INVITED REVIEW: Phenotyping strategies and genetic background of dairy cattle behavior in intensive production systems - from trait definition to genomic selection

Understanding and assessing dairy cattle behavior is critical for developing sustainable breeding programs and management practices. The behavior of individual animals can provide valuable information on their health and welfare status, improve reproductive management, and predict efficiency traits such as feed efficiency and milking efficiency. Routine genetic evaluations of animal behavior traits can contribute to optimizing breeding and management strategies for dairy cattle but require the identification of traits that capture the most important biological processes involved in behavioral responses. These traits should be heritable, repeatable, and measured in non-invasive and cost-effective ways in many individuals from the breeding populations or related reference populations. While behavior traits are heritable in dairy cattle populations, they are highly polygenic, with no known major genes influencing their phenotypic expression. Genetically selecting dairy cattle based on their behavior can be advantageous because of their relationship with other key traits such as animal health, welfare, and productive efficiency, as well as animal and handlers' safety. Trait definition and longitudinal data collection are still key challenges for breeding for behavioral responses in dairy cattle. However, the more recent developments and adoption of precision technologies in dairy farms provide avenues for more objective phenotyping and genetic selection of behavior traits. Furthermore, there is still a need to standardize phenotyping protocols for existing traits and develop guidelines for recording novel behavioral traits and integrating multiple data sources. This review gives an overview of the most common indicators of dairy cattle behavior, summarizes the main methods used for analyzing animal behavior in commercial settings, describes the genetic and genomic background of previously defined behavioral traits, and discusses strategies for breeding and improving behavior traits coupled with future opportunities for genetic selection for improved behavioral responses.

Association between a pyroelectric infrared sensor monitoring system and a 3-dimensional accelerometer to assess movement in preweaning dairy calves

The objective of this study was to correlate movement assessed by a pyroelectric infrared sensor system in preweaning dairy calves with lying and standing time assessed by a 3D accelerometer considering the temperature-humidity index (THI). A total of 35 dairy calves (1-7 d of age) were enrolled in the study and 20 calves were included in the final analyses. The lying and standing time of the calves was monitored with a 3D accelerometer (Hobo Pendant G Data Logger, Onset Computer Corporation, USA), which was used as the gold standard reference. The infrared sensor monitoring system (IMS; Calf Monitoring System, Futuro Farming GmbH, Germany) was fixed to the fence of the calf hutch within the calf's reach. Temperature-humidity was monitored with 2 validated THI sensors inside and on outside of each calf hutch. Additionally, one THI sensor was located near the calf hutches. The observation period lasted 14 consecutive days. The average standing time assessed by the 3D accelerometer was 13.4 ± 12.7 (mean ± standard deviation) min/h and the average lying time was 46.6 (±12.7) min/h. The median (25th percentile; 75th percentile) number of movements measured by the IMS was 360 (60; 919) movements per hour. Number of movements per hour measured by the IMS was compared with data obtained with a validated 3D accelerometer. The Pearson correlation coefficient between both standing and lying time and the number of movements was r = 0.85 and r = -0.85, respectively. The Pearson correlation coefficients were only slightly influenced by THI (low THI [<68]: r = 0.86; medium THI [68-72]: r = 0.85; high THI [>72]: r = 0.81). Our data show that the number of movements of dairy calves measured by IMS were highly correlated with the chosen gold standard reference method. High THI slightly affects the measurement accuracy of IMS.

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.

Providing long hay in a novel pipe feeder or a bucket reduces abnormal oral behaviors in milk-fed dairy calves

Many milk-fed dairy calves are not provided forage. In these settings, calves often perform abnormal repetitive behaviors (ARBs), including tongue rolling and nonnutritive oral manipulation (NNOM), which, based on their form, seem similar to movements used when processing feed. Feeding hay, typically presented as a short chop (≤5 cm) in a bucket, reduces ARBs. Our objective was to evaluate whether altering the presentation method of long hay (∼19 cm), by providing it in a bucket or a novel polyvinyl chloride (PVC) pipe feeder, could reduce ARBs. Holstein heifer calves were housed individually on sand and fed ad libitum starter grain and limited milk replacer (5.7-8.4 L/d step-up) via a bottle (Control, n = 9) or given access to mountaingrass hay in a bucket (Bucket, n = 9) or in a PVC pipe feeder (Pipe, n = 9). The 56 × 10.2 cm (length × diameter) PVC pipe feeder had 4 openings that were 6.35 cm wide, which required the calf to insert her tongue into the pipe and curl her tongue to extract hay. Treatments were applied from birth through 50 d of age, when step-down weaning began and TMR was provided to all calves. Calves were fully weaned at d 60. At wk 4 and 6, oral behaviors (eating, ruminating, drinking water, sucking milk, self-grooming, NNOM, tongue rolling, tongue flicking, and panting) were recorded by direct observation for 24 h using 1-0 sampling during 5-s intervals. Feeding long hay, regardless of presentation method, increased overall DMI, grain intake, and ADG compared with Control calves. Hay provision also increased rumination (25 vs. 15% of 24-h observations in Control) and eating time (5.5 vs. 2% in Control). Abnormal behaviors were seen in all calves. Hay provision reduced some of these, including NNOM (5 vs. 9% in Control). There was no difference in NNOM between calves fed hay in a pipe or bucket, even though Bucket calves consumed more hay (178 vs. 129 g/d in wk 6) and tended to spend more observations eating hay than Pipe calves (4.5 vs. 3%). Hay provision did not affect other behaviors: drinking water (0.5%), grooming (3%), or tongue flicking (3%). We also found evidence of other abnormal oral behaviors that have received less attention. Calves showed signs of polydipsia, and displayed excessive grooming, the latter indicated by overall duration, number of bouts per day, and duration of individual bouts (up to 25 min). Tongue rolling was expressed at low levels (up to 0.4% of intervals) but by 85% of calves. Feeding hay, both in a bucket and using novel methods, was not enough to counteract the welfare challenges associated with individual housing and limited ability to suck milk (<1% of time). Provision of long hay, regardless of presentation method, promotes rumination, improves performance (higher grain intake and ADG) and reduces at least some, but not all, of the considerable abnormal oral behaviors these calves performed.

Evaluation of different liquid diets associated with environmental enrichment in the performance and behaviour of dairy calves

This study aimed to evaluate the effect of two liquid diets and the use of environmental enrichment (EE) in individually housed calves fed in open buckets. The treatments were arranged in a 2 × 2 factorial design, with factor 1 as the liquid diets: Whole Milk (WM) or Milk Replacer (MR); and factor 2 as absence or presence of environmental enrichment (brushes and a dry teat). Twenty-four newborn Holstein calves were distributed in four treatments: (1) WM; (2) WM + EE; (3) MR; and (4) MR + EE. Calves had free access to water and calf starter concentrate and were fed in a step-up/step-down feeding program and were weaned at 56 days of age. There was no effect of the association of different liquid diets with EE on the performance of the animals. The association of liquid diet with EE did not affect metabolic parameters, but WM-fed calves had higher concentrations of β-hydroxybutyrate (P < 0.05). Likewise, the interaction of liquid diet and EE did not affect the faecal score (P > 0.05), but animals fed with MR had more fluid faeces (P < 0.05). There was no change in the animals' behavioural repertoire as a function of liquid diets associated with EE. The animals used the EE approximately 1.4% of the time only and vocalized for 1.7% or performed non-nutritive feeding for 1.9%. There was a tendency (P < 0.06) for a reduction in vocalization by EE availability. However, the possibility of improved animal welfare using environmental enrichment is not ruled out since the animals vocalized less during the weaning process.

Impact of Stationary Brush Quantity on Brush Use in Group-Housed Dairy Heifers

Our objectives were to evaluate the effect of stationary brush quantity on brush use and competition in weaned dairy heifers naïve to brushes. Sixty-three Holstein heifers (95 ± 5.7 days old) were housed in groups of eight (with the exception of 1 group of 7) with two or four stationary brushes (n = 4 groups/treatment). Brush-directed behaviors of grooming, oral manipulation, and displacements were recorded continuously for all heifers 0–6, 18–24, 120–126 and 138–144 h after brush exposure. Linear mixed models were used to evaluate the effects of brush quantity and exposure duration. Total brush use and competition were not affected by brush quantity, but heifers with access to more brushes used them for longer bouts, suggesting greater opportunity for uninterrupted use. Total brush use was greater in the first and final 6 h observation periods, which was driven by the greatest duration of oral manipulation and grooming in those respective periods. The continued use of brushes by all heifers in the final period indicates the importance of providing appropriate outlets for these natural behaviors to promote animal welfare. The effect of brush quantity on bout characteristics suggests that brush use was less restricted with four compared to two brushes per eight heifers.

A review of factors affecting the welfare of dairy calves in pasture-based production systems

Current research on factors affecting the welfare of dairy calves is predominantly based on indoor, year-round calving systems. Calf rearing in these systems differs from that in more seasonal, pasture-based dairy production, meaning that risks to the welfare of dairy calves may not always be comparable between the two systems. The aim of this review was to consolidate the scientific literature relating to calf welfare in pasture-based dairy systems from birth until weaning, allowing for (1) the identification of current and emerging risks to calf welfare and (2) the formation of recommendations to mitigate these risks. Many of the risks to calf welfare discussed in this review are not exclusive to pasture-based dairies. This includes a global trend for increasing perinatal mortalities, a significant number of calves failing to achieve effective passive transfer of immunity, the low uptake of best practice pain relief when calves are disbudded, and the feeding of restricted milk volumes. In addition to these persisting welfare risks, two factors discussed in this review pose an immediate threat to the social license of dairy farming; the separation of cow and calf soon after birth and the management of surplus calves (i.e. calves not needed by the dairy industry). Several recommendations are made to improve the uptake of best-practice calf rearing and progress the development of alternative pasture-based rearing systems that accommodate changing community expectations. These include communication strategies that strengthen farmer beliefs regarding the welfare and productivity benefits achieved by best practice calf rearing and challenge beliefs regarding the associated costs. Farmers should also be encouraged to benchmark their rearing practices through improved record keeping of key rearing inputs and outcomes. Biological research is needed to advise the development of new calf rearing recommendations and the evolution of existing recommendations. Research priorities identified by this review include the effects of dystocia on the neonate and strategies to mitigate these effects, relationships between features of pen design and calf health and welfare, feasibility of dam rearing in large pasture-based dairy systems, and strategies that increase the value of the surplus calf.

Preweaning dairy calves' preferences for outdoor access

Adult dairy cattle show a preference for outdoor spaces during summer nights, but little is known about such preferences for dairy calves. Our aim was to determine the preferences of dairy calves for outdoor access during their first 11 wk of age in summer conditions. Calves were paired (n = 10) at 7 d of age and placed in one of 10 pens (7.32 × 2.44 m, deep bedded with bark mulch), each with equally sized outdoor and indoor areas. All feed was provided indoors; calves had ad libitum access to water, hay and concentrate. During the preweaning period, from 5 to 29 d of age, calves were offered 12 L/d of milk divided into 2 feedings. Calves were weaned stepwise, with milk gradually reduced by 1 L/d from d 30 to 35 of age. Calves were fed 6 L/d from 35 to 51 d of age, then milk was again reduced by 1 L/d so that calves were completely weaned by 56 d of age. Calves remained in the trial until, on average (± SD), 72 ± 2 d of age. Pens were continuously video recorded, and behaviors were scored 3 d/wk using 5-min scan samples. Four observers scored whether calves were inside, outside, lying, standing, in the sun or shade (interobserver reliability = 0.97). Sun and shade could not always be detected, so a proportion was calculated as the amount of time in the sun or shade divided by the total time sun or shade was visible. Calves spent approximately one-third of their time outside throughout the experiment, and time spent outside was affected by several factors. Pairs of calves spent less time outside as the amount of rain increased. During the first 6 wk of age, time spent outside increased, but time spent outside decreased between wk 6 and 7, and remained around 200 min/d from wk 7 to 11. Calves with the highest average daily gain and calves that were approximately 50% white appeared to spend more time outdoors. When outside, calves spent similar amounts of time in the sun and shade during the first 8 wk, but after weaning they appeared to spend more time in the shade. When calves were outside they appeared to spend a greater proportion of their time standing than when they were indoors during the first 4 wk. These results indicate that, when given the option in the summer, calves make use of an outdoor space, but this appears to vary with weather, calf age, average daily gain, and coat color.

Strategies to encourage freestall use in dairy heifers

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Transitioning to freestalls can be challenging for heifers.

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We evaluated the effects of social models and brushes on freestall use. No treatment effects were detected.

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Lying behavior improved with days of exposure to freestalls.

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Some abnormal behavior (lying in alley, lying backward in stall) persisted.

Dairy cattle can experience problems adjusting to freestalls when first introduced, resulting in a marked reduction in lying time and increased abnormal behaviors such as lying in the alley or lying backward in a stall. Our objective was to evaluate 2 strategies to ease the transition of heifers to freestalls: using an older, experienced heifer as a social model [experiment (Exp.) 1] or using brushes mounted in the stalls as an attractant (Exp. 2). In Exp. 1, 44 naïve heifers (129 ± 37 d of age, mean ± standard deviation) were assigned in pairs (n = 11 pairs/treatment) to either the control or social model (with an older heifer, 200 ± 24 d of age, as an experienced social companion) treatments. In Exp. 2, 52 naïve heifers (146 ± 9 d of age) were preassigned in pairs (n = 13 pairs/treatment) to either control or brush treatments. In both studies, heifers were initially housed in pens with a bedded pack (for 5 and 7 d in Exp. 1 and 2, respectively) before moving to pens in the same barn with sand-bedded freestalls. On d −2, 0, and 4 relative to the move to the freestalls, standing, perching (with the front hooves on the bedding and rear hooves in the alley), and lying (location: bedding vs. alley; direction in stall on d 0 and 4: forward or backward) were recorded at 5-min intervals. In addition, starting on d 0 relative to the move, latency to first lie down in a stall was recorded continuously. In both studies, time budgets did not differ between treatments. On the day heifers were moved, they spent less time lying relative to d −2 [Exp. 1: −1.8 h/d, standard error (SE): 0.4 h/d; Exp. 2: −3.0 h/d, SE: 0.3 h/d] and more time standing and perching. By d 4, lying and standing returned to d −2 baseline levels, although heifers continued to spend more time perching. When heifers moved to freestalls, no treatment differences were observed in the latency to lie down in a stall, but latencies differed between Exp. 1 (averaging approximately 3.8 h across treatments) and Exp. 2 (averaging 31.4 h across treatments). After moving to freestalls, the percentage of total lying time that heifers spent facing forward in a stall increased (Exp. 2: 53 vs. 77%, SE: 7%) or tended to (Exp. 1: 84 vs. 92%, SE: 3%) between d 0 and 4 of exposure, with no effect of treatment. Although lying behavior improved with days of exposure to freestalls, some heifers continued to lie down in the alley or backward in a stall, suggesting the need for additional work to ease the adjustment to freestall housing.

Measuring Calves' Usage of Multiple Environmental Enrichment Objects Provided Simultaneously

This study aims to assess calf usage of five potential enrichment devices provided simultaneously. We used 25 weaned Holstein-Friesian calves housed in groups of five (five replicates), and their behavior was recorded continuously with video cameras. This longitudinal observational study used a pen equipped with a mechanical and fixed brush, cowhide, and horizontal and vertical ropes. Data collected included how many visits each object received per day, the type of object usage, and the duration of the visits. Calves used all five objects at least once, and they used items more during the daytime than at night. Brushes were used mainly for grooming (e.g., rubbing or scratching), while ropes and cowhide for oral interactions (e.g., licking, chewing, and biting), most likely to lack oral stimulations that would naturally be satisfied by suckling and grazing at this age. The objects most frequently used were the mechanical brush and the horizontal rope, and they received the highest number of visits (214.9 and 154.9 bouts/day, respectively). The least chosen object was the stationary brush, which had the lowest number of visits (62.9 bouts/day). The provision of multiple enrichment objects for weaned calves should be considered as they may add complexity and novelty to barren environments.

Understanding Behavioural Development of Calves in Natural Settings to Inform Calf Management

Simple Summary

Animal welfare research is intended to address societal concerns regarding animal care, including natural living concerns. We reviewed the literature on calf behaviour when reared in more naturalistic outdoor systems with their mothers and herd. Understanding calf behaviour in more natural settings may help inform changes in calf management and housing that promote behaviours important to calf welfare.

Abstract

One important type of animal welfare concern is “natural living” (i.e., that animals are able to express natural behaviours that are important to them, and to engage with aspects of the natural world that they find important). The aims of this narrative review were to describe the behavioural development of calves (Bos taurus) in natural settings and use this to identify characteristics of natural systems that may be important to consider relative to this natural living conception of animal welfare. At birth, calves are licked by their mothers and soon stand to suckle for colostrum, and during the milk-feeding period, calves spend much of their time lying down. In natural systems, calves perform a variety of social behaviours with herd-mates, and slowly transition from their mother’s milk to eating solid food, by gradually increasing time spent grazing and ruminating. In contrast, on most commercial dairy systems, dairy calves are removed from their mothers at birth, housed individually, fed restricted amounts of milk and weaned abruptly at a young age. The results of this review suggest that accommodating key natural behaviours, for example through the use of teat feeding of milk, social housing, and gradual weaning, can help address welfare concerns.

Stationary brush use in naive dairy heifers

Weaned dairy heifers are often housed in environments with few appropriate outlets for grooming or oral manipulation. Our objective was to characterize brush use by naive heifers, including patterns over time. In phase 1, groups of 4 heifers (n = 13 groups, 146.4 ± 9.1 d old, mean ± standard deviation; SD) were introduced to a bedded pack pen with 4 wall-mounted brushes (25.4 × 6.0 cm with 3.8-cm-long bristles). On d 1, 2, and 6 of exposure, continuous video recordings were used to observe 2 focal heifers per group for brush use (oral manipulation, grooming, and the sum of total brush use; all averaged at the group level). Latency to use a brush upon entering the pen was 3.4 ± 4.9 min (mean ± SD; range: 0.1 to 17.8 min among individuals). Heifers used the brushes for oral manipulation (39.7 ± 17.5% of brush use, mean ± SD) and grooming (60.3 ± 17.5%), primarily of their heads (89.9 ± 5.4% of grooming). In phase 2, heifers were moved in pairs (n = 13 pairs/treatment) to freestall pens either with (brush treatment) or without (control) brushes mounted inside the stalls for the first 5 d of phase 2 (d 8-12 of the study); on the last day (d 13 of the study), brushes were provided in both treatments. On d 8 (brush treatment) and 13 (both treatments), one focal heifer/pen was recorded for the same behaviors as in phase 1. Linear mixed models were used to evaluate brush use patterns across days (phase 1: d 1, 2, and 6; phase 2 brush treatment: d 8 vs. 13) and between treatments on d 13. In phase 1, brush use was greatest on d 1 [45.9 min; 95% confidence interval (CI): 33.2-63.3 min, back-transformed from natural-log values], decreased on d 2 (25.0 min, 95% CI: 18.4-34.0 min), but then remained steady until d 6 (21.0 min, 95% CI: 15.4-28.5 min); the initial reduction in total brush use was due to changes in grooming, but oral manipulation remained relatively static. In phase 2, heifers in the brush treatment showed similar usage on d 8 versus d 13 (3.8 vs. 3.7 min, 95% CI: 1.9-6.8 vs. 1.9-6.5 min). Compared with heifers with continuous brush access on d 8-12, those in the control treatment showed more brush use on d 13, both for oral manipulation (6.6 vs. 2.5 min, 95% CI: 3.8-11.1 vs. 1.3-4.5 min) and grooming (3.5 vs. 1.2 min, 95% CI: 1.9-5.7 vs. 0.5-2.3 min). Our study is the first to characterize stationary brush use in weaned dairy heifers. We conclude that, despite lacking previous experience, heifers use brushes for both grooming and oral manipulation.

Early weaning: new insights on an ever-persistent problem in the dairy industry

It is common practice in the dairy industry to separate the calf from the cow immediately after parturition, and in most parts of the world calves are housed individually during the milk-feeding period. Early and abrupt separation has major implications for the calf's physical and psychological development. In this Research Reflection short review we present and discuss the main housing systems and management practices regarding early weaning in today's dairy industry. Main benefits and disadvantages are critically addressed, and possible future research suggested. Furthermore, major policy issues related to consumers, scientific recommendations and economic performance of farms have been identified, as well as future drivers for more viable housing solutions for neonatal calves. This review serves as an introduction and preamble to the second section of this Special Issue, which is dedicated to cow-calf contact management systems.

The effect of individual versus pair housing of dairy heifer calves during the preweaning period on measures of health, performance, and behavior up to 16 weeks of age

Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing. However, there is little evidence to suggest that pair-housed calves maintain their social and growth advantages past the weaning phase. The objective of this study was to investigate the effect of pair housing on measures of calf performance, health, and behavior up to 16 wk of age. Healthy Holstein and crossbred heifer calves were enrolled in the study after colostrum feeding, with the first calf randomly assigned to 1 of 2 housing treatments: pair (PR; 2 hutches with common outdoor space) or individual (INDV; 1 hutch plus outdoor space). All calves were bucket fed 4 L of milk replacer twice daily and weaned at 50 d of age. Weaned calves (6/group) remained with their treatment group until exit from the study at 16 wk. A venous blood sample was collected from each calf between 24 h and 7 d of age to test for serum total protein (g/dL). Body weights (kg) were obtained at birth, weaning, and 16 wk. Each enrolled calf was scored for health each week and calf health treatments were also collected. A hair sample was collected from the left shoulder at birth and 16 wk to assess hair cortisol (pg/mL). At enrollment, each calf was fitted with a triaxial accelerometer on the left hind leg for continuous recording of standing and lying time (min/24 h) for 16 wk. Latency to find feed, water, and lie down (min) at entrance to the weaned pen were recorded by continuous video observation. Open field testing with a novel object was performed at 5, 10, and 16 wk. Behaviors analyzed by video observation included latency to approach the object (s), vocalizations (n), and time spent immobile, walking, or running (s/10 min). Linear mixed models were used to determine the effect of treatment (INDV or PR) on calf growth, activity, and behavioral outcomes, which accounted for time, breed, the interaction of time and treatment, the random pen, and variability in testing day and repeated measurements within calf when appropriate. Twenty-four Holstein and crossbred calves (PR: n = 12, 6 pairs; INDV: n = 12) were enrolled from November 2 to December 23, 2018. The PR calves were 7.1 kg heavier at weaning and gained 0.15 kg/d more during the preweaning period as compared with INDV calves. In the 24 h after movement to the postweaning pen, PR calves lay down for longer periods of time (14.3 vs. 11.0 ± 0.4 h/d), and PR calves urinated more during novel object testing at 5 wk of age. Our study demonstrated benefits, such as better growth and increased lying time, of pair housing calves during the preweaning period.

Antimicrobial Effect of Zophobas morio Hemolymph against Bovine Mastitis Pathogens

Coliforms and Staphylococcus spp. infections are the leading causes of bovine mastitis. Despite extensive research and development in antibiotics, they have remained inadequately effective in treating bovine mastitis induced by multiple pathogen infection. In the present study, we showed the protective effect of Zophobas morio (Z. morio) hemolymph on bovine mammary epithelial cells against bacterial infection. Z. morio hemolymph directly kills both Gram-positive and Gram-negative bacteria through membrane permeation and prevents the adhesion of E. coli or the clinically isolated S. simulans strain to bovine mammary epithelial (MAC-T) cells. In addition, Z. morio hemolymph downregulates the expression of nucleotide-binding oligomerization domain (NOD)-like receptor family member pyrin domain-containing protein 3 (NLRP3), caspase-1, and NLRP6, as well as inhibits the secretion of interleukin-1β (IL-1β) and IL-18, which attenuates E. coli or S. simulans-induced pyroptosis. Overall, our results suggest the potential role of Z. morio hemolymph as a novel therapeutic candidate for bovine mastitis.

Symposium review: Precision technologies for dairy calves and management applications

There is an increasing interest in using precision dairy technologies (PDT) to monitor real-time animal behavior and physiology in livestock systems around the world. Although PDT in adult cattle is extensively reviewed, PDT use for the management of preweaned dairy calves has not been reviewed. We systematically reviewed research on the use and application of precision technologies in calves. Accelerometers have the potential to be used to monitor lying behavior, step activity, and rumination, which are useful to detect changes in behavior that may be indicative of disease, responses to painful procedures, or positive welfare behaviors such as play. Automated calf feeding systems can control delivery of nutritional plans to individualize feeding and weaning of calves; changes in feeding behaviors (such as milk intake, drinking speed, and unrewarded visits) may also be used to identify early onset of disease. The PDT devices also measure physiological and physical attributes in dairy calves. For instance, temperature monitoring devices such as infrared thermography, ruminal boluses, and implanted microchips have been assessed in calves, but no herd management-based commercial system is available. Many other PDT are in development with potential to be used in dairy calf management, such as image and acoustic-based monitoring, real-time location, and use of enrichment items for monitoring positive emotional states. We conclude that PDT have great potential for application in dairy calf management, enabling precise behavioral and physiological monitoring, targeted feeding programs, and identification of calves with poor health or behavioral impairments. We strongly encourage further development and validation of commercially available technologies for on-farm application of the monitoring of dairy calf welfare, performance, and health.

Effects of access to stationary brushes and chopped hay on behavior and performance of individually housed dairy calves

Providing individually housed dairy calves with opportunities for a greater range of natural behaviors, including foraging and grooming, has broad benefits for their behavioral development and performance. We evaluated the effects of providing hay and stationary brushes on performance and time engaged in feeding, grooming, and nonnutritive oral behaviors. Holstein calves were individually housed and assigned at 14 d of age to 1 of 4 treatments providing: a stationary brush (n = 10), chopped coastal bermudagrass hay (n = 9), both a stationary brush and chopped bermudagrass (n = 10), or no brushes nor additional feed (n = 10). Calves had ad libitum access to calf starter and water and were provided 8 L/d pasteurized waste milk fed in 2 meals via a teat bucket. Beginning at 43 d of age, calves were weaned across 10 d. Solid feed intake was measured daily, and growth parameters and cleanliness were measured weekly. Behavioral data were collected on 2 consecutive days at 25 ± 3 d, recorded continuously from video within daylight for 12 h. Provision of hay tended to increase solid feed intake and average daily gain during weaning, and calves provided a brush had improved coat cleanliness during weaning. Calves performed nonnutritive oral behavior, primarily directed toward the pen, with peaks in these abnormal behaviors around milk feeding. The duration of teat-directed nonnutritive sucking was reduced by access to either hay or a brush, compared with neither (3.2 vs. 6.8 min/12 h observation). Provision of a brush reduced pen-directed sucking (38.4 vs. 59.0 min/12 h observation), particularly at milk-feeding time, and also reduced standing time around milk feeding. Self-grooming was not affected by brush or hay access, but provision of the brush increased total time engaged in grooming behaviors (52.9 vs. 40.2 min/12 h observation). These results support benefits of accommodating natural foraging and grooming behaviors, yet reveal a high prevalence of nonnutritive oral behaviors in dairy calves. Overall, these findings underline the importance of environmental complexity in early rearing environments, and compel further consideration of behavioral needs of dairy calves to reduce the development of abnormal behaviors.

Key animal welfare issues in commercially raised dairy calves: social environment, nutrition, and painful procedures

Dairy calf welfare concerns are growing and new evidence suggests that the early life environment influences appropriate physical, behavioral, and cognitive development lasting into adulthood. This review highlights key evidence for the impacts of housing, diets, and painful procedures on calf welfare. We argue that these topics are currently critical welfare concerns, but are not the only points of concern. In addition to environmental requirements to maintain optimal health, dairy calves experience other challenges including social and nutritional restrictions. Individual housing is associated with impaired behavioral development and cognitive ability. Pair and group housing can mitigate some of these negative effects and should be encouraged. Restrictive milk allowances (<15% of body weight) lead to poor growth and hunger; these welfare concerns can be addressed with proper enhanced milk allowances and gradual weaning programs. Finally, dehorning is a critical animal welfare issue when pain control is withheld; calves show negative behavioral, physiological, and emotional responses during and after dehorning. The combined use of local anaesthetics and analgesics can mitigate these effects. An industry shift toward providing social companionship, enhanced milk allowances, and pain control during painful procedures would help to improve the welfare of dairy calves in intensive commercial rearing facilities.

Effect of a mechanical grooming brush on the behavior and health of recently weaned heifer calves

Background

Calf stress at weaning and during transition to group pens represents a concern in dairy operations. Favoring natural behaviors, such as grooming, may help on reducing this challenge. Our objective was to evaluate the effect of a mechanical grooming brush on behavior and health of recently weaned calves, after transferring from individual to group housing. Two treatment groups (control [CON, n = 81]; automated brush [AB, n = 81]) were compared enrolling Holstein heifers (94 ± 7 d old) that were monitored for 20 days. Four cohorts, considering one CON and one AB group (19–20 calves/pen/cohort) were enrolled sequentially. Each calf was weighed, clinically evaluated, and affixed with a 3-D accelerometer sensor attached to the ear at enrolment. Continuous measurements (min/h) were generated for the following behaviors: Not-active, active, highly active, eating, and ruminating. Cameras for continuous video recording were installed in each pen, and calves were weighted at the last day of the study (d 20). Behavioral data were summarized as daily averages (min/h). Data was examined using repeated measures analysis for nested factors, with day as the time unit.

Results

Overall, calves had their first interaction with the brush within 2.5 days with a mean (SE) of 7 (±9.6) h after being transferred to group pens. A significant effect was determined for the interaction day by treatment on the time spent not-active and eating. Average not-active time was greater in CON compared to AB (22.8 ± 0.82 min/h vs. 21.7 ± 0.82 min/h), while eating time was greater in AB compared with CON (7.01 ± 0.40 min/h vs. 6.43 ± 0.40 min/h). Treatment groups had a similar weight gain and time to the first disease.

Conclusions

We concluded that the use of a mechanical brush influenced behavior, reducing not-active time, while increasing eating time. The consequences of this change in activity require further investigation.