Randomized field trial on the effects of body weight and short transport on stress and immune variables in 2- to 4-week-old dairy calves

How many subjects are enough in a veterinary trial?-Literature review and insights from industrial statisticians

To approve veterinary medicines, regulatory agencies require substantial evidence of safety and effectiveness from well-designed trials. A critical consideration in planning a veterinary trial is to determine the requisite number of subjects needed to achieve the trial objective(s). Sample sizes for preclinical studies usually follow specific guidelines, whereas clinical studies should follow more rigorous requirements to determine the optimal sample size for detecting significant and meaningful treatment effects. This paper presents a descriptive literature review aiming to explore current reported practices in sample size calculation for published veterinary clinical trials. The review included articles published in 12 top-ranking veterinary health journals from January 1, 2013, to June 4, 2023, sourced from PubMed and Medline regarding animal trials. Initially, 294 articles were identified, of which 98 (33 %) focused on veterinary clinical studies. Among these 98 papers, only 24 (24 %) provided detailed methods on sample size calculations, with individual animals as experimental units across at least two arms. The predominant animal species studied in these trials were canines (39 %), cattle (32 %), and swine (21 %), with most studies aiming for a statistical power of at least 80 %. Unlike human clinical trials, the paper found that statistically rigorous sample size calculations were less commonly reported in animal clinical trials. Our paper provides recommendations for veterinary clinical trial practitioners and offers insights into how sample size determination can be properly conducted and reported. Furthermore, this article extends to discuss practical issues in sample size determination for preclinical studies.

Effects of dietary rumen-protected glucose level and taurine supplementation on weight change and oxidative stress state of yaks after transport

Rumen-protected glucose (RPG) and taurine (TAU) are crucial for the nutrition and physiology of ruminants, enhancing production performance and mitigating negative energy balance. This study aimed to assess the impact of RPG levels and TAU supplementation on the body weight, antioxidant capacity, immune function and stress responses in yaks before and after transport. Thirty-two healthy male yaks, aged 3 years and weighing 172.5 ± 10.2 kg, were randomly assigned to one of four dietary treatments: (1) low RPG and low TAU (LRLT), with 1% RPG and 5 g/d TAU; (2) low RPG and high TAU (LRHT), with 1% RPG and 15 g/d TAU; (3) high RPG and low TAU (HRLT), with 3% RPG and 5 g/d TAU; and (4) high RPG and high TAU (HRHT), with 3% RPG and 15 g/d TAU. The yaks were treated with the corresponding diet for 7 days, then received 9 h of transportation, and finally fed the same diet at their destination for 30 days. The weight was measured before and on days 0 and 30 after transport, and the plasma was collected before and on day 0, 10, and 30 after transport for analysis of biochemical, antioxidant, immune, and stress response indicators. We observed that transport increased plasma concentrations of total cholesterol, total protein, lactate dehydrogenase, creatine kinase, malondialdehyde, cortisol and lipopolysaccharides of yaks among treatments, while decreased their BW and plasma IL-10 concentration. Increasing TAU supplementation reduced weight loss (8.42 vs. 11.9 kg) and weight loss percent (4.83% vs. 6.87%) in yaks after transport. The concentration of MDA in plasma was lower in HRHT than in LRLT at day 0 after transport (p = 0.03). The activity of GSH-PX was higher in HRHT than in LRLT at day 10 after transport (p = 0.04). Concentrations of IL-10 at day 0 and 10 after transport was higher in HRHT than in LRLT and HRLT (p = 0.02, p = 0.01, respectively). With the increase of TAU supplementation, concentrations of IL-1β at day 30 after transport (p = 0.02), TNF-α at day 0 after transport (p = 0.02), COR at day 10 (p = 0.03) and 30 (p = 0.05) after transport as well as LPS at day 0 after transport (p = 0.04) decreased. In addition, concentrations of COR at day 0 after transport was lower in LRHT and HRHT than in LRLT (p = 0.03). Based on all the results, we demonstrated that increasing TAU supplementation levels reduced post-transport weight loss in yaks, improved their antioxidant capacity and immune function, and alleviated stress responses. Considering the effect of resistance to transport stress and costs, the optimal treatment identified in this study involved a diet containing 1% RPG and supplemented with 15 g/d TAU.

Exploring the effects of transport duration on the fecal microbial communities of surplus dairy calves

Transportation significantly affects the health and welfare of surplus dairy calves, largely due to the various stressors and pathogen exposures encountered during the process. Concurrently, an animal's microbiome is known to correlate with its health status, with stress-induced alterations in the microbiota potentially precipitating various diseases. This study aimed to compare the effects of transportation durations of 6, 12, or 16 h on the fecal microbiota in young surplus dairy calves. We used a randomized controlled design in which surplus dairy calves aged 1 to 19 d from 5 commercial dairy farms in Ontario were allocated into 1 of 3 transportation groups (6, 12, and 16 h of continuous transportation). Health assessments were conducted before, immediately after, and for 2 wk following transportation. Fecal samples were collected before, immediately after, and at 24 and 72 h after transportation and subjected to 16S rRNA sequencing. Alpha diversity metrics showed no significant differences between the 3 transportation groups at any of the sampling time points. Although β diversity metrics revealed no clustering by transportation groups, they indicated significant differences across sampling time points within each group. The overall analysis revealed a total of 22 phyla and 353 genera, with Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria being the most abundant phyla. Bacteroides, Escherichia/Shigella, Lactobacillus, Collinsella, and Bifidobacterium were the most abundant genera. The reduction in Fusobacteria abundance before and after transport was significantly larger in the 16-h transportation group when compared with the 6-h transportation group. We also identified several genus-level and amplicon sequence variation-level taxa that displayed significant differences in their abundances across various transportation groups, observed at all sampling time points investigated. This research identifies microbiota changes due to varying transportation durations in surplus dairy calves, providing a broad understanding of the microbial shifts in surplus dairy calves after transportation across varying durations. Although these variations may not directly correlate with overall calf health or indicate dysbiosis, these results emphasize the importance of further investigating transportation practices to enhance calf health and well-being. Further studies are warranted to elucidate the relationship between microbiota and calf health.

Abomasitis associated with halofuginone intoxication in pre-weaned calves

BACKGROUND

In this case series abomasitis as a consequence of halofuginone intoxication is suspected.

CASE PRESENTATION

Seven Belgian-Blue calves with complaints of anorexia and weight loss were presented to an university clinic. Ultrasonography showed thickening and edema of the abomasal wall in all cases, suggesting abomasitis. Abomasitis was confirmed on necropsy in three cases. Retrospective analysis clarified the uptake of an overdose of halofuginone lactate (348-421 µg/kg/day). Four animals fully recovered after removal of halofuginone lactate administration, therapy for comorbidities (pneumonia, diarrhoea) and supportive therapy.

CONCLUSION

To the authors' knowledge, this case series is the first report associating halofuginone lactate use with abomasitis. This was suspected after clinical improvement of four of the presented animals after terminating the administration of a high dose of halofuginone lactate, and exclusion of other possible causes. Underlying mechanisms are still unclear.

Effect of source and journey on physiological variables in calves transported by road and ferry between Ireland and the Netherlands

This study aimed to establish baseline variables for calves transported by road and ferry from Ireland to the Netherlands and to investigate the effect of journey [two comparable journeys in April (J1) and May (J2) 2022] and source [source farm or mart (SF/MA)] on these variables. A total of 66 calves from the SF/MA were transported from Ireland to commercial veal farms in the Netherlands. Blood samples were collected at the SF/MA, assembly center (Ireland), lairage (France), and on arrival on the veal farm (Netherlands). They were analyzed for indicator variables related to energy balance, hydration/electrolytes, physical/muscular stress, immunity, and inflammation [glucose, beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), potassium, sodium, magnesium, chloride, urea, haematocrit, total protein, creatine kinase, L-lactate, cortisol, white blood cell, neutrophil, lymphocyte and monocyte counts, serum amyloid-A, and haptoglobin]. Health variables eye and nose discharge, skin tent (a measure of dehydration), and navel inflammation were scored by a trained observer, and calves were weighed at every blood-sampling time point. All blood variables and body weight changed significantly (P < 0.05) during transport, most notably between the assembly center and lairage. Reference ranges were available for 18 variables; 11 of these variables exceeded the reference ranges at the lairage, whilst 10 variables exceeded the reference ranges on arrival at the veal farm. However, health variables did not change during transport. A journey-to-journey comparison indicated much variation; 18 out of 25 variables differed significantly on at least one time point. In total, J1 calves experienced a more severe change in BHB, potassium, strong-ion-difference, L-lactate, and eye and nose discharge than J2 calves. The source of calves also affected their physiology; 12 out of 25 variables studied differed significantly, all of which were confined to the first time point. Specifically, MA calves had elevated levels of NEFA, urea, haematocrit, L-lactate, cortisol, white blood cell, neutrophil, and monocyte counts and lower levels of corrected chloride and lymphocyte count. Overall, calves in this study showed a generalized physiological disturbance beyond reference limits during long-distance transport, but no animal died during transport or for 3 weeks post-arrival.

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

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

EFSA Panel on Animal Health and Welfare (AHAW), Nielsen SS, Alvarez J, Bicout DJ, Calistri P, Canali E, Drewe JA, Garin‐Bastuji B, Gonzales Rojas JL, Gortázar Schmidt C, Michel V, Miranda Chueca MÁ, Padalino B, Pasquali P, Roberts HC, Spoolder H, Stahl K, Velarde A, Viltrop A, Winckler C, Earley B, Edwards S, Faucitano L, Marti S, de La Lama GCM, Costa LN, Thomsen PT, Ashe S, Mur L, Van der Stede Y, Herskin M. Welfare of cattle during transport

In the framework of its Farm to Fork Strategy, the Commission is undertaking a comprehensive evaluation of the animal welfare legislation. The present Opinion deals with protection of cattle (including calves) during transport. Welfare of cattle during transport by road is the main focus, but other means of transport are also covered. Current practices related to transport of cattle during the different stages (preparation, loading/unloading, transit and journey breaks) are described. Overall, 11 welfare consequences were identified as being highly relevant for the welfare of cattle during transport based on severity, duration and frequency of occurrence: group stress, handling stress, heat stress, injuries, motion stress, prolonged hunger, prolonged thirst, respiratory disorders, restriction of movement, resting problems and sensory overstimulation. These welfare consequences and their animal-based measures are described. A variety of hazards, mainly relating to inexperienced/untrained handlers, inappropriate handling, structural deficiencies of vehicles and facilities, poor driving conditions, unfavourable microclimatic and environmental conditions, and poor husbandry practices leading to these welfare consequences were identified. The Opinion contains general and specific conclusions relating to the different stages of transport for cattle. Recommendations to prevent hazards and to correct or mitigate welfare consequences have been developed. Recommendations were also developed to define quantitative thresholds for microclimatic conditions within the means of transport and spatial thresholds (minimum space allowance). The development of welfare consequences over time was assessed in relation to maximum journey duration. The Opinion covers specific animal transport scenarios identified by the European Commission relating to transport of unweaned calves, cull cows, the export of cattle by livestock vessels, the export of cattle by road, roll-on-roll-off ferries and 'special health status animals', and lists welfare concerns associated with these.

Preparing Male Dairy Calves for the Veal and Dairy Beef Industry

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

Characterizing the literature surrounding transportation of young dairy calves: A scoping review

Transportation is a stressful event for cattle, as it may involve various handling practices, commingling, deprivation of food and water, and fluctuating temperatures. Calves are particularly susceptible to these stressors because their physiological and immune systems are still developing. There has been no formal synthesis of the scientific literature evaluating the effect of transportation on young dairy calf health and performance; the aim of this scoping review is to describe and characterize this body of work. We targeted both descriptive and analytic studies examining transport of calves, including listing how the effect of transport has been evaluated. Eight databases were searched for relevant articles with eligible studies being primary research articles investigating transportation of calves of either sex who were younger than 60 d of age or weighed less than 100 kg. Two reviewers independently screened the title and abstracts of 6,859 articles with 361 potentially relevant articles screened at full text. Of these, 46 were relevant and had data extracted. Articles reporting study location were conducted in the United States (n = 5), Australia (n = 3), Japan (n = 3), and New Zealand (n = 3). Common transport-related variables evaluated included time in transit (n = 13), distance of transportation (n = 8), vehicle-related factors (n = 8), and age at time of transportation (n = 4). Outcome measures varied greatly, including blood parameters (n = 28), health assessments (n = 20), weight (n = 17), behavioral metrics (n = 14), mortality (n = 7), feed intake following transportation (n = 4), salivary cortisol concentrations (n = 3), morbidity (n = 3), and isolation of Salmonella Dublin in fecal samples (n = 2). Outcome parameters were measured during transport or ranged from immediately after to one year following transportation. As the transport-related risk factors and outcomes measured assessed varied widely between studies, future quantitative synthesis (e.g., meta-analysis) in this area may be limited. Several knowledge gaps were identified, including methods to prepare calves for transportation, such as improving nutrition, administering medication, or transporting calves at an older age or weight. Further research could also focus on consistent and clear reporting of key items related to study conduct and analysis, as well as the development of a core outcome set for calf transport studies.

Male dairy calf welfare: A Canadian perspective on challenges and potential solutions

Male dairy calf welfare is a key issue in the Canadian cattle industry. The welfare of male dairy calves can be explored through the aspects of health and biological functioning, affective states, and natural living. Presently, the main welfare issues associated with the production of male dairy calves include morbidity and mortality, colostrum and feeding management, transportation, isolation, castration and disbudding, and euthanasia. Opportunities to improve male dairy calf welfare include improving accepted industry practices, enhancing education and compliance with industry codes of practice, and increasing veterinarian involvement in on-farm animal welfare. The benefits of improving male dairy calf welfare include maintenance of the cattle industry's social license and improved producer mental health and occupational satisfaction. The main barriers to improving male dairy calf welfare are economics and cultural attitudes within the industry towards male dairy calves.

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

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

Calf and dam characteristics and calf transport age affect immunoglobulin titers and hematological parameters of veal calves

This study aimed to investigate effects of transport age of calves (14 vs. 28 d), and of calf and dam characteristics, on immunoglobulin titers and hematological variables of veal calves. Calves (n = 683) were transported to a veal farm at 14 or 28 d of age. Natural antibodies N-IgG, N-IgM, and N-IgA against phosphorylcholine conjugated to bovine serum albumin (PC-BSA) were measured in serum of the dams 1 wk before calving and in first colostrum. These antibodies were also measured in serum of calves 1 wk after birth, 1 d before transport, and in wk 2 and 10 posttransport at the veal farm. Hematological variables were assessed in calves 1 d before transport and in wk 2 posttransport. One day before transport, titers of N-IgG, N-IgM, N-IgA, and neutrophil counts were higher, and lymphocyte counts were lower in 14-d-old calves compared with 28-d-old calves. In wk 2 at the veal farm, calves transported at 14 d of age had higher N-IgG titers and neutrophil counts, but lower N-IgM and N-IgA titers, and lymphocyte counts than calves transported at 28 d. In wk 1 and 1 d before transport, N-Ig in calves were positively related to N-Ig in colostrum. In wk 2 and 10 at the veal farm, N-IgG in calves was positively related to N-IgG in colostrum. The N-IgG titers in calves at the dairy farm were negatively related to the likelihood of being individually treated with antibiotics or other medicines at the veal farm. Our results suggest that calves transported to the veal farm at 28 d of age showed a more advanced development of their adaptive immunity than calves transported at 14 d of age. Quality of colostrum might have long-term consequences for N-IgG titers and immunity in veal calves.

Invited review: The welfare of young calves transported by road

The transport of young calves is a welfare concern. Young calves aged ≤3 mo are particularly vulnerable to compromised welfare, and are at a relatively high risk of morbidity and mortality compared with adult cattle. Calves face several potential challenges to welfare during and after transport, including food and water deprivation, disease, injury, and stress from handling, social mixing, and new environments. The key risk factors identified for poor calf welfare associated with transport include long transport and fasting durations, young age at transport, poor colostral immunity, timing within the calving season, lack of bedding in trucks, and high stocking density. Maximizing calf welfare thus requires a multifaceted approach, such as minimizing transport and fasting durations, transporting at an appropriate stocking density with comfortable bedding, only transporting calves that are healthy and fit, and optimizing pre-transport calf management. More research is needed to understand the effect of transport on the mental or affective state of calves.

Factors affecting dairy calf price in auction markets in Québec, Canada: 2008-2019

Dairy calves not kept for replacement are sold at young age in Québec auction markets for white and grain-fed veal calf production. The province of Québec produces 80% of the Canadian veal meat, but little information is available on the factors associated with the calves' price per crude weight (Can$/kg; Can$1 = US$0.78 at time of writing). The characteristics of calves sold in Québec auction markets from 12 complete years (2008-2019) were retrospectively studied. The calves' weight, breed and sex, the year and season of sale, the auction site, as well as the estimated distance traveled between the farm of origin and the auction site were analyzed as potential covariates associated with calf price. Two multivariable logistic models associated with low sale value (below the 10th or the 25th percentile of the day price) and 2 models associated with good sale characteristics (above the 50th or the 75th percentile of the day price) were built. The median distance between the farm and the auction site was 52 km (interquartile range: 30-95 km). Only 5% of calves traveled distances greater than 220 km. The weight, breed, sex, and auction sites explained most of the variability in the different models. Distance traveled and multiple interactions were also significantly associated with the outcomes. Calves with body weight from 48 to <56 kg were sold in higher percentiles of the day than lighter or heavier calves. Beef-crossed calves had better sale prices than Holstein, whereas colored dairy calves had lower sale characteristics than both Holstein and beef-crossed calves. The effect of distance traveled was complex, varying depending on the model and interactions, and explained a small portion of the total deviance in every model. Calves traveling from distances ≥110 km had lower sale characteristics in summer and fall in the different studied models. This study gives relevant insights on calves' characteristics associated with good versus low sale prices in Québec auction markets.

Effects of pre-transport diet, transport duration and transport condition on immune cell subsets, haptoglobin, cortisol and bilirubin in young veal calves

The aim of this study was to investigate effects of pre-transport diets, transport durations and transport conditions on immune cell subsets, haptoglobin, cortisol and bilirubin of young calves upon arrival at the veal farm. An experiment was conducted with a 2 × 2 × 2 factorial arrangement with 3 factors: 1) provision of rearing milk or electrolytes at the collection center (CC); 2) transport duration (6 or 18 hours) and 3) transport condition (open truck or conditioned truck). Holstein-Friesian and cross-bred calves were used (N = 368; 18 ± 4 days; 45.3 ± 3.3 kg). Blood samples were collected from calves (N = 128) at the collection center, immediately post-transport (T0) and 4, 24, 48 hours, week 1, 3 and 5 post-transport. Blood was analyzed for cortisol, bilirubin, haptoglobin, IgG and IgM. Moreover, cell counts of neutrophils, lymphocytes, monocytes, basophils and eosinophils were measured in blood samples taken at the collection center and T0. In these same blood samples, different lymphocyte populations were characterized by flow cytometry, including CD14+ cells, NK cells, δγ+ T cells, CD8+ cells, CD4+ cells and CD21+ cells. Calves transported in the conditioned truck had higher amounts of white blood cell count (WBC) (Δ = 1.39 × 10⁹/l; P = 0.01), monocytes (Δ = 0.21 × 10⁹/l; P = 0.04), neutrophils (Δ = 0.93 × 10⁹/l; P = 0.003), than calves transported in the open truck regardless, of pre-transport diet or transport duration. The study showed that transport condition and duration influenced parts of the innate immune system of young veal calves. Cortisol, bilirubin and WBC seemed to be connected by similar underlying mechanisms in relation to transport conditions. However, it is unclear which specific pathways in the immune system of young calves are affected by different transport conditions (e.g. temperature, humidity, draught).

Effect of aerosolized bacterial lysate on development of naturally occurring respiratory disease in beef calves

Background

Bovine respiratory disease (BRD) is a major problem affecting beef cattle after arrival to feedlots. Alternatives to antibiotics are needed for prevention.

Hypothesis

Stimulation of pulmonary innate immune responses at the time of arrival to a feedlot reduces the occurrence and severity of BRD.

Animals

Sixty beef steers at high risk of BRD.

Methods

Randomized, double‐blinded, placebo‐controlled study. Calves received saline or a lysate of Staphylococcus aureus and Escherichia coli by aerosol, at 16 hours after feedlot arrival. Calves were monitored for 28 days for disease outcomes and levels of Mycoplasma bovis and Mannheimia haemolytica in nasal swabs.

Results

Death from M bovis pneumonia was significantly greater in lysate‐treated animals (6/29, 24%) compared to controls (1/29, 3%; odds ratio = 10.2; 95% confidence interval [CI] = 1.1‐96.0; P = .04). By 28 days after arrival, 29/29 lysate‐treated calves had ultrasonographic pulmonary consolidation compared to 24/29 control calves (P = .05). Lysate‐treated calves had lower weight gain compared to control calves (−8.8 kg, 95% CI = −17.1 to −0.5; P = .04), and higher body temperatures on days 4, 7, and 21 (0.19°C; 95% CI = 0.01‐0.37; P = .04). Nasal M bovis numbers increased over time and were higher in lysate‐treated calves (0.76 log CFU, 95% CI = 0.3‐1.2; P = .001).

Conclusions and Clinical Importance

Aerosol administration of a bacterial lysate exacerbated BRD in healthy high‐risk beef calves, suggesting that respiratory tract inflammation adversely affects how calves respond to subsequent natural infection with M bovis and other respiratory pathogens.

Arrival cortisol measurement in veal calves and its association with body weight, protein fractions, animal health and performance

Male dairy calves are exposed to an accumulation of transport, social and environmental stressors while transferred to fattening units. As a consequence, calves show high cortisol concentrations upon arrival at the veal facility. Whether cortisol levels as measured on arrival can be associated with animal health, welfare and production results is currently unknown. The first objective of this prospective cohort study was to determine possible associations of arrival serum cortisol concentration with health and production variables of veal calves and other arrival predictors like body weight and γ-globulin concentration. The second aim was to investigate potential clustering of arrival risk factors in veal calves for developing bovine respiratory disease (BRD) based on arrival body weight, serum cortisol concentration, total protein and protein fractions. In total, 105 male Holstein calves from two consecutive production cycles in a single, commercial white veal farm were blood sampled directly at arrival on the farm to determine serum cortisol, total protein and protein fractions. All calves were weighed the day after arrival and clinical signs, average daily weight gain (ADG) and carcass weight were collected. Also, all calves of both production cohorts were repeatedly examined by thoracic ultrasonography at the onset of group respiratory disease symptoms (2-3 weeks after arrival) and four weeks later. Linear and logistic mixed models together with k-means clustering were used for statistical analyses. Calves showed on average high, but individually variable serum cortisol concentrations (mean value = 96.6 ng/mL ± standard deviation (SD) = 48.8; Range (R) = 50.0-317 ng/mL). Arrival cortisol, body weight and γ-globulin content were not significantly associated. Serum cortisol and albumin concentrations at arrival were associated with chronic, unresponsive pneumonia. For each increase of serum cortisol concentration by 10 ng/mL, the odds for lung consolidation of ≥1 cm in depth at the second ultrasonography increased, odds ratio (OR) = 1.03 (95 % confidence interval (CI) = 1.01-1.06; P < 0.050). For every decrease in serum albumin concentration by 1g/L, the OR for developing pneumonia was 1.23 (95 % CI= 1.04-1.46; P < 0.015). Additionally, two clusters of calves were identified based upon arrival status: a low risk cluster with below average stress-induced cortisol values, above average body weight, no acute phase response (APR) and no failure of passive immune transfer (FPIT), and a high risk cluster with above average cortisol values, below average body weight, APR and FPIT. High risk calves had higher odds for developing clinical BRD (OR= 3.88 (95 % CI=1.20-12.53; P < 0.020)) and lung consolidation ≥1 cm in depth at week 6-7 after arrival (OR= 3.93 (95 % CI=1.34-11.53; P < 0.013)). Avoiding high cortisol levels upon arrival of calves is important for animal welfare, but also for reduction of the prevalence of chronic, unresponsive pneumonia and the associated need for (repeated) antimicrobial treatment and production losses.

Short communication: Associations of serum biomarkers of stress and inflammation measured at arrival with health, mortality, and growth of calves transported within the first 4 days of life

The objective of this study was to assess the association between serum concentrations of haptoglobin (Hp), cortisol, and l-lactate following transport of dairy heifer calves within their first week of life with health, mortality, and growth during the preweaning period. Blood samples were collected at arrival and included a cohort of 168 Jersey and Jersey-cross calves from 8 different sources located in Minnesota. All calves were raised at a single facility in New Mexico. Incidence of respiratory disease (BRD) and mortality during the preweaning period (60 d of life) were extracted from the farm's software database. Individual body weight was measured at birth and at weaning to estimate average daily gain. No simple linear correlations were found between the biomarkers. The incidence of BRD during the preweaning period was 7.7%. While cortisol and l-lactate serum concentrations were not associated with BRD, Hp was negatively associated with BRD. Receiving operating characteristic curve analysis was performed to determine the optimal threshold value for Hp [threshold ≤0.63 μmol/L (63 μg/mL), area under the curve = 0.65]. A Cox's proportional hazards model revealed that calves with Hp concentration ≤0.63 μmol/L were more likely to be diagnosed with BRD (hazard ratio = 5.0, 95% confidence interval = 1.3-19.0). A mixed linear model showed that calves with Hp concentration ≤0.63 μmol/L tended to have lower average daily gain (454.4 vs. 479.9 g/d) during the preweaning period than calves with Hp >0.63 μmol/L at arrival. Overall mortality of the cohort was 3.5%, and Hp was not associated with mortality. Although circulating concentrations of l-lactate and cortisol measured at arrival were not associated with BRD incidence during the preweaning period of heifer calves transported within the first 4 d of life, calves with serum Hp concentration >0.63 μmol/L were less likely to be diagnosed with BRD and tended to grow more than calves with Hp ≤0.63 μmol/L. Further research is needed to replicate these results in a larger cohort and to better understand the possible influence of greater inflammatory status at arrival on health and growth of calves transported to a calf-raising facility.

Administering an Appeasing Substance to Gir × Holstein Female Dairy Calves on Pre-Weaning Performance and Disease Incidence

(1) Background: Ruminants often face stressful situations throughout their productive lives. More specifically, pre-weaning dairy calves are exposed to novel environments, feedstuffs, and pathogens that affect their health and performance. Hence, alternatives that reduce stress and promote growth of pre-weaning dairy calves are warranted. Therefore, this study evaluated the effects of biweekly bovine appeasing substance (BAS) administration on performance and disease incidence in dairy Gir × Holstein female calves prior to weaning. (2) Methods: At birth, 140 female Gir × Holstein calves were randomly assigned to receive BAS (SecureCattle; (IRSEA Group, Quartier Salignan, France; n = 70) or placebo (BAS carrier, diethylene glycol monoethyl ether; CON; n = 70) biweekly until weaning (70 days of age). Calves were allocated into individual housing at random, with no physical contact between treatments to avoid cross-contamination. Experimental treatments (5 mL) were applied topically to the nuchal skin area of each calf. Throughout the experimental period, all animals were observed daily for medical conditions (diarrhea, pneumonia, and others), medical/pharmacological interventions were recorded, and the costs related to these procedures were analyzed. Concurrently with treatment application, calves were individually weighed, and data were analyzed using animal as the experimental unit. (3) Results: Treatment × day and treatment × period (14-day interval) interactions were observed for body weight (BW) and average daily gain (ADG; p ≤ 0.05), respectively. Calves receiving BAS had greater BW at weaning (p = 0.02) and tended to have a greater BW on day 56 (p = 0.06). Similarly, ADG was greater for BAS from days 42 to 56 (p = 0.04) and tended to be greater from days 56 to weaning (p = 0.10). No differences were observed on the overall occurrence of diseases (p = 0.92), whereas the most common observed diseases were diarrhea and pneumonia. The incidence and mean age at which animals were detected with these diseases did not differ (p ≥ 0.46). Nonetheless, CON calves detected with disease had a reduced ADG vs. BAS-administered counterparts (p < 0.01). No differences were observed between disease-diagnosed BAS vs. healthy CON, but healthy BAS had a greater ADG vs. healthy CON (p = 0.03). A treatment effect was observed for the cost per head of each pharmacological intervention (p = 0.05). (4) Conclusions: In summary, BAS administration at a 14-day interval improved performance and reduced the costs of pharmacological interventions of pre-weaning Gir × Holstein dairy calves.

Effects of the Administration of a Non-specific Immune Stimulant Around Transportation on Health and Performance of Jersey and Jersey-Cross Heifer Calves During the Rearing Period: Randomized Clinical Trial

Our objective was to evaluate the effects of a non-specific immune stimulant (IS) administered around transportation on health scores (HS), average daily gain (ADG), disease treatment and mortality of Jersey and Jersey-cross calves during the rearing period. Newborn calves (4 d ± 1) were randomly allocated to receive either 1 mL of saline (CON; n = 438), 1 mL of IS before transport (BTIS; n = 431), or 1 mL of IS immediately after transport (ATIS; n = 436). Calves were health scored weekly for 3 weeks after transport. The data were analyzed using multivariable linear mixed models and multivariable logistic regression models. Kaplan-Meier survival analysis was performed for time to event analysis. Treatment, birth weight, breed, site of birth, serum total solids, dam parity, season of enrollment, and metaphylaxis were offered to models. Differences in respiratory and fecal HS, and ADG between treatment groups were not statistically significant. A total of 196 (15.0%) calves were treated at least once for any disease and 52 calves were treated multiple times. The proportion of calves treated for respiratory disease and/or diarrhea were 14.4, 14.4, and 16.2% for BTIS, ATIS and CON groups, respectively. Although the differences in the likelihood of treatment for both respiratory disease and/or diarrhea during the first 9 weeks of life was not statistically different between groups, we observed that more calves in the control group received disease treatments around 15 days of age compared with calves that received IS. The likelihood of treatment for respiratory diseases alone during the first 30 days of life was smaller in the calves that received IS before transportation when compared to the control group. Only 18 (1.4%) calves died within the study period. The calf mortality likelihood was not statistically different between study groups; however, fewer calves in the IS groups died when compared to CON. In conclusion, the use of IS around transportation did not influence weekly HS, ADG, and the number of disease treatments during the rearing period, but administering IS before transportation resulted in fewer treatments of respiratory diseases during the first 30 days post-transport and marginally lower mortality rates during the rearing period.

Effects of omega-3 fatty acids on immune, health and growth variables in veal calves

Under the present intensive rearing conditions, calves face a series of stressors and multiple pathogens often necessitating antimicrobial use. Multiple feed additives are currently explored for their ability to prevent disease and limit the use of antimicrobials. Supplementation of the polyunsaturated long chain n-3 fatty acids eicosapentaenoic (EPA) and docohexaenoic (DHA) from marine origin has been proposed as a strategy to improve immune function and prevent excessive inflammation reactions. The aim of this randomized clinical trial was to explore the effects of n-3 fatty acids (PUFAs) used as feed supplement on health, production and immune variables in a veal calf setting. One hundred-seventy calves were randomly assigned to 3 treatment groups: microalgae (MA, n = 57, 2.5 g DHA/animal/day), fish oil (FO, n = 57, 2.5 g EPA + DHA/animal/day)] and a control group (CON, n = 56). Average daily gain (ADG), bodyweight at 12 weeks on feed and slaughter weight were determined. Health monitoring consisted of recording of clinical signs and repeated thoracic ultrasonography. After 5, 8 and 11 weeks of supplementation, the function of neutrophils, monocytes and peripheral blood mononuclear cells (PBMCs) was evaluated ex vivo by measuring reactive oxygen species (ROS) production by neutrophils and monocytes and proliferation of and cytokine release by PBMCs. Under the field conditions of this study, dietary supplementation of MA and FO showed very limited immunomodulatory effects. Feeding MA led to increased ROS production by neutrophils, Estimate (E) = 0.38, Standard Error (SE) = 0.14; P < 0.05, compared to the control calves after 5 weeks of in-feed supplementation. FO reduced IL-6 secretion E= -0.29, SE= 0.11; P < 0.05 compared to MA treated animals after 11 weeks on feed. Health and production variables were unaffected by treatments. The doses of EPA and DHA used in this study did not cause immunomodulatory changes in highly stressed calves to such an extent that this led to better health or growth of animals.

Effects of glycerol-esters of saturated short- and medium chain fatty acids on immune, health and growth variables in veal calves

In veal and dairy beef production systems, Holstein bull calves experience many stressors and excessive pathogen exposure, necessitating the use of antimicrobials for welfare and production reasons. The aim of this randomized clinical trial was to explore the effects of esterified fatty acids used as feed supplement on health, production and immune variables in veal calves. Different glycerol-esters of fatty acids were used: short chain fatty acid (SCFA)-based glycerol-mono- (C4) and tributyrate (C4), and medium chain fatty acid (MCFA)-based glycerol-monocaprylate/monocaprinate (C8/C10) and glycerol-monolaurate (C12) in two different doses. One hundred sixty eight calves (2-to 4-week-old) were randomly assigned to 6 treatment groups; tributyrate (0.5 g/animal/day); monobutyrate (1 g/animal/day); low C8/C10 (7 g/animal/day) and high C8/C10 (10 g/animal/day); low C12 (4 g/animal/day) and high C12 (6 g/animal/day) and a control group (CON). Duration of in-feed supplementation was 14 weeks. Average daily gain, bodyweight at 14 weeks on feed and slaughter weight were determined. Health monitoring consisted of clinical signs and repeated thoracic ultrasonography. After 4, 8 and 12 weeks of supplementation, the function of neutrophils, monocytes and peripheral blood mononuclear cells (PBMCs) was evaluated ex vivo by measuring reactive oxygen species (ROS) production by neutrophils and monocytes, proliferation of and cytokine release by PBMCs. Study power was based upon ROS production by neutrophils and treatment groups were too limited to detect significant differences in growth and health variables. Glycerol-ester supplementation resulted in different effects on immune cell function, depending on the type and dose of the glycerol-ester as well as duration of supplementation. Our main findings were increased secretion of interleukin IL-17A by PBMCs at 4 weeks of feed supplementation in high C8/C10 (P< 0.01), low C12 (P < 0.01) and monobutyrate (P< 0.01) groups, combined with decreased ROS production in neutrophils (P < 0.001) and monocytes (P < 0.05) in the high C8/C10 and monocytes (P < 0.05) in low C12 groups compared to the control animals. After 12 weeks on feed, ROS production by neutrophils (P < 0.001) and monocytes (P < 0.01) of monobutyrate and by monocytes (P < 0.01) of tributyrate groups was decreased compared to control calves. In summary, supplementation of glycerol-esters of MCFAs resulted in immune-modulatory effects, which did not manifest themselves in improved health and growth of calves under the conditions and limitations of this study. Especially doses of high C8/C10 and low C12 show potential to promote an early, robust pro-inflammatory response with diminished ROS production. This might be beneficial for clearance of pathogens in young calves in periods of stress and high pathogen load.

Effects of the novel concept 'outdoor veal calf' on antimicrobial use, mortality and weight gain in Switzerland

The aim of the intervention study 'outdoor veal calf' was to evaluate a novel concept for calf fattening which aimed at reducing antimicrobial use without compromising animal health. Management practices such as commingling of calves from multiple birth farms, crowding, and suboptimal barn climate are responsible for high antimicrobial use and mortality in the veal calf population. The risk of selecting bacteria resistant to antimicrobials and of economic losses is accordingly elevated. The 'outdoor veal calf' concept, implemented in nineteen intervention farms (IF), is based on three main measures: 1. purchased calves are transported directly from neighboring birth farms to the fattening facility instead of commingling calves in livestock dealer trucks; 2. each calf is vaccinated against pneumonia after arrival and completes a three-week quarantine in an individual hutch; and 3. the calves spend the rest of the fattening period in outdoor hutches in groups not exceeding 10 calves. The covered and bedded paddock and the group hutches provide shelter from cold weather and direct sunshine, constant access to fresh air is warranted. Nineteen conventional calf fattening operations of similar size served as controls (CF). Every farm was visited once a month for a one-year period, and data regarding animal health, treatments, and production parameters were collected. Treatment intensity was assessed by use of the defined daily dose method (TI_DDD in days per animal year), and calf mortality and daily weight gain were recorded in both farm groups. Mean TI_DDD was 5.3-fold lower in IF compared to CF (5.9 ± 6.5 vs. 31.5 ± 27.4 days per animal year; p < 0.001). Mortality was 2.1-fold lower in IF than in CF (3.1% ± 2.3 vs. 6.3 % ± 4.9; p = 0.020). Average daily gain did not differ between groups (1.29 ± 0.17 kg/day in IF vs. 1.35 ± 0.16 kg/day in CF; p = 0.244). A drastic reduction in antimicrobial use and mortality was achieved in the novel 'outdoor veal calf' system without compromising animal health. The principles of risk reduction used in designing the system can be used to improve management and animal health, decrease the need for antimicrobial treatments and thus selection pressure on bacteria in veal operations.

Validation of serum gamma-glutamyl transferase activity and body weight information for identifying dairy calves that are too young to be transported to auction markets in Canada

Dairy calves are at risk of being stressed when transported during the first week of life. A new Canadian federal rule will forbid transportation of calves younger than 9 d old to auction market. However, in the absence of reliable information to determine birth date, other indirect methods would be of interest. This study aimed to determine the prediction accuracy of body weight, Brix refractometry, and serum gamma-glutamyl transferase (GGT) activity for determining if a calf was not fit to be transported (i.e., <9 d old). For this purpose, we used 284 calves with a known birth date from a cross-sectional and a prospective cohort study. A logistic regression model was built based on multivariable analysis as well as a misclassification cost term analysis. Because of the collinearity between GGT activity and Brix value and lower discrimination of Brix value, the GGT activity was retained for the main model. The final logistic regression model contained body weight and log-transformed GGT activity value. The misclassifications of the logistic model was minimized using a model probability threshold ≥0.55 with a sensitivity of 70.4% and a specificity of 77.3%. This probability threshold was relatively robust for various prevalence and false negative to false positive cost ratios. The prediction accuracy of this model was moderate at the individual level, but is helpful in calves with a reasonable suspicion of being less than 9 d old.

Short communication: Risk factors identified at arrival associated with average daily gain at a grain-fed veal facility: A prospective single cohort study

The primary objective of this prospective cohort study was to identify factors evaluated upon arrival at a grain-fed veal facility that were associated with increased growth. A secondary objective was to determine if the factors associated with average daily gain (ADG) varied between the pre- and postweaning periods. Calves were visually assessed and scored using a standardized health scoring system immediately upon arrival. They were also weighed and vaccinated, and had blood drawn from their jugular vein to determine their serum total protein level. Weights were taken on d 49 and 78 after arrival and were used to calculate ADG. Three mixed linear regression models were created to determine factors associated with ADG from 0 to 49 d after arrival, 0 to 78 d after arrival, and 49 to 78 d after arrival. A total of 998 calves were evaluated and weighed upon arrival; 636 and 915 of those calves were weighed at d 49 and d 78, respectively. Mean ADG were 610 g/d from 0 to 49 d after arrival, 860 g/d from 0 to 78 d after arrival, and 1,240 g/d from 49 to 78 d after arrival. In the model evaluating growth from 0 to 49 d, calves arriving at the facility with a higher body mass index (BMI) gained more weight per day than calves that arrived with a lower BMI. If calves arrived in the spring, they gained 201 g/d more than calves that arrived in the winter. For the period following weaning (d 49 to 78), BMI was also associated with growth. For every additional 1 g/cm² increase in BMI at arrival, calves gained an additional 1.55 g/d from d 49 to 78. Growth from arrival to d 78 was affected solely by BMI. For every 1 g/cm² increase in BMI at arrival, calves gained 1.23 g/d more during the entire observation period. Body mass index and season at arrival affected growth through the initial period at a grain-fed veal facility. Producers should consider these factors, especially BMI, when purchasing calves to maximize the calves' growth potential.

Risk factors identified on arrival associated with morbidity and mortality at a grain-fed veal facility: A prospective, single-cohort study

High levels of morbidity, mortality, and antimicrobial use are common in the veal industry. For the sustainability of the industry, it is important to address these challenges and determine factors that can be used to improve animal health and welfare. The objectives of this prospective observational cohort study were to describe the health status of calves on arrival at a grain-fed veal facility and determine characteristics that were associated with morbidity and mortality. On arrival, the calves were assessed for health abnormalities, weighed, measured for hip height and length from withers to lumbosacral junction, and had blood collected to determine serum total protein level. Body mass index (BMI) was calculated using weight on arrival divided by the sum of the calf's length from withers to lumbosacral junction and hip height. The calves were observed for 77 d after arrival, during which the producer was responsible for recording all antibiotic treatments and mortality. We built Cox proportional hazard models for morbidity and mortality variables. We created 2 morbidity models: 1 for calves that were treated <21 d after arrival at the facility, and 1 for calves that were treated during the 11 wk at the facility. From January to December 2017, 998 calves were evaluated on arrival at the veal rearing facility. A large proportion (68%) were treated with antibiotics in the first 21 d after arrival. The only explanatory variable in the final <21 d morbidity model was BMI: calves with a higher BMI had a lower hazard of being treated for disease in the first 21 d after arrival. A total of 872 calves (87%) were treated at least once over the 11-wk housing period. A calf arriving with a BMI >371.46 g/cm or a serum total protein between 5.8 and 6.2 g/dL had a lower level of morbidity during the observation period. Over the 11-wk housing period, 74 calves (7.5%) died. Calves that arrived at the facility with a fecal score of 2 or a rectal temperature between 38.9 and 39.1°C had a higher hazard of dying; calves that had a BMI of >371 g/cm were less likely to die than calves that had a BMI <330 g/cm. These results point to the importance of assessing calves on arrival at a veal facility as a measure of identifying those at high risk for morbidity and mortality.

Randomized field trial on the effects of body weight and short transport on stress and immune variables in 2- to 4-week-old dairy calves

Background

Whether underweight calves respond differently to transport stress, enhancing their disease risk, is currently unknown.

Objective

To determine the effects of low body weight and transport stress on immune variables.

Animals

Twenty‐one 2‐ to 4‐week‐old male Holstein calves, housed on a commercial farm.

Methods

Randomized clinical trial. Full factorial design with 4 treatment groups: low body weight (≤46 kg)/no transport (LOWCON); low body weight/transport (LOWTRANS); normal body weight (>46 kg)/no transport (NORMCON), and normal body weight/transport (NORMTRANS). Transport duration was 2 hours.

Results

Transport significantly increased serum cortisol concentration (77.8 μg/mL; 95% confidence interval [CI], 37.8‐131.6; P < .001), interleukin (IL)‐17A (344.9 pg/mL; 95% CI, 32.2‐556.5; P = .04), and tumor necrosis factor‐α (TNF‐α) (218.2 pg/mL; 95% CI, 32.5‐368.3; P = .03) production after lipopolysaccharide (LPS) stimulation. Body weight did not affect any of the studied variables. However, the interaction of transport and body weight was significant. LOWTRANS calves showed increased monocyte count (2.0 × 10⁹/L; 95% CI, 0.6‐4.2; P < .05) and interleukin IL‐17A production (106.0 pg/mL; 95% CI, 4.2‐306.9; P = .03) compared to normal weight calves and increased TNF‐α production (275.6 pg/mL; 95% CI, 2.6‐463.0; P = .02) compared to LOWCON calves in unstimulated peripheral blood mononuclear cells (PBMCs) after transport.

Conclusion and Clinical Importance

These findings contribute to our understanding of increased disease susceptibility of underweight calves when transported. Gamma globulin concentration was identified as important interfering factor in studies on immune variables in neonatal calves.