Effects of milk replacer powder added to pasteurized whole milk over different durations on dairy calves fed ground starter diet with alfalfa hay

Adding milk replacer powder (MRP) to whole milk during the entire preweaning period can increase growth but raises concern because of low starter feed intake and slumps in average daily gain (ADG) at weaning and postweaning. In the current study, effects of adding MRP to pasteurized whole milk (PWM) during d 10-41 or d 10-59 of age were investigated in comparison with PWM. Calves [24 females and 21 males; 39.8 ± 1.85 kg body weight (BW)] were randomly allocated to 1 of 3 treatments: 1) conventional protocol, 5 L/d PWM from d 3-56, and 2.5 L/d from d 57-59 of age (CONV; TS intake = 31.9 kg), 2) short duration of adding MRP to PWM protocol, 5 L/d PWM from d 3-9, 5 L/d PWM + MRP (18% TS) from d 10-41, 5 L/d PWM from d 42-56, and 2.5 L/d PWM from d 57-59 (SD; TS intake = 42.3 kg), 3) long duration of adding MRP to PWM protocol, 5 L/d PWM from d 3-9, 5 L/d PWM + MRP from d 10-56, 2.5 L/d PWM + MRP form d 57-59 (LD; TS intake = 47.7 kg). The osmolality of PWM and PWM + MRP was 278 and 519 mOsm/L, respectively. Calves were weaned on d 60, and the study terminated on d 75. There was a treatment × time interaction for starter intake, where intake was greater for CONV than other treatments from d 14-41 and was greater in CONV than LD during d 42-48 and d 56-62 of age. Final BW was lower in CONV calves than LD calves. Weaning BW and overall hip height were lower in CONV calves than other treatments. The CONV calves had lower ADG at d 14-27 and 35-41 and SD calves had lower ADG at d 42-48 than other treatments. Calves fed CONV treatment had lower ruminal acetate and greater propionate than SD calves during preweaning. Calves fed LD treatment had lower total volatile fatty acids and tended to have greater ruminal pH than other treatments. Calves fed CONV had greater neutrophils and neutrophils/lymphocytes ratio and lower lymphocytes than other treatments. Glucose concentration was greater for LD versus other treatments at d 56, and lower for SD versus other treatments at d 70 of study. Insulin concentration and homeostatic model assessment of insulin resistance index were greater in LD compared with other treatments during preweaning but were not different postweaning. Serum BHB was greater in CONV than other treatments. Albumin was greater for CONV versus other treatments at d 56, however, it was greater in LD-fed calves at d 70 of study. Results indicate that feeding a PWM + MRP to the calves during the entire preweaning period resulted in lower starter feed intake around weaning, but overall starter intake was similar with a greater final BW and fewer health related issues throughout the study. Shifting a PWM + MRP to the conventional whole milk at d 40 of age decreased the ADG of calves.

Fructo-oligosaccharides supplementation enhances the growth of nursing dairy calves while stimulating the persistence of Bifidobacterium and hindgut microbiome's maturation

The colonization and development of the gut microbiome in dairy calves play a crucial role in their overall health and future productivity. Despite the widely proposed benefits of inulin-related products on the host, there is insufficient information about how supplementing fructo-oligosaccharides (FOS) impacts the colonization and development of the gut microbiome in calves. In a randomized intervention trial involving newborn male Holstein dairy calves, we investigated the impact of FOS on the calf hindgut microbiome, short-chain fatty acids, growth performance, and the incidence of diarrhea. The daily administration of FOS exhibited a time-dependent increase in the average daily gain and the concentration of short-chain fatty acids. Concurrently, FOS delayed the natural decline of Bifidobacterium, promoting the maturation and stabilization of the hindgut microbiome. These findings not only contribute to a theoretical understanding of the judicious application of prebiotics but also hold significant practical implications for the design of early life dietary interventions in the rearing of dairy calves.

Milk replacer feeding once or twice a day did not change the ruminal metabolomic profile and the microbial diversity of dairy calves from birth to weaning

In commercial dairy production systems, feeding calves once a day could be an alternative to reduce labor expenses. Several studies comparing once (OAD) versus twice (TAD) a day milk feeding systems have not evidenced differences in calf growth, rumen development, blood parameters or health scores, but impact on ruminal microbiota remains to be investigated. The objective of this study was to determine the effects of OAD or TAD on the establishment of the ruminal microbiota and its metabolic activity. Sixteen male calves (45.9 ± 5.7 kg at birth) were involved in the trial from birth to weaning (63 d). After the colostrum phase, 2 feeding programs based on a milk replacer were tested and calves were allocated to these programs on d 5. To study the establishment of the bacterial community, ruminal fluid was obtained from each calf one hour after the morning meal at 7 (d 7), 35 (d 35) and 63 (d 63) days of age. The ruminal metabolome was evaluated at a 7 d interval from d 1 to d 63. Ruminal microbiota and metabolite profiles were characterized by 16 S rRNA gene sequencing- and by H-NMR spectroscopy, respectively. Our results showed that feeding milk replacer once or twice a day did not change the ruminal microbiota and metabolites of dairy calves from birth to weaning. Microbial data showed that diversity and richness increased with age, suggesting a shift from an heterogeneous and less diverse community after birth (d 7) to a more diverse but homogeneous community at 35 and 63 d. These findings suggest that feeding milk once a day can be successfully applied to a calf feeding system without compromising microbial establishment and functions.

The age at first consumption of forage in calves and its effect on growth and rumination in the short- and long-term

BACKGROUND

Previous investigations into the effect of dietary forage on calf performance have been inconsistent, and there is a paucity of information exploring the effect of age on the growth performance and rumination of calves. Eighty-four female Holstein calves (41.5 ± 4.2 kg) were enrolled at birth, a subset of the calves were fed calf starter only (CON, n = 21) while the rest (n = 63) were classified into three treatment groups: the early (EHAY, n = 26, 5.1 ± 0.8 d), the middle (MHAY, n = 21, 7.9 ± 0.8 d) and the late (LHAY, n = 16, 12.1 ± 1.4 d) hay consumers. The short-term effect of the age at first forage consumption (AFF) on calves' feed intake was monitored until d 84. In addition, the long-term effects of AFF on body weight, structural growth and rumination behavior were recorded until d 196. Rumen samples were collected on d 1, 7, 35, 84 and 196 to analyze the rumen fermentation, while fecal samples were collected from d 78 to 84 to estimate digestibility parameters.

RESULTS

Treatment had no effect on feed intake. While, the EHAY calves tended to have lower BW and ADG compared to LHAY and CON calves. Several total-tract apparent digestibility parameters and digestible nutrients intake were significantly lower in EHAY calves compared with CON and LHAY calves. Calves in the EHAY group tended to begin ruminating ealier, while CON calves were the latest (12.3 vs. 15.5 days of age). A treatment and time interaction was present for rumination time due to greater rumination in calves consuming hay compared to CON calves in week 10 to 12, the differences in rumination disappeared afterwards, no long-lasting significant differences in the rumination and rumen fermentation parameters were found between treatments.

CONCLUSIONS

In conclusion, this study showed that hay consumption earlier in life (in the first week, around 5 days of life) could negatively affect the growth of the calf in the short and long term. Compared to consuming hay from the second week (around 12 days of life) or feeding concentrate only without hay, starting to consume hay from the first week could compromise nutrient digestibility and digestible nutrient intake independent of developing rumination behaviour and rumen fermentation.

Effects of propolis extract on growth performance and health condition of dairy calves

The aim of this study was to evaluate the effect of propolis ethanol extract, on performance, fecal structure, and general health status of calves during the preweaning phase. For this purpose, 24 Simmental calves that were given colostrum for the first 3 days after birth were enrolled in the study. The study started when the calves were 4 days old and finished when they were 60 days old. These calves were divided into two groups as propolis and control groups according to their weight and gender. Both groups were given the same ration and housed in individual calf huts under the same environmental conditions. Differently from the control group, the calves in the propolis group were given 4 mL of propolis extract (300 mg/mL) with an oral feeding syringe for 56 days after morning feeding. The amounts of feed intake and fecal scores of the calves were recorded daily. Health scores, rectal body temperature, fecal pH, body weight, and body measurements were recorded weekly. For the determination of the counts of Lactobacillus spp. and Bifidobacterium spp., fecal samples were collected at the beginning and at the end of the study. The results indicated that oral administration of propolis had positive effects in terms of some performance parameters, the number of days with diarrhea, and fecal scores. In this study, it was concluded that propolis extract had the potential to positively affect the growth performance and health status of preweaning calves.

Bacterial Causes of Intestinal Disease in Dairy Calves: Acceptable Control Measures

Although diarrhea in dairy calves is common, it is not always due to bacteria. Escherichia coli, Salmonella, and Clostridium perfringens are the most commonly implicated bacteria, but an etiologic diagnosis should be sought before specific treatment is instituted. Nonspecific treatment such as fluid, electrolyte, and nutritional support should be accomplished while diagnostics are pending. Antimicrobials should not be a first-line therapy for calf diarrhea. Control measures are discussed.

Effects of replacing steam-flaked corn with shredded sugar beet pulp on feed sorting, behavior, blood metabolites, and growth performance of dairy calves

This experiment was conducted to investigate the effects of partial replacement of steam-flaked corn (SFC) with shredded sugar beet pulp (SBP) in the starter diet on selective intake (sorting), feeding and chewing behavior, blood biochemical parameters, and growth in newborn female Holstein dairy calves. A total of 48 calves (3 d old; 40.1 ± 0.84 kg body weight; mean ± SE) were randomly assigned to 1 of 2 feeding treatments containing 0 or 25% SBP (percentage of dry matter [DM]) in the starter diet. Calves were weaned on d 61 and remained in the study until d 81. Intake of starter feed and total intake of DM (milk DM + starter feed DM), crude protein, and neutral detergent fiber were increased (P < 0.05) by feeding SBP; however, intake of starch (P < 0.01) and total intake of ether extract (P = 0.03) were decreased with no apparent effect on total intake of ME. Average daily gain, feed efficiency, final weight, and skeletal growth also showed no significant changes. Circulating concentrations of glucose, total protein, and albumin were not affected by partial replacement of SBP with SFC; however, higher concentrations of blood urea-N (P = 0.01) and a lower albumin-to-globulin ratio (P = 0.03) were observed in SBP- vs. SFC-fed calves. Calves fed SBP sorted more for particles retained on the 4.75-mm sieve (P = 0.02) and against particles retained on the 0.6-mm sieve and bottom pan (P < 0.01). Intake of neutral detergent fibers and starch from particles retained on all sieve fractions was increased and decreased (P < 0.01), respectively, by replacing SFC with SBP. Replacement of SBP with SFC was associated with increased meal length and meal size and increased rumination frequency and length, but decreased intervals between rumination (P ≤ 0.01). Calves fed SBP spent more time eating, rumination, and standing and less time lying and non-nutritive oral behaviors (P < 0.01). In general, 25% replacement of SFC with SBP did not affect calf performance but increased time spent rumination and eating and decreased non-nutritive oral behaviors.

Can calf age be estimated using a combination of serum gamma-glutamyl transferase, total protein and immunoglobulin G?

Our aim was to test a novel method for estimating the age of young calves, using serum γ-glutamyl transferase (GGT) activity, total protein concentration and immunoglobulin G (IgG) concentration. Blood samples were taken from 59 dairy calves at 2, 4, 6, 8, 10, 12, and 14 days of age, and serum GGT activity, total protein concentration, and IgG concentration were measured. Bayesian regression models were used to estimate the association of GGT, total protein, and IgG, with calf age. A multivariate hierarchical regression model was then created, and the model's reliability in estimating the age of simulated subjects was assessed. The univariate models showed a strong within-calf relationship between age and GGT (conditional R² (cR²) = 0.93), and age and total protein (cR² = 0.75), while the relationship between calf age and IgG was less consistent (cR² = 0.63). There was a high degree of variation between calves for these parameters, particularly for the relationship between age and total protein (marginal R² (mR²) 0.02), and age and IgG (mR² 0.01); somewhat less between-calf variation was seen for GGT (mR² 0.30). For the final multivariate model, we tested the model reliability by simulating new subjects. The credible intervals for estimates of calf age generated from the model were wide, indicating poor reliability. We concluded that single measurements of serum GGT activity, total protein concentrations and IgG concentrations cannot be used to reliably estimate the age of young calves to within 1-2 days.

Cryptosporidium parvum subtypes from diarrheic dairy calves in Israel

Cryptosporidium are protozoan parasites with worldwide distribution, infecting a wide range of terrestrial and aquatic animals, as well as humans. Cryptosporidium parvum is the most important zoonotic species and is the primary cause of cryptosporidiosis in preweaned calves, a highly prevalent, economically important disease. Extensive subtyping of C. parvum from infected humans and animals has expanded current understanding of the parasites' epidemiology. Israel has a highly developed dairy sector with intensive, zero-grazing operations. While C. parvum has been found in dairy calves throughout the country, and subtype data from human patients have also been published, subtype data from animals, and in particular preweaned ruminants, are lacking. We carried out an initial study of Cryptosporidium species and subtypes from preweaned diarrheic calves. Cryptosporidium species were determined in 71 fecal samples from 43 different dairy farms using 18S rRNA PCR, and subtyping of C. parvum based on the 60-kDa glycoprotein (gp60) sequences was done on one sample per farm. C. parvum was the only species found, with eight different subtypes belonging to the zoonotic IIa and IId families. Subtype IIaA15G2R1 was the most prevalent and widespread, found in 50% of the farms over a wide geographical distribution. Our results confirm the presence of subtypes IIaA15G2R1 and IIdA20G1, which were previously found in human patients in Israel, also in Israeli calves. In addition, subtype IIaA12G1R1 is reported here for the first time in an animal. These findings demonstrate the value of monitoring C. parvum subtypes in animal samples, and suggest that the role of calves as well as other young ruminants in the transmission of zoonotic cryptosporidiosis in Israel should be further studied.

Effects of different planes of milk feeding and milk total solids concentration on growth, ruminal fermentation, health, and behavior of late weaned dairy calves during summer

Background

In recent years, there has been an increasing interest in using high quantities of milk or milk replacer (MR) in heat-stressed calves to alleviate the negative effects of high environmental temperatures on their performance. However, observations have indicated a decline in growth performance in the weaning and post-weaning period, which might be optimized with increasing total solids (TS) in milk and weaning age. This study aims to optimize the effects of higher quantities of milk on late weaned calves' performance by increasing TS concentration or delivery route in summer conditions.

Method

Forty-eight newborn Holstein calves were used in a 2 × 2 factorial arrangement with the factors of pre-weaning total plane of milk (PM) intake (low vs. high) and milk TS content (12% vs. 17%). The treatments were (1) low PM (LPM) intake with 12% TS (TS intake = 45.9 kg), (2) LPM intake with 17% TS (TS intake = 65.1 kg), (3) high PM (HPM) intake with 12% TS (TS intake = 63.7 kg); and (4) HPM intake with 17% TS (TS intake = 90.3 kg). Calves were weaned at d 83, and the study was terminated at d 103 of age. Performance data (every 10 day), skeletal growth (d 80 and 100), ruminal fermentation parameters (d 48 and 91), and behavioral measurements (d 69, 70, 93 and 94) were analyzed as repeated measurements with PROC MIXED of SAS 9.4 (SAS Institute Inc., Cary, NC).

Results

Calves receiving HPM consumed less PMR from d 44 to 83 of age, but they had higher ADG from d 24 to 53 of age compared to those fed LPM (PM × age, P < 0.001). In addition, calves receiving milk with 17% TS had lower PMR intake from d 14 to 83 of age, but greater ADG from d 34 to 53 compared to those receiving milk with 12% TS (TS × age, P < 0.001). Calves that received HPM had greater skeletal growth parameters compared to LPM-fed calves, with a similar effect evident for calves fed milk with 17% TS compared with those fed milk with 12% TS. Calves receiving milk with 17% TS had greater fecal scores and diarrhea occurrence than those fed milk with 12% TS in HPM, but not LPM.

Conclusions

Increasing PM and milk TS concentration improved growth in summer-exposed calves as demonstrated by increased pre-weaning ADG, pre- and post-weaning BW, and structural growth.

Detection and molecular characteristics of bovine rotavirus A in dairy calves in China

Background

Bovine group A rotavirus (BoRVA) is a major cause of severe gastroenteritis in newborn dairy calves. Only one study has investigated the G and P genotypes among dairy calves in a few regions of China, which were G6 and P[5]. Therefore, data on the prevalence and molecular characteristics of BoRVA in dairy calves in China remains limited.

Objectives

The purpose of this study was to investigate the prevalence and molecular characteristics of BoRVA in dairy calves in China.

Methods

269 dairy calves diarrheic samples from 23 farms in six provinces in China were collected to detect BoRVA using reverse transcription polymerase chain reaction.

Results

71% of samples were determined to be BoRVA-positive. Two G genotypes (G6, G10) and two P genotypes (P[1], P[5]) were identified, and G6P[1] BoRVA was the predominant strain. Moreover, the VP7 and VP4 gene sequences of these dairy calf BoRVA strains revealed abundant genetic diversity. Interestingly, eight out of 17 complete G6 VP7 sequences were clustered into G6 lineage VI and analysis showed the strains were closely related to Chinese yak BoRVA strains.

Conclusions

The results of this study show that BoRVA circulates widely among dairy calves in China, and the dominant genotype in circulation is G6P[1], first report on molecular characteristics of complete P[5] VP4 genes in chinese dairy calves. These results will help us to further understand the prevalence and genetic evolution of BoRVA among dairy calves in China and, thus, prevent the disease more effectively.

Longitudinal health outcomes for enteric pathogens in preweaned calves on Ohio dairy farms

Calf gastrointestinal disease remains one of the main causes of productivity and economic losses on dairy operations. The majority of pre-weaned calf mortality is attributed to diarrhea or other digestive problems. Five enteric pathogens are commonly associated with diarrhea in dairy calves, including bovine rotavirus, bovine coronavirus, Escherichia coli, Salmonella spp., and Cryptosporidium parvum. Pathogen-associated differences in health outcomes and case fatality rates have not been well-characterized. Additionally, updated prevalence estimates may reflect important changes in the epidemiology of the pathogens on dairy farms. For this cohort study, fecal samples were collected from 276 clinically ill calves across 5 central Ohio dairy farms on the first day of diarrheal diagnosis. Genomic techniques, including reverse transcription polymerase chain reaction (RT-PCR) and droplet digital polymerase chain reaction (ddPCR) were used to test for the presence of the five enteric pathogens. A Poisson regression model was used to estimate the relative risk of mortality, and a survival analysis with a Cox regression model was used to analyze time to return to a healthy clinical status by pathogen. Rotavirus was the most frequently identified at 68.1 % (188/276), followed by F5 (K99)⁺E. coli at 42.5 % (114/268), C. parvum at 28.4 % (66/232), coronavirus at 5.8 % (16/276), and Salmonella had the lowest prevalence at 3.7 % (10/268). Risk of mortality tended to be higher for calves infected with Salmonella (RR = 3.83; 95 %CI: 0.93, 16.02, p = 0.062); however, the time to return to a healthy clinical status was not different for different pathogens. Only farm was a significant predictor of time to return to health (p = 0.017); the within-farm median duration of signs substantially varied between 2 and 7 days. The results suggest that the prevalence and distribution of rotaviral infections is higher than reported in prior studies. With the exception of infections caused by Salmonella spp., pathogen diagnosis on the first day of diarrhea was a poor predictor of the outcome and duration of disease. These results are critical to guide the implementation of prevention measures to detect, treat, and prevent calf diarrhea.

Influence of individual or group housing of newborn calves on rotavirus and coronavirus infection during the first 2 months of life

Bovine rotavirus A (RVA) and bovine coronavirus (CoV) are the two main viral enteropathogens associated with neonatal calf diarrhea. The aim of the present work was to study the impact of group and individual housing systems in the epidemiology of RVA and CoV infection. Eleven calves reared in individual housing (FA) and nine calves in group housing (FB) were monitored during the first 7 weeks of life. Stool and serum samples were screened for RVA and CoV antigens by ELISA. IgG1 antibodies (Ab) to both antigens were also measured. From the 160 fecal samples collected, the proportion of positive samples to RVA and CoV was significantly higher in FB (23.6%) than in FA (9%) (p = 0.03). The geometric mean of colostral IgG1 Ab titers to CoV and RVA in FA (IgG1 anti-CoV 1024 and anti-RVA 1782.9) was lower than in FB (IgG1 anti-CoV 10,321.2 and anti-RVA 4096) at birth. Calves less than 2 weeks of life from FB had a higher risk of being infected by RVA (OR = 4.9; p = 0.01) and CoV (OR = 17.15; p = 0.01) than calves from FA. The obtained results showed that there was higher RVA and CoV shedding in group-housed calves than in individual-housed animals.

Effects of wheat straw particle size as a free-choice provision on growth performance and feeding behaviors of dairy calves

In the dairy calf feeding, supplementation of forage to the starter feed is commonly practiced. However, data are insufficient about how changes in particle size (PS) of forage affect calf performance and behavior in a free-choice forage provision system. This study aimed to assess the effects of supplementing wheat straw varying in PS on performance, skeletal growth characteristics, ruminal pH, nutritional behaviors, and blood metabolites of dairy calves. Forty-eight Holstein calves (43.8 ± 3.2 kg of BW) from d 15 of age were randomly assigned to one of the four treatments (n = 12/treatment; six males and six females): (1) starter without wheat straw supplementation (CON), (2) CON supplemented with wheat straw chopped at 1 mm geometrical mean particle length (GMPL) (fine PS), (3) CON supplemented with wheat straw at 4 mm GMPL (medium PS), and (4) CON supplemented with wheat straw at 7 mm GMPL (long PS). The calves were given ad libitum access to feed and water throughout the study. All calves were weaned on d 56 of age and continued the experiment until d 90. The starter, wheat straw, and total solid feed intakes were not affected by GMPL of wheat straw; however, CON calves had a lower solid feed-, total DM- and NDF-intake than calves offered wheat straw. Further, ADG, weaning, and final BWs as well as feed efficiency were similar between treatments. No difference was observed in growth rate of hip height, hip width, body barrel, wither height, and heart girth among treatments, however, wheat straw supplemented calves tended to have greater body length at weaning. Blood concentration of serum β-hydroxy butyrate was greater in wheat straw supplemented calves compared with CON calves on d 56 and 90. Calves supplemented with wheat straw spent more time eating starter and forage, lying and ruminating and less time for standing and non-nutritional behaviors compared with the CON calves on d 49 and 63 of the study. Moreover, calves offered wheat straw had greater ruminal pH than CON calves at 4 and 8 h after offering starter feed on d 35. In conclusion, supplementing wheat straw as a free-choice increased solid feed intake, rumen pH, and calves' welfare, however, PS of wheat straw had no effect.

Physiological responses of Holstein calves to hot weather conditions

The objectives of the study described were to (1) compare environmental temperature-humidity index (THI) with the THI measured within two different calf housing systems and (2) determine how THI affects Holstein heifer calf body temperatures, serum cortisol concentrations, and serum thyroxine concentrations. At 24 to 48 h of age, calves were assigned to one of two individual housing treatments: (1) stalls in a three-sided barn (n = 8) or 2) hutches placed outside (n = 8). Calves were observed until 42 days of age during the summer months. Ambient temperature and relative humidity within housing systems were recorded hourly. Calf body temperatures were measured hourly using devices attached to the underside of each calf's tail. Blood samples were collected at 7, 21, and 42 days of age via jugular venipuncture. Blood serum was analyzed for cortisol and thyroxine concentrations using enzyme-linked immunosorbent assays (ELISAs). Overall average THI was higher in hutches than in stalls (P < 0.0001). Calves housed in hutches had higher body temperatures (39 ± 0.18 °C vs 38 ± 0.15 °C, P = 0.005). No differences occurred in serum cortisol concentrations (P = 0.89) but at 21 days of age, calves housed in hutches had higher serum thyroxine concentrations (16.55 ± 0.51 μg/dl vs 13.91 ± 0.54 μg/dl, P = 0.0006) than calves housed in stalls. Although both housing systems in this study were located on the same dairy, calves housed in hutches were exposed to higher THI values, had higher body temperatures, and at 21 days of age had higher serum thyroxine concentrations than calves housed in stalls inside a three-sided barn.

Effects of antimicrobial exposure on the antimicrobial resistance of Escherichia coli in the digestive flora of dairy calves

Veal calves are often identified as reservoirs for antimicrobial resistant Escherichia coli (E. coli). This production is closely linked with dairy production, as young calves - mostly males - are collected from dairy farms to enter the fattening process. The aim of this prospective study was to explore the factors on dairy farms that favour the selection of antimicrobial resistance (AMR) in the digestive E. coli strains of young calves and to assess whether the resistance levels and selection pressure were the same for males and females. The exposure of calves to antimicrobials was investigated through three factors: antimicrobial treatment of calves; feeding of calves with milk from cows treated with antimicrobials; and the consumption of colostrum from cows treated with antimicrobials at dry-off. The study design involved 100 dairy farms. A calf of each sex was selected from birth on each farm. Information on the calves' exposure to antimicrobials was collected daily and calves were sampled (rectal swab) two weeks after birth, then seven weeks after birth for females only. Laboratory analyses included culture on two distinct media: a non-selective medium (identifying dominant flora) and a medium containing ceftiofur to select the extended-spectrum beta-lactamase (ESBL) phenotype. Susceptibility testing was performed on an E. coli strain from each medium. Generalised linear models were used to assess associations between the resistance of E. coli strains and antimicrobial exposure. A set of 280 swabs from healthy calves were analysed. In dominant flora, high levels of resistance (>60 %) were identified for streptomycin, tetracycline and amoxicillin but AMR levels were low (3 %) for critically important antimicrobials (3^rd- and 4^th-generation cephalosporins and fluoroquinolones). For females staying in dairy farms, a marked decrease in resistance was observed for almost all antimicrobials between the age of 15 days and 7 weeks. A selective medium revealed an ESBL phenotype for 20.7 % of the calves. Whether for AMR or antimicrobial exposure, no significant difference was found between male and female calves. The antimicrobial treatment of calves was associated with an increased resistance of E. coli from dominant flora for amoxicillin (OR = 2.9), gentamicin (OR = 4.6), florfenicol (OR = 5.0) and trimethoprim-sulfonamide (OR = 5.6). The consumption by calves of milk from cows treated with antimicrobials was also associated with an increased resistance to amoxicillin (OR = 2.6), gentamicin (OR = 4.0), tetracycline (2.6) and trimethoprim-sulfonamide (OR = 2.2). In contrast, the models did not reveal any association between AMR and consumption of colostrum from cows treated with antimicrobials at dry-off.

Epidemiological study on calf diarrhea and coccidiosis in dairy farms in Bahir Dar, North West Ethiopia

Background

A longitudinal prospective study was conducted from October 2017 to April 2018 on calf diarrhea and coccidiosis in dairy farms in Bahir Dar, North West Ethiopia with the objectives of determining the incidence of calf diarrhea and calf coccidiosis from diarrheic calves, assessing the major risk factors associated with calf diarrhea and coccidiosis and identifying the existing Eimeria species. A total of 237 calves, 86 calves from 52 smallholder dairy farms and 151 calves from 8 large dairy farms, were used for this study. Fresh fecal samples were collected from 86 diarrheic calves for identification of Eimeria species.

Results

Overall incidences of calf diarrhea and coccidiosis found in this study were 33.5 and 20.1%, respectively. In total, 19 potential risk factors were investigated for their association with calf diarrhea and coccidiosis from diarrheic calves using Cox regression. Age of calf (HR = 2.057, P = .002), body condition (HR = 1.802, P < .001), house condition (HR = 2.072, P = .004) and age at first colostrum feeding time (HR = 2.107, P = .002) were found significantly (P < 0.05) associated with the risk of diarrhea by multivariate Cox regression. Among the risk factors tested, age (HR = 13.36, P < .001) and sex of calves (HR = 3.500, P = .020) were found significantly (P < 0.05) associated with coccidiosis by multivariate Cox regression. A total of nine Eimeria species were identified. E. bovis (28.6%), E. zuernii (19.0%) and E. auburnensis (14.3%) were the most common Eimeria species encountered.

Conclusion

The incidence of calf diarrhea and coccidiosis was high in the dairy herds in North West Ethiopia. Therefore, sound dairy calf management practices are needed to mitigate risk factors for calf diarrhea and coccidiosis with a view to reducing the incidence of calf diarrhea and coccidiosis in Ethiopian dairy farms.

Short communication: Are group size and pasteurization of whole milk associated with diarrhea and growth of pre-weaned organic dairy calves?

The objective of our study was to assess effects of pasteurization of milk and group size on the prevalence of diarrhea and daily growth in organic pre-weaned calves. Our study was conducted in six organic dairy herds where 353 pre-weaned calves were randomly placed in groups of two or four calves from one week of age. Three herds used pasteurized milk in a first five-month period and un-pasteurized milk in a second five-month period and three herds used unpasteurized in the first and pasteurized in the second period. The number of colony forming units (CFU)/mL was measured from samples of pasteurized and un-pasteurized milk fed to the calves. Diarrhea was measured as fecal smear under and/or at the tail and hind legs and as liquid feces. Heart girth growth was estimated using inflexible measuring tape. Group size and pasteurization were not significantly associated with either diarrhea or daily growth.

Supplementation of Cr Methionine During Dry Period of Dairy Cows and Its Effect on Some Production and Biochemical Parameters During Early Lactation and on Immunity of Their Offspring

This study aimed to investigate the effect of dietary chromium methionine (Cr-Met) supplementation on the production and immunological parameters of dairy cows during the dry and postpartum period and their offspring. Forty-five Holstein transition cows were randomly assigned to experimental groups with control, positive control (levamisole-injected cows), and treatment groups (5 g dietary Cr-Met/day/cow). Production, immunological, and biochemical parameters were analyzed during the dry and postpartum period. Result revealed that in dry cows, monocyte count and serum glucose level significantly (p < 0.05) decrease in Cr-supplemented cows over control. Similarly, after parturition, the numbers of all immune cells (except monocytes) decreased significantly (p < 0.05); however, serum IgG, ALT, AST, glucose levels, and total leucocyte, neutrophil, and leucocyte count were increased significantly (p < 0.05) in Cr-supplemented cows over the control group. Days in milk (DIM) of treatment cows were significantly (p < 0.05) decreased over the control group; however, no significant (p > 0.05) differences were observed on milk production, colostrum, and IgG concentrations. As a conclusion, the supplementation of Cr had positive effects on immune cells of cows after parturition; however, serum biochemical parameters remained unaffected. Also, there were significant differences on the number of total leucocyte and neutrophil, on the activity of ALT at birthday, and on the number of total leucocyte at postpartum for calves.

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.

Mortality, diarrhea and respiratory disease in Danish dairy heifer calves: Effect of production system and season

Diarrhea and respiratory disease are major health problems for dairy calves, often causing calf mortality. Previous studies have found calf mortality to be higher in organic dairy herds compared to conventional herds. The aim of this study was to investigate the association between production system (conventional/organic), season (summer/winter) and calf mortality risk, diarrhea, signs of respiratory disease and ocular discharge, respectively, for dairy heifer calves aged 0-180 days. Sixty Danish dairy herds, 30 conventional and 30 organic, were visited once during summer and once during winter. During the herd visits, calves were clinically examined for signs of diarrhea, hampered respiration, nasal discharge, coughing and ocular discharge. Data on mortality were obtained from the Danish Cattle Database. Data were analyzed using logistic regression models, with mortality risk and disease measures as outcome variables for each of three calf age groups: 0-28, 29-90 and 91-180 days. In organic herds, odds of mortality among calves aged 0-28 days were 2.09 (95% confidence interval (CI): 1.38-3.15) times higher during winter compared to summer. Odds of nasal discharge for calves 0-28 days in organic herds were 10.3 (95% CI: 2.27-46.6), 10.7 (95% CI: 2.40-40.0) and 5.97 (95% CI: 1.29-27.6) times higher for organic and conventional herds during winter (OW and CW) and conventional herds during summer (CS) respectively, compared to organic herds during summer (OS). For calves aged 29-90 days, odds of nasal discharge were 8.22 (95% CI: 3.88-17.4), 8.06 (95% CI: 3.18-20.4) and 2.86 (95% CI: 1.08-7.55) times higher for OW, CW and CS respectively, compared to OS. Odds of nasal discharge for calved aged 91-180 days were 7.03 (95% CI: 3.95-12.5) and 4.27 (95% CI: 1.81-10.1) times higher for OW and CW respectively compared to OS. For calves aged 29-90 days, odds of coughing were 2.23 (95% CI: 1.06-4.71) and 3.82 (95% CI: 1.76-8.21) times higher for OW and CW compared to OS, while odds of coughing for calves aged 91-180 days were 2.09 (95% CI: 1.19-3.67) and 2.55 (95% CI: 1.39.4.67) times higher for OW and CW compared to OS. Odds of ocular discharge for calves aged 29-90 days were 0.22 (95% CI: 0.10-0.52), 0.27 (95% CI: 0.11-0.66) and 0.42 (95% CI: 0.18-0.99) times higher for OW, CW and CS compared to OS. In conclusion, mortality and morbidity of Danish dairy heifer calves are, for some variables and in certain age groups, dependent on production system and season.

Quantification of antimicrobial usage in dairy cows and preweaned calves in Argentina

Antimicrobials are commonly used to treat diseases in dairy cows and in calves. In Argentina information about veterinary antimicrobial usage at herd level is still limited. The purpose of this study was to quantify antimicrobial usage at herd level of most used drugs to treat lactating cows (LC) and preweaned calves (PWC). Prevalence of diseases and antimicrobial drug usage in 18 milking herds and in 11 calves rearing units (CRUs) were assessed through a survey. Drug usage (DU) at herd level was estimated through a standardized indicator, the number of Defined Daily Doses Animal (DDDA) per year, considering a standardized body weight of 600kg for LC and of 60kg for PWC. Pearson correlation coefficients were estimated and used to evaluate the association of LC herd size and milk yield (kg/day) with each disease prevalence and with DU. Student t-Test was used to compare disease prevalence and DU with various management practices in CRUs. Clinical mastitis was the most prevalent disease followed by foot, uterine and respiratory diseases in adult dairy cows. More involvement of veterinarians in treatment decisions was observed in larger dairy herds. Most used antimicrobials were beta-lactams and aminoglycosides. Especially for intramammary compounds, there was a trend towards multidrug formulations. The median DU was 5.21 DDDA/LC/year (range=2.88-10.88), the intramammary usage for clinical mastitis (IM-CM) and dry cow therapy (IM-DRY), representing 85.4% of total drug usage. No significant correlations were observed between herd size or milk yield with disease prevalence and with DU for all considered uses (IM-CM, IM-DRY and parental (PAR)). Enteritis was reported in all CRUs, followed by respiratory disease (91%), and omphalophlebitis (3%). The median DU for all drugs used at CRU level was 0.49 DDDA/PWC/year. Prevalences and DU for treatment of enteritis and respiratory diseases did not differ significantly between rearing systems, colostrum management or permanence time of the calf with the mother after birth. Although it was possible to estimate the drug usage at farm level, it was observed that the diversity of drug compounds and dose heterogeneity presented by the various manufacturers made the calculation of those indicators complex.

Evaluation of a protocol to reduce the incidence of neonatal calf diarrhoea on dairy herds

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Dams were vaccinated against E. coli, rota and corona, calves received halofuginone.

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The average % of neonatal calf diarrhoea was significantly lower on trial herds.

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The average shedding of C. parvum was significantly lower on trial herds.

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No significant differences were observed in the shedding of E. coli, rota and corona.

Calf diarrhoea causes substantial economic losses in cattle herds worldwide. Neonatal calves are particularly sensitive to infections with enteropathogens. The present study focused on prevention against the main infectious causes of neonatal calf diarrhoea i.e. Escherichia coli, rota- and coronavirus, and Cryptosporidium parvum. Dairy herds (n = 24) with a high percentage of neonatal calves scouring (>10%) were included and calves were sampled for the presence of these four enteropathogens. To decrease diarrhoea problems among neonatal calves, a standard protocol was tested on 13 herds (treatment group) where both C. parvum and either E. coli or rota- or coronavirus were identified as being involved, the other 11 herds served as control group. The protocol consisted of 2 points of action: preventive vaccination of dams against E. coli, rota- and coronavirus, and preventive administration of halofuginone lactate to newborn calves. The average percentage of calves suffering from neonatal diarrhoea (39.7% versus 14.3%, P < 0.01) and the average percentage of faecal samples positive for C. parvum (34% versus 11%, P < 0.05) differed significantly between control herds and treatment herds after implementation of the protocol. No significant differences between control and treatment group were observed in the percentage of calves excreting E. coli, rotavirus and coronavirus, both before and at the end of the trial. Furthermore, risk factors potentially associated with the development of neonatal calf scours were determined. Non-significant results were obtained for the effect of the protocol on duration of diarrhoea and the effect of the colostral IgG quantity on the risk of diarrhoea. Passive immunity transfer status of the calves, measured both before the onset and at the end of the study, were non-significant between groups.

Amelioration of salmonellosis in pre-weaned dairy calves fed Saccharomyces cerevisiae fermentation products in feed and milk replacer

Salmonellosis is an insidious and potentially epidemic problem in pre-weaned dairy calves. Managing this disease, or any other diarrheal disease, is a financial burden to producers. Calf mortalities and medicinal treatments are overt costs of salmonellosis, while hidden costs include hampered weight gains and persistent intestinal colonization of the pathogen. In this study, we examined the anti-Salmonella effects of Saccharomyces cerevisiae fermentation products (SCFP) incorporated into both the milk replacer and the starter grain. In a blinded study, 2-8 day-old calves were fed SCFP (n=20 calves) or an SCFP-free Control (n=20 calves) for two weeks before and three weeks after experimental challenge with Salmonella enterica serotype Typhimurium. Following the challenge, calves were monitored for clinical signs and parameters associated with salmonellosis. Calves were then euthanized and examined for rumen development and intestinal Salmonella colonization. When compared to calves that received milk replacer and feed lacking SCFP, calves fed SCFP had fewer bouts of diarrhea and fever. Rumens from these calves were more developed, as measured by the length of papillae, which is consistent with the enhanced weight gain observed in this treatment group. Additionally, Salmonella intestinal colonization was reduced in SCFP-fed calves and Salmonella fecal shedding disappeared at an earlier stage in these calves. This study revealed that the combination of two proprietary S. cerevisiae fermentation products provide marked benefit for preventing the negative effects of salmonellosis in pre-weaned dairy calves, while also boosting productivity. The mechanism of action needs to be clarified, but it may be related to the observed decrease in colonization by the pathogen and increase in rumen development.

Factors associated with morbidity, mortality, and growth of dairy heifer calves up to 3 months of age

Calfhood disease is an important problem on many dairy operations that can have substantial effects on heifer survival and productivity, and has economic and welfare impacts. Neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) are the most common causes of morbidity and mortality in young dairy cattle. The objective of this observational study was to investigate factors associated with the risks of morbidity and mortality, and with growth, in commercial dairy heifers calves. A total of 2874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1-7 days of age and followed for approximately 3 months. Using cut-points of serum total protein of 5.2 and 5.7 g/dl, the incidences of failure of transfer of passive immunity (FTPI) were 11 and 32%, respectively. A cut-point of 5.7 g/dl was the most predictive of BRD before 5 weeks of age (sensitivity=40%, specificity=69%). The positive predictive value was poor (PPV=18%), but the negative predictive value was good (NPV=87%). A cut-point of 5.2g/dl was most predictive of death before 5 weeks of age (sensitivity=27%, specificity=89%, PPV=5%, NPV=98%). Serum total protein during the first week of life was a poor predictor of NCD. Over 23% of calves were treated for diarrhea. Risk factors were weight at enrollment, other diseases before 2 weeks of age, and an interaction between season of birth and herd-level incidence of NCD. Almost 22% of calves were treated at least once for BRD. Factors associated with an increased risk of BRD included herd-level incidence of BRD, season of birth, navel dipping, other diseases before 2 weeks of age, failure of transfer of passive immunity, and manual control of temperature in pre-weaning housing. Administration of supplemental antibody products at birth was associated with a reduced incidence of BRD. Overall mortality was 3.5%. Risk of mortality was increased by treatment for BRD and other diseases. The mean average weight gain was 0.95 kg/day (range: 0.11-1.62 kg/day; SD=0.2). Twinning status, FTP, treatment for NCD or other diseases, and month of birth influenced body weight. This study illustrated relationships among various diseases, mortality, and growth. Furthermore, it demonstrated the importance of colostrum for protection against BRD and improved growth performance, while bringing into question the optimal method of determining failure of transfer of passive immunity.