare uses of 3rd and 4th generation cephalosporins and fluoroquinolones, considered as critically important in human medicine, were reported. Despite low variability of exposure between farms, a linear mixed-effects model highlighted a higher variability between farmers (ICC=0.14) or veterinarians (ICC=0.12), than between integrators (ICC=0.06). The number of calves per pen, introduced as a fixed effect in the model, was also significant: calves housed in pens of 6-10 and fed in buckets had on average 2.55 more antimicrobial treatments per calf than calves housed in pairs with the same feeding system. The model also highlighted an increase of 1.48 treatments per calf for farms with more than five percent of mortality, versus those with two percent or less. The present study showed that antimicrobial treatments are numerous in veal calf fattening farms, particularly at the arrival of the animals. Taking into account the development of resistance to antimicrobials, the necessity and the effectiveness of some of these treatments should be re-evaluated.

INVITED REVIEW: Farm size and animal welfare

Critics of agricultural intensification have argued that the transition from smaller to larger farms has compromised animal welfare. To critically examine evidence relevant to this claim, we reviewed more than 150 publications that examined the relationship between farm size and at least one animal welfare indicator. Although much of this literature focuses on dairy cattle, we also reference other farmed species where appropriate. We found little evidence of any simple relationship, negative or positive, between farm size and animal welfare. Instead, the evidence suggests that larger farms provide some opportunities to improve animal welfare but may also create welfare risks. For example, larger farms permit more specialized and professional management of animal health but can make it more difficult to accommodate outdoor access that some view as integral to animal welfare. Future research should attempt to specify the underlying casual mechanisms by which statistical associations between farm size and indicators of welfare are believed to occur. We also suggest that policy and advocacy efforts aimed at reversing increases in farm size would be better directed toward improving welfare on farms of all sizes.

Prophylactic use of a standardized botanical extract for the prevention of naturally occurring diarrhea in newborn Holstein calves

The objectives of this study were to evaluate the prophylactic use of SB-300 (Jaguar Animal Health, San Francisco, CA), a standardized botanical extract isolated from the bark latex of Croton lechleri, on reducing fecal water losses and diarrhea events in Holstein bull calves individually housed under a restricted whole-milk feeding regimen (6 L/d) from 1 to 25 d of life. Fluid therapy administration due to dehydration, average weight gain, and the fecal microbiome were also evaluated. Bull calves used in this study were born from normal parturition, fed 4 L of pooled pasteurized colostrum by esophageal feeder, and moved to a research facility at Cornell University (Ithaca, NY). A double-blinded randomized clinical trial was designed to allocate a total of 40 newborn calves into 1 of 2 treatment groups: calves receiving (twice daily) a solution containing 500 mg of SB-300 added to the whole milk for the first 15 d of life (SB-300, n = 20) or a control group receiving sterile water added to whole milk for the same period (CTR, n = 20). Treatment solutions had a total volume of 10 mL per treatment. Data regarding fecal dry matter were collected to precisely measure water content in fecal samples and to define diarrhea events; the SB-300 group had significantly increased fecal dry matter during the study period. Additionally, significantly fewer events of diarrhea were observed for calves in the SB-300 group (16.9%) compared with calves in the CTR group (46.5%). Dehydration status was evaluated and treated accordingly; calves with moderate dehydration were offered oral electrolytes, and calves with severe dehydration were rescued with intravenous fluid therapy. Calves in the SB-300 group had fewer intravenous fluid therapies administered during the study period (1.6%) compared with the CTR group (3.1%). Overall fluid therapy administered (oral electrolytes plus intravenous fluids) was significantly higher for the CTR group (9.2%) compared with the SB-300 group (6.1%) during the study period. No differences in milk consumption, calf starter intake, or weight gain were observed between treatment groups. A single time increase in Bifidobacterium was observed on d 20 of life for the SB-300 group; otherwise, no differences in fecal microbiome profile were detected between treatment groups. These results suggest that 500 mg of SB-300 added to the milk for 15 d can reduce the incidence of diarrhea and reduce severe dehydration in milk-fed calves.

Invited review: A systematic literature review and meta-analysis of mortality and culling in dairy cattle

Dairy industries and individual farmers are concerned about mortality and culling of dairy animals. This is because the timing and fates of animals that exit dairy farms have important animal welfare and economic consequences that reflect the conditions under which they are farmed and the efficiency of their production systems. Reports from a few countries have indicated increased incidence of mortality, and occasionally culling, of dairy animals in recent decades, and these changes have been associated with intensification of production systems. Dairy industries and farmers need benchmarks for culling and mortality against which they can compare themselves, as well as improved understanding of the extent of any change and of any associated factors. We reasoned that a systematic literature review and meta-analysis of scientific articles published between 1989 and 2014 would allow us to determine whether these reports were universal, to quantify any change over time, and to investigate whether production systems or study factors were associated with culling and mortality. From 3,275 articles retrieved from databases and manual searching of cited articles, 118 articles were appraised independently by 2 assessors, and 51 articles representing 54 studies were determined to be eligible for review and meta-analysis. We estimated that both the annual incidence risk (IR) and incidence density of mortality of cows had increased significantly from 0.02 per cow and 2.32 per 100 cow-years, to 0.04 per cow and 3.75 per 100 cow-years, an increase per decade of 0.02 per cow and 1.42 per 100 cow-years, respectively. We also estimated that the annual IR of culling attributed to low production had declined significantly from 0.07 to 0.05 and that the IR of perinatal, but not neonatal, mortality had increased significantly from 0.04 to 0.06 per decade. We found no evidence of change in overall annual IR of culling of cows over time or any association between study design factors and the IR or incidence density of culling or mortality. These findings provide benchmarks for describing culling and mortality, and should encourage farmers and researchers in countries with modern dairy industries to discover and implement management strategies to reduce the animal welfare and economic costs associated with these changes.

Wooden hutch space allowance influences male Holstein calf health, performance, daily lying time, and respiratory immunity

Dairy calves in the western United States are commonly raised individually in wooden hutches with a space allowance of 1.23m(2)/calf. Recent legislative initiatives in California and across the United States were passed regarding concern over space allowance for farm animals. The objective of this study was to determine if rearing male Holstein calves in wooden hutches modified to increase space allowance would influence measures of performance, lying time per day, health, and respiratory immunocompetence. At 4d of age, 60 calves were randomly assigned to 1 of 3housing treatments: (1) conventional housing (CONV; 1.23m(2)/calf), (2) 1.5 × CONV (MOD; 1.85m(2)/calf), or (3) 3 × CONV (MAX; 3.71m(2)/calf). Intakes of milk and solid feed were recorded daily and body weight was measured at 0, 3, 6, 10, and 12 wk of age. For the first 3 wk of the trial, calves were scored daily for fecal consistency, hydration, and hide cleanliness. In addition, calves were scored for respiratory health (i.e., nasal and eye discharge, ear position) until 7 wk of age. The total lying duration per day was recorded using data loggers at 3, 6, and 10 wk of age. Eight clinically healthy calves from each treatment were sensitized with subcutaneous ovalbumin (OVA) and then challenged with aerosolized OVA to assess calf respiratory immunity at 11 wk of age. Bronchoalveolar lavage fluid (BALF) was collected 4d after the OVA challenge and analyzed for leukocyte differentials and OVA-specific IgG, IgG1, IgA, and IgE. Calf average daily gain and body weight were positively associated with space allowance at approximately 3 wk before weaning and throughout postweaning, respectively. A greater space allowance decreased lying time after 46d. Space allowance did not influence fecal consistency, but there was a tendency for MAX calves to take 1d longer to recover from loose feces than MOD calves. The MAX calves had the fewest (%) observations with feces on their body compared with CONV or MOD. At 3 wk of age, peripheral eosinophil concentrations decreased with increased space allowance. However, observations (%) of eye discharge increased with greater space allowance. Among calves challenged with OVA, MOD calves had the least BALF OVA-IgE, and the percent of BALF eosinophils decreased with increased space allowance. Increased space allowance for calves raised in wooden hutches may improve some measures of calf performance, health, and respiratory immunocompetence.

Invited review: Influence of climatic conditions on the development, performance, and health of calves

The objective of this review is to provide the reader with an overview of thermoregulatory mechanisms and the influence of climatic conditions in different housing systems on the development, performance, and health of calves. Thermic stress is observed in association with extreme temperatures and large temperature variations, but other variables such as relative humidity and wind speed can also contribute to thermic stress. Thermoregulation in calves is similar to that in adult cattle, but especially dystocial calves are more prone to heat loss. Heat or cold stress results in direct economic losses because of increased calf mortality and morbidity, as well as indirect costs caused by reduced weight gain, performance, and long-term survival. The climatic conditions in a variety of housing systems, associated health problems, and strategies to mitigate thermic stress are discussed in this review. The goal of housing is to alleviate the effect of climate on calves and provide a microclimate. Adequate ventilation with fresh air is essential to reduce respiratory disease. Common practices such as raising calves in individual outdoor enclosures have been challenged lately. Recent research seeks to evaluate the suitability of group housing under practical, economic, and animal welfare considerations. Limited results for reducing thermic stress can be achieved by simple measures such as shades or shelter, but additional heat or cold stress relieving strategies can be required depending on the housing system.

Invited review: Effects of group housing of dairy calves on behavior, cognition, performance, and health

Standard practice in the dairy industry is to separate the calf and dam immediately after birth and raise calves in individual pens during the milk-feeding period. In nature and in extensive beef systems, the young calf lives in a complex social environment. Social isolation during infancy has been associated with negative effects, including abnormal behavior and developmental problems, in a range of species. Here, we review empirical work on the social development of calves and the effects of social isolation in calves and other species; this evidence indicates that calves reared in isolation have deficient social skills, difficulties in coping with novel situations, as well as specific cognitive deficits. We also review the practices associated with group housing of dairy calves, and discuss problems and suggested solutions, especially related to cross-sucking, competition, aggression, and disease. The studies reviewed indicate that social housing improves solid feed intakes and calf weight gains before and after calves are weaned from milk to solid feed. Evidence regarding the effects of social housing on calf health is mixed, with some studies showing increased risk of disease and other studies showing no difference or even improved health outcomes for grouped calves. We conclude that there is strong and consistent evidence of behavioral and developmental harm associated with individual housing in dairy calves, that social housing improves intakes and weight gains, and that health risks associated with grouping can be mitigated with appropriate management.