Effects of mixing on drinking and competitive behavior of dairy calves

Graduate Student Literature Review: Social and feeding behavior of group-housed dairy calves in automated milk feeding systems

Automated milk feeders (AMF) allow farmers to raise calves in groups while generating individual records on milk consumption, drinking speed, and frequency of visits. Calves raised in groups benefit from social interaction, which facilitates learning and adapting to novelty. However, calves in large groups (>12 calves/feeder) experience a higher risk of disease transmission and competition than those housed individually or in smaller groups. Therefore, if group size, grouping strategy, and disease detection are not optimal, the health and performance of calves can be compromised. The objectives of this narrative literature review, from publications available as of February 2023, are to: 1) describe the use of AMF in group housing systems for calves and the associated feeding behavior variables they automatically collect, 2) linking feeding behavior collected from AMF to disease risk in calves, 3) describe research on social behavior in AMF systems, and 4) introduce social networks as a promising tool for the study of social behavior and disease transmission in group-housed AMF-fed calves. Existing research suggests that feeding behavior measures from AMF can assist in detecting bovine respiratory disease (BRD) and enteric disease (ED), which are common causes of morbidity and mortality for pre-weaned dairy heifers. AMF records show reduced milk intake, drinking speed, or frequency of visits when calves are sick. However, there are discrepancies between published research about the sensitivity of feeding behavior measures as indicators of sickness, likely due to differences in feeding plans and disease detection protocols. Therefore, considering the influence of milk allowance, group density, and individual variation on the analysis of AMF data is essential to derive meaningful information used to inform management decisions. Research using dynamic social networks derived from precision data show potential for the use of social network analysis (SNA) to understand disease transmission and the effect of disease on social behavior of group-housed calves.

Graduate Student Literature Review: The problem of calf mortality on dairy farms

Calf mortality can be used as an indicator of animal health and welfare on dairy farms. However, several challenges surround the estimation and reporting of this metric, specifically: (1) lack of records or reliable data, (2) methods of data collection, and (3) inconsistencies in calculation and definitions used. Therefore, despite its importance, the lack of consensus on a definition of calf mortality makes it difficult to compare mortality rates between dairy farms or studies. Monitoring factors associated with calf mortality is vital to create preventative strategies. Although common strategies have been set about how to raise dairy calves and manage dairy calves, discrepancies among studies evaluating factors associated with calf mortality still exist. This review summarizes research on the evaluation of calf mortality and associated risk factors, specifically, the lack of reliable data and standardization of the definition of calf mortality. In addition, current strategies to monitor and prevent calf mortality will be presented in this review.

Environmental and biological factors that influence feeding behavior of Holstein calves in automated milk feeding systems

Automated milk feeders (AMF) used for dairy calves continuously provide individual feeding behavior measurements. The objective of this retrospective cohort study was to evaluate the association between temperature-humidity index (THI), birth weight, and dam parity characteristics on feeding behavior (i.e., milk consumption and drinking speed). Historical data sets generated from a single commercial dairy farm, where healthy (not treated for bovine respiratory disease, enteric disease, or injury) Holstein calves were fed up to 24 L/d of milk, were used for the analysis. A total of 5,312 female Holstein calves born between August 2015 and August 2021 (mean birth weight ± standard deviation: 40.7 ± 4.7 kg) on a commercial dairy farm were fed up to 24 L/d of nonsaleable milk for the first 32 d. For the analyses, feeding behavior data from the AMF system were combined with demographic data from the farm management software, and weather records from the closest public weather station (7 km away). Linear mixed models used to analyze daily milk consumption and drinking speed included THI, birth weight, dam parity, and feeding day as fixed effects, and feeder and calf within feeder as random effects. These models explained 57% of the total variation in milk consumption and 48% of the variation in drinking speed. Calves born from primiparous cows had the lowest milk consumption and the greatest drinking speed in comparison to calves born from multiparous cows. Calves with heavier birth weights had higher milk consumption and faster drinking speed than lighter calves. Drinking speed was negatively associated with THI. Including data derived from individual calves and their environmental conditions in data sets exploring feeding behavior from AMF would control for variation and improve the predictive models for performance assessment.

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.

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.

Effects of early social contact on dairy calf response to initial social grouping and regrouping

Social contact affects social development and response to novelty in dairy calves, but the age of introduction to social housing varies on-farm and may have implications for behavioral development and response to social grouping. The objective of this experiment was to evaluate the effects of early social contact during approximately the first 2 wk of life on calf early life behavior and performance and responses following initial social regrouping, followed by subsequent regrouping. At birth, calves were randomly assigned to individual (IH; n = 16 calves) or pair-housing (PH; n = 8 pairs). Calves were mingled between treatments and initially grouped (4 calves/pen) at 13 ± 2 d of age (mean ± standard deviation) and then regrouped (8 calves/pen) at 20 ± 5 d of age. Calf ability to learn to feed independently from the teat bucket in early life, and from the autofeeder following grouping, was monitored. Calf health, feed intake, and weight gain were recorded throughout the first 3 wk of life. Activity and social interactions were continuously recorded from video for the first 24 h following grouping and regrouping (except for allogrooming, hay consumption, and social play, which were observed for 12 h due to nighttime visibility). During the period of exposure to different housing treatments, calf feed intake and weight gain did not differ, but calves housed in pairs tended to scour for fewer days [4.1 vs. 5.6 d; PH vs. IH; standard error (SE) = 0.58]. Previously pair-housed calves spent more time lying socially (within 1 body length of another calf) than previously individually housed calves following both initial grouping (9.8 vs. 5.7 h/d; PH vs. IH; SE = 0.83) and regrouping (11.3 vs. 9.1 h/d; PH vs. IH; SE = 1.1). We saw no effects of previous social contact on duration of brush use (31.5 min/d; SE = 4.2), hay feeding (5.1 min/12 h; SE = 1.6), allogrooming (4.1 min/12 h; SE = 0.16), or social play (0.52 min/12 h; SE = 0.19) following initial grouping or regrouping. However, previously pair-housed calves tended to have greater lying time after regrouping. These results suggest that early life social contact before social grouping in the first weeks of life may not greatly affect activity within the pen or active social interactions following the transition to group housing. However, persistent differences in duration of social lying suggests that early life social contact may influence overall comfort toward other calves following social grouping.

Validation of 1-0 and instantaneous sampling for quantifying oral behaviors in milk-fed dairy calves

Oral behaviors, including feeding, drinking, grooming, and non-nutritive behaviors, are used as indicators of health and welfare in dairy calves, but continuous measurement of these behaviors can be labor intensive. Instantaneous sampling is often used to save labor but has only been validated for feeding behavior in calves. One-zero sampling may be an appropriate strategy well suited to capturing the rapid performance of non-nutritive behaviors. Our objective was to validate 1-0 and instantaneous sampling for measurement of oral behaviors around the time of bottle delivery against true values. Eleven Holstein heifer calves were housed individually, provided water, and fed a diet of starter grain and milk replacer (4.8-5.6 L/d step-up) via a bottle. When calves were 23 ± 7 d old, they were video recorded for 30 min before and after the morning 2.5 ± 0.2 L milk meal, from approximately 0900 to 1000 h. We measured ruminating, eating, drinking water, sucking milk, grooming, non-nutritive oral manipulation, and tongue flicks continuously and with instantaneous and 1-0 sampling at 5-, 10-, 30-, and 60-s intervals. We also examined the effect of instantaneous timing within these intervals. Estimates obtained through subsampling were compared with true values via regression analysis. The subsampling interval was determined to represent true values if the coefficient of determination ≥0.9, slope = 1, intercept = 0, and relative error <10%. Ruminating, drinking water, and eating were not performed by all 11 calves and were not included in the analysis. The proportions of time performing non-nutritive oral manipulation, grooming, and tongue flicks generated by continuous and 1-0 sampling were highly correlated but were consistently overestimated by 1-0 sampling, especially as calves spent more time engaged in these behaviors. Sucking milk was accurately represented at intervals of less than 30 s, likely due to most sucking bouts continuing for at least 150 s at a time and low between-calf variability compared with the other behaviors. Different start times within a given instantaneous interval resulted in wide variance in discrepancies between subsampling and continuous recording for all behaviors. We conclude that around milk feeding, 1-0 sampling is an appropriate choice to represent stimulus-elicited behavior, such as sucking milk in a milk-restricted system. However, time engaged in short, highly variable, or intermittent behaviors is not reliably captured via instantaneous or 1-0 sampling in the hour around bottle delivery.

Effects of milk replacer meal size on feed intake, growth performance, and blood metabolites and hormones of calves fed milk replacer with or without butyrate ad libitum: A cluster-analytic approach

This study intended to classify ad libitum-fed calves according to their milk replacer (MR) meal size using the K-means clustering approach. This study aimed to investigate the effects of MR meal size on feed intake, growth performance, and blood metabolic and hormones of ad libitum MR-fed calves. German Holstein calves (16 male and 16 female) were studied from birth until d 77 of age. All calves received first colostrum (2.5 kg) milked from their dams within 2 h after birth. Subsequent colostrum meals (subsequent 4 meals until 2.5 d of age; 2 meals/d) and MR (125 g of powder/L; 21.7% crude protein, 18.6% crude fat) were fed ad libitum by teat bucket until d 10 ± 2 of age. Afterward, calves were housed in group pens with automatic feeders for MR (maximum of 25 L/d) and concentrate from 10 ± 3 d of age. Half of the calves received MR supplemented with butyrate to improve growth performance. Milk intake was stepped down to 2 L/d from wk 9 to 10, and 2 L/d of MR were offered until the end of the study. On d 1, 2, 4, and 7, and then weekly until wk 11 of age, blood samples were collected for measurement of metabolites and hormones related to energy metabolism and growth. The K-means cluster analysis on the MR meal size data collected from the automatic feeder resulted in 3 clusters (n = 14, n = 12, and n = 6). Two clusters with a sufficient cluster size (n = 14 and n = 12) were included for further statistical analysis using repeated measures mixed-model ANOVA. In both clusters, butyrate supplementation was equally distributed and failed to affect a difference in MR meal size. Cluster 1 showed calves with higher MR meal size (HI; 2.2 ± 0.11 L/visit of MR) and cluster 2 with lower meal size (LO; 1.8 ± 0.07 L/visit of MR) supplemented MR without (HIB-; n = 6; LOB-, n = 7) or with 0.33% calcium-sodium butyrate (HIB+; n = 6; LOB+, n = 7). Dry matter intake of MR did not differ between HI and LO, but intakes of concentrate and total dry matter tended to be greater in HI than in LO and increased more distinctly in HI than in LO at the end of the study. The average daily gain (g/d) was greater in HI than in LO. Plasma concentrations of total protein (g/L), albumin (g/L), glucose (mmol/L), urea (mmol/L), insulin (µg/L), and glucagon (ng/L) were higher, and the concentrations of insulin-like growth factor I tended to be higher, in HI than in LO calves. Plasma β-hydroxybutyrate was higher in LO than in HI at d 63 and lower in calves fed MR with butyrate at d 77. In conclusion, clustering analysis discriminates 2 main groups of calves with different MR meal size and indicates an effect of MR meal size on solid feed intake, growth performance, and metabolic changes.

Stress, strain, and pregnancy outcome in postpartum cows

Stress affects the productivity and fertility of cattle. Stress causes strain and individual animals experience different amounts of strain in response to the same amount of stress. The amount of strain determines the impact of stress on fertility. Typical stresses experienced by cattle include environmental, disease, production, nutritional, and psychological. The effect of stress on the reproductive system is mediated by body temperature (heat stress), energy metabolites and metabolic hormones (production and nutritional stresses), the functionality of the hypothalamus-pituitary-gonadal (HPG) axis and (or) the activation of the hypothalamus-pituitary-adrenal (HPA) axis. The strain that occurs in response to stress affects uterine health, oocyte quality, ovarian function, and the developmental capacity of the conceptus. Cows that have less strain in response to a given stress will be more fertile. The goal for future management and genetic selection in farm animals is to reduce production stress, manage the remaining strain, and genetically select cattle with minimal strain in response to stress.

Should Animal Welfare Regulations Be More Restrictive? A Case Study in Eight European Union Countries

Simple Summary

Intensive animal production systems are compromising current animal welfare standards. European societies’ growing concerns regarding how animals are raised have resulted in continuous European Union (EU) policy reforms that have banned certain intensive farming methods. We investigated whether EU respondents, differentiated by their roles as citizens and consumers, believe that the current regulations on animal welfare should be more restrictive. Data were collected using a survey approach implemented in eight European countries (Spain, the United Kingdom, Poland, Greece, Lithuania, Romania, Italy, and Sweden) with a sample of 3860 respondents. The results show that women citizens are more concerned with animal welfare and are prone to accept more restrictive regulations. Respondents from northern European countries (Poland and Sweden) are willing to accept regulations that are more restrictive than the current minimum standards than respondents from southern countries (Spain and Italy). Our results suggest that increasing knowledge of animal welfare is related to effective information campaigns that use the Internet to endorse the current animal welfare legislation.

Abstract

Increasingly, intensive livestock production systems have increased societal concern regarding the current animal welfare standards. We investigated whether individuals in their roles as consumers and citizens believe that the current European regulations regarding animal welfare should be more restrictive. Factors affecting this decision were assessed by analyzing respondents’ understanding of animal welfare-related issues, their subjective and objective knowledge levels, the credibility they assign to different information sources, their perceptions toward the current restrictiveness of animal welfare standards, and their socioeconomic characteristics. Data were collected using a semi-structured questionnaire distributed in eight European Union (EU) countries (Spain, the United Kingdom, Poland, Greece, Lithuania, Romania, Italy, and Sweden) with 3860 total responses. The results showed that consumers are more reluctant to adopt more restrictive regulations than respondents in the role of citizens. Respondents from northern European countries (Poland and Sweden) are more likely to support regulations that are more restrictive than the current minimum requirements than respondents from southern countries (Spain and Italy). Women were found to be more concerned with the welfare of pigs and laying hens—lending credibility to the Internet as an information source—and were more likely to support more restrictive animal welfare legislation.

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.

Analysis of pre-weaning feeding policies and other risk factors influencing growth rates in calves on 11 commercial dairy farms

Growth rates in pre-weaned calves influence their health, age at first calving and lifetime productivity. Many farms restrict milk rations to encourage solid feed intake and facilitate early weaning, but this can compromise growth. This study determined the milk feeding policies and associated growth rates on 11 commercial dairy farms in South East England, each following their normal management regime. Between 26 and 54 heifers were recruited per farm, providing a final cohort of 492, of which 71% were pure Holstein. Information on calf rearing practices (feeding, weaning, housing) and health was collected via questionnaires and weekly observations. Estimates of actual milk fed (kg solids) between 1 and 63 days were calculated for individual calves. Morphometric data (weight, height, length) were taken at weeks 1, 5 and 9 and at a median age of 7.5 months and growth rates were calculated. Most calves were fed milk replacer via automated feeders (four farms), teat feeder (one) or buckets (four) whereas two farms provided drums of acidified waste milk. Farms fed between 4 and 6 l/day of milk at mixing rates of 10% to 15%, providing 400 to 900 g/day of milk solids. Both skeletal growth rates and average daily weight gain (ADG) increased in the second month of life compared with the first: height growth from 0.17±0.14 to 0.25±0.16 cm/day and ADG from 0.48±0.25 to 0.71±0.28 kg/day. Post-weaning heifers up to 7.5 months had height increases of 0.16±0.035 cm/day and ADG of 0.83±0.16 kg/day. From 1 to 63 days 70% of calves had growth rates <0.7 kg/day and of these 19.6% gained <0.5 kg/day. Mean ADG before 9 weeks varied between farms from 0.52±0.30 to 0.75±0.20 kg/day. This was related to the amount of milk fed at both a farm and individual calf level. Increasing the total milk solids fed between 1 and 63 days from 20.4 to 46.3 kg (the 10th to 90th percentile observed) was associated with an increase of 0.11 kg/day ADG. All farms had a wide variation in growth rates despite single feeding policies. Higher circulating immunoglobulin G and IGF1 concentrations were associated with better growth, whereas low temperatures in month of birth, high scores for diarrhoea, respiratory and umbilical disease and large birth size reduced growth. Many commercially grown dairy heifers therefore experienced growth restriction in the pre-weaned period, potentially reducing their health, welfare and productivity.

Efficacy of tildipirosin metaphylaxis for the prevention of respiratory disease, otitis and mortality in pre-weaned Holstein calves

The aim of this study was to evaluate the efficacy of two metaphylactic approaches (long acting antibiotic injected once at 10 days of life or twice at 10 and 35 days of life) on the prevention of bovine respiratory disease (BRD), otitis and mortality in high-risk group-housed pre-weaned Holstein heifer calves. The antibiotic of choice for the metaphylactic approach was a long acting macrolide (tildipirosin) administered subcutaneously at the base of the neck at a dose of 1 mL per 45 kg body weight. A clinical trial was carried out on one dairy farm with random allocation of newborn calves to one of three treatments: (1) control (CTR); (2) one injection at 10 days of life (M1); and (3) two injections at 10 and 35 days of life (M2). Study heifers (n = 795) were reared in group pens of 25 calves per pen and fed unrestricted acidified non-saleable milk from day 1 to day 65 of life. Cox proportional hazard and general linear mixed models were used to evaluate the effect of treatment on mortality, BRD and otitis, and average daily weight gain. The birth weights, proportions of calves with inadequate transfer of passive immunity, proportions of calves born from primiparous dams and proportions of calves born from assisted parturitions were not different among CTR, M1 and M2 treatments. A significantly lower hazard of being affected with BRD and/or otitis (but not for BRD or otitis alone) was observed for M1 (hazard ratio, HR = 0.70, P = 0.009) and M2 (HR = 0.72, P = 0.01) when compared to the CTR group. Metaphylactic treatments had no effect on mortality, otitis and average daily weight gain during the pre-weaning period.

Models and Methods to Investigate Acute Stress Responses in Cattle

There is a growing appreciation within the livestock industry and throughout society that animal stress is an important issue that must be addressed. With implications for animal health, well-being, and productivity, minimizing animal stress through improved animal management procedures and/or selective breeding is becoming a priority. Effective management of stress, however, depends on the ability to identify and quantify the effects of various stressors and determine if individual or combined stressors have distinct biological effects. Furthermore, it is critical to determine the duration of stress-induced biological effects if we are to understand how stress alters animal production and disease susceptibility. Common stress models used to evaluate both psychological and physical stressors in cattle are reviewed. We identify some of the major gaps in our knowledge regarding responses to specific stressors and propose more integrated methodologies and approaches to measuring these responses. These approaches are based on an increased knowledge of both the metabolic and immune effects of stress. Finally, we speculate on how these findings may impact animal agriculture, as well as the potential application of large animal models to understanding human stress.

Effect of preweaned dairy calf housing system on antimicrobial resistance in commensal Escherichia coli

Group housing of preweaned dairy calves is a growing practice in the United States. The objective of this practice is to increase the average daily gain of calves in a healthy and humane environment while reducing labor requirements. However, feeding protocols, commingling of calves, and occurrence of disease in different calf-housing systems may affect the prevalence of antimicrobial drug-resistant bacteria. This study evaluated the effect of a group pen-housing system and individual pen-housing system on antimicrobial resistance trends in fecal Escherichia coli of preweaned dairy calves and on the prevalence of environmental Salmonella. Twelve farms from central New York participated in the study: 6 farms using an individual pen-housing system (IP), and 6 farms using a group pen-housing system (GP). A maximum of 3 fecal E. coli isolates per calf was tested for susceptibility to 12 antimicrobial drugs using a Kirby-Bauer disk diffusion assay. Calves in GP had a significantly higher proportion of E. coli resistant to ciprofloxacin and nalidixic acid, whereas calves in IP had a significantly higher proportion of E. coli resistant to ampicillin, ceftiofur, gentamycin, streptomycin, and tetracycline. Calf-housing system had an effect on resistance to individual antimicrobial drugs in E. coli, but no clear-cut advantage to either system was noted with regard to overall resistance frequency. No outstanding difference in the richness and diversity of resistant phenotypes was observed between the 2 calf-housing systems.

Feeding behaviour of artificially reared Romane lambs

A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.