Prevalence of respiratory disorders in veal calves and potential risk factors

Effects of nondigestible oligosaccharides on inflammation, lung health, and performance of calves

Our objective was to determine the effects of nondigestible oligosaccharides (NDO) on lung health and performance. Three hundred male Holstein-Friesian calves aged 18.0 ± 3.6 d received 1 of 6 treatments for 8.5 wk (period 1). Treatments included a negative control (CON), galacto-oligosaccharides (GOS) administered as a spray via the nose once daily (SPR), GOS administered via the milk replacer (MR) at 1% (GOS-L) and 2% (GOS-H), fructo-oligosaccharides administered via the MR at 0.25% (FOS) and a combination of GOS and fructo-oligosaccharides administered via the MR at 1% and 0.25%, respectively (GOS-FOS). Milk replacer was fed twice daily. Feeding levels were equal between calves and increased progressively in time. Body weight was measured every 4 wk and clinical health was scored weekly. Blood and broncho-alveolar lavage fluid (BALF) samples were collected bi-weekly from a subset of calves (n = 120). After period 1, all calves received the same control MR for 18 wk until slaughter (period 2), during which general performance and clinical health were measured. Generally, infection pressure was high, with clinical scores and BALF proinflammatory TNFα concentrations increasing with time in period 1, which resulted in a high number of required group antimicrobial treatments (6 group antimicrobial treatments in 13 wk, supplied to all calves). Average daily gain adjusted to equal solid feed intake was increased for GOS-L (+61 g/d) compared with CON calves from experimental wk 1 to 5. Plasma white blood cell concentration tended to be lowered by GOS-L, plasma IL-8 concentration was reduced by all orally supplemented NDO, plasma IL-6 was reduced by all NDO treatments except GOS-FOS and plasma IL-1β was reduced by all NDO treatments compared with CON, although this differed per time point for SPR. The neutrophil percentage in BALF was reduced by GOS-L in wk 6, which was associated with a relative increase in macrophages. The BALF concentration of TNFα and IL-8 was reduced or tended to be reduced by GOS-L and GOS-H, while IL-6 was or tended to be reduced by SPR, GOS-L, GOS-H, and GOS-FOS, and IL-1β was reduced by SPR, GOS-L, GOS-H, and FOS. Generally, feeding the combination of GOS and FOS was not more effective than feeding GOS or FOS alone, because feeding GOS-FOS resulted in higher concentrations of plasma and BALF cytokine and chemokine concentrations compared with feeding GOS-L alone, and resulted in higher plasma cytokine concentrations compared with feeding FOS alone. None of the BALF and plasma cytokine or chemokine concentrations differed between the GOS-L and GOS-H treatment. Performance and clinical scores in period 2 did not differ among treatments. Altogether, all tested NDO reduced systemic and lung inflammation in calves under high natural infection pressure and for GOS-fed calves, this increased performance during the first 4 wk. Combining GOS and FOS did not have a synergistic effect. The intranasal administration of GOS also lowered systemic and lung inflammation, but tended to negatively affect performance. Overall, this study demonstrates the potential of NDO to alleviate systemic and respiratory inflammation in calves.

Veal calves management in Québec, Canada: Part I. Association between passive immunity transfer at arrival and health disorders

Morbidity and mortality remain important concerns for veal production which traditionally involves very young calves being transported directly from dairy farms to calf-raising facilities or sold through auction markets from dairy farms. There are few studies that examine the relationship between transfer of passive immunity and health outcomes in veal production in Québec. The objective of this study was to investigate the risk factors associated with morbidity and mortality in milk and grain-fed veal facilities in Québec. Between October 2017 and December 2018, a prospective cohort study was conducted on 59 batches of milk- and grain-fed veal calves from Montérégie and Centre du Québec regions in Québec, Canada. A total of 30 calves per batch were randomly sampled for the transfer of passive immunity (TPI) status using the Brix refractometer (serum threshold ≥ 8.4%). Throughout the production cycle, arrival, treatment, mortality, and slaughter records of each batch of calves were extracted and used to quantify individual- and group-level risk factors. Morbidity and mortality were modelled through generalized linear mixed models (GLMMs) using a logit link, as function of categorical variables (individual inadequate TPI, arrival season, purchasing sites, and arrival weights) and a continuous variable (proportion of inadequate TPI in the batch). Given that the health and performance data are usually collected retrospectively under commercial settings, incomplete data was recognized as a potential issue. Thus, multiple imputation models were used. From 59 batches where 1729 calves were sampled for measuring TPI, 1084 calves had a serum Brix% < 8.4% giving a prevalence of 62.7% of inadequate TPI. The prevalence of morbidity and mortality in those 59 batches were not associated with the batch-level inadequate TPI prevalence. On the other hand, individual calves with inadequate TPI had higher odds of morbidity (OR: 1.56; 95% CI: 1.2-2.05, P = 0.001) compared to those calves with adequate TPI. Odds of mortality, on the other hand, were not significantly affected by inadequate TPI (OR:1.27; 95% CI: 0.74-2.18, P = 0.3). Calves arriving to the facility during the winter season had lower odds of mortality than those arriving in fall (OR:0.16; 95% CI: 0.03-0.78, P = 0.02). In conclusion, this study suggests that inadequate TPI, as assessed upon arrival in veal farms, remains an important concern for negative health outcomes in veal calves.

Strategies for Bovine Respiratory Disease (BRD) Diagnosis and Prognosis: A Comprehensive Overview

Despite significant advances in vaccination strategies and antibiotic therapy, bovine respiratory disease (BRD) continues to be the leading disease affecting the global cattle industry. The etiology of BRD is complex, often involving multiple microbial agents, which lead to intricate interactions between the host immune system and pathogens during various beef production stages. These interactions present environmental, social, and geographical challenges. Accurate diagnosis is essential for effective disease management. Nevertheless, correct identification of BRD cases remains a daunting challenge for animal health technicians in feedlots. In response to current regulations, there is a growing interest in refining clinical diagnoses of BRD to curb the overuse of antimicrobials. This shift marks a pivotal first step toward establishing a structured diagnostic framework for this disease. This review article provides an update on recent developments and future perspectives in clinical diagnostics and prognostic techniques for BRD, assessing their benefits and limitations. The methods discussed include the evaluation of clinical signs and animal behavior, biomarker analysis, molecular diagnostics, ultrasound imaging, and prognostic modeling. While some techniques show promise as standalone diagnostics, it is likely that a multifaceted approach-leveraging a combination of these methods-will yield the most accurate diagnosis of BRD.

Literature Review of the Principal Diagnostic Tests to Detect Bovine Respiratory Disease in Pre-Weaned Dairy and Veal Calves

Bovine respiratory disease (BRD) is an infection of the upper and lower respiratory tract, characterized by an inflammation of the lung. Different diagnostic tests can be used to detect BRD, including clinical respiratory scoring systems, thoracic auscultation, and imaging tests like thoracic ultrasonography and thoracic radiography. Although commonly used, none of these diagnostic tests are perfect for detecting BRD. This article reviews the advantages and drawbacks of these techniques and their performance in detecting BRD in pre-weaned dairy and veal calves.

Diagnostic and Prognostic Value of Clinical Scoring and Lung Ultrasonography to Assess Pulmonary Lesions in Veal Calves

This study on veal calf respiratory disease assessed the association between an on-farm clinical scoring system and lung ultrasonography with the postmortem inspection of the lungs. The comparisons allowed the calculation of predictive values of the diagnostic methods. In total, 600 calves on an Austrian veal calf farm were examined at the beginning and the end of the fattening period. Overall, the area under the curve (AUC) for ultrasonographic scores was 0.90 (rsp = 0.78) with a sensitivity (Se) of 0.86. The specificity (Sp) was 0.78, and the positive predictive value (PPV) was 0.74. The AUC for the physical examination was 0.76 (rsp = 0.55) with a Se of 0.64, an Sp of 0.81, and a PPV of 0.69. For the combination of ultrasonography and physical examination, an AUC curve of 0.85 (rsp = 0.69) was calculated. A Se of 0.65 and a Sp of 0.88 with a PPV of 0.73 was calculated. This study concluded that both physical and ultrasonographic examination scoring are reliable examination methods for the detection of lung diseases in veal calves.

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.

Developing a tool to assess the health-related quality of life in calves with respiratory disease: content validation

Bovine respiratory disease (BRD) is a major welfare and productivity issue for calves. Despite the extensive negative impacts on calf welfare and performance, BRD remains challenging to detect and treat effectively. However, the clinical signs of disease are only one aspect of the disease that is experienced by the individual. The assessment of emotional experience in animals is not straightforward, but it is increasingly recognised that the quality of behaviour and demeanour of an individual is a reflection of their internal emotional state. The aim of the present study was to complete the content validation stage of the development process for a health-related quality of life (HRQOL) tool. This was based around indicators from an existing conceptual framework containing twenty-three indicators in two domains (clinical signs and behavioural expression). The content validation stage involves engaging with key stakeholders. For this study, this took the form of a survey and discussions with focus groups, which are standard methods in this field. A survey and stakeholder focus groups were conducted to assess the usefulness of each indicator and its relevance for inclusion within a HRQOL tool. In the survey, participants were asked to rate the usefulness of each of the indicators using a 4-point scale which were then dichotomised into 'useful' and 'less useful'. Based on the 'useful' result, each indicator within the domains was ranked. A similar approach was taken with the responses from the focus groups. Focus group participants were asked to select indicators that they felt were of use and the result of this was used to rank each of the indicators. The ranks of the indicators from both the survey and the focus groups along with the transcripts from the focus groups were used to determine the indicators from each domain to include within the HRQOL tool. Indicators within the clinical signs domain that were included were nasal discharge, cough, respiratory effort, ocular appearance (discharge and vibrancy), body and head posture and ear carriage. For the domain of behavioural expression, the indicators included were movement to feed, responsiveness, spatial proximity, volume of feed intake, motivation at feed and vigour. The next stage will be to validate the construction of the HRQOL tool through its use in practice. The inclusion of indicators that allow the experiential aspects of disease to be recorded in health assessments will likely increase the ability of farmers and others to detect respiratory disease in calves.

Impact of early dam contact on veal calf welfare

Dairy calves, including surplus calves, are typically separated from their dam within hours of birth. The aim of this study was to assess the welfare impacts of raising surplus calves destined for veal with their dam for 2 or 4 weeks until transport. Surplus calves from one dairy farm were separated from their dam at birth (n = 39) or kept with the dam (n = 37) until transport to the veal farm at either 2 (n = 50) or 4 (n = 26) weeks of age, with abrupt separation for dam-reared calves. Calf measures of body weight, health, immunity, haematology and behaviour were recorded at the dairy and veal farms. Dam-reared calves had higher body weights in weeks 3, 4 and 5 at the DF, as well as at arrival at the veal farm, but by slaughter this advantage was lost. More dam-reared calves had fever in week 3 and showed signs of disease in week 5 at the dairy farm. Dam-reared calves did not differ in IgG, IgA or IgM levels but had higher counts of white blood cells, which could reflect a higher pathogen exposure rather than improved immunity. Dam-reared calves displayed more fear towards humans in a human approach test at 5 and 7 weeks after arrival at the veal farm, and more frequent social behaviours at the veal farm at 9 and 16 weeks of age. In conclusion, it seems that there may be both advantages and disadvantages to keeping veal calves with the dam in terms of welfare in the current system.

Journeys, Journey Conditions, and Welfare Assessment of Broken (Handled) Horses on Arrival at Italian Slaughterhouses

During horse transportation, the journey conditions are considered a welfare risk. This study aimed to document journeys, journey conditions, and welfare status of handled horses on arrival at two different slaughterhouses in Northern and Southern Italy, to find possible associations between journey conditions and welfare problems. The welfare status of 613 draft-breed and light-breed horses from 32 different journeys was evaluated on arrival at the slaughterhouses with a standardized protocol, using animal-based (ABMs) and environmental-based (EBMs) measures. The drivers’ skills and vehicle characteristics were found to be mostly compliant with EC 1/2005. The horses traveled in single bays, 90° to the direction of travel for an average journey duration of 26.5 ± 14 h. On arrival at the slaughterhouses, the horses were unloaded by handlers, via halter and rope. The prevalence of reluctance to unload, injuries, nasal, and lacrimal discharge was 22.2%, 24.6%, 11.6%, and 10%, respectively. Journey duration, unloading duration, vehicle changes, long stops, handlers/drivers’ skills, temperature, season, and horse individual characteristics were associated with horses’ welfare and health status (all p < 0.05). Our study confirms the hypothesis that appropriate journey conditions are of crucial importance to safeguard the welfare of broken/handled horses transported over long distances for slaughter.

Individual antimicrobial treatments in veal calves: Effect on the net carcasses weight at the slaughterhouse and relationship with the serostatus of the calves upon arrival to the fattening unit

In recent years, the scientific community, institutions, and public opinion have shown a growing awareness towards the problem of antimicrobial resistance. Guidelines from the European Union aim at significantly reducing (even avoiding) the antimicrobial use for prophylactic and metaphylactic purposes in veterinary medicine and this represents an important issue for several intensive farming systems, such as the veal industry. This retrospective observational cohort study analyzed net carcass weight data at the slaughter of 618 veal calves belonging to 6 batches of animals fattened in an Italian commercial farm according to the number of individual antimicrobial treatments administered during the fattening cycle. Sixty-eight percent (419 animals) of the overall sample of calves received at least one individual antimicrobial treatment due to a disease event during the fattening, and 280 of these (45 % of the overall sample) had more than one treatment. On average, the net carcass weight of calves individually treated more than once was about 10 kg lower than that of untreated calves or treated only once. Moreover, the carcasses of calves that received more than one treatment were 16 times more at risk of being severely penalized in payment at the slaughterhouse due to a net weight below 110 kg than those of untreated calves. Serum analysis data of a subsample of 105 calves belonging to 3 out of the 6 batches collected within 5 days after their arrival to the veal farm identified 3 persistently infected animals by bovine viral diarrhea (BVD) virus and a prevalence of calves with serum immunoglobulin concentration below 7.5 g/L of 37 %. The presence of specific antibodies against infectious bovine rhinotracheitis (IBR) and bovine respiratory syncytial virus (BRSV) and a serum immunoglobulin level above 7.5 g/L at the onset of the fattening were the most important factors associated with a decreased risk of multiple individual antimicrobial treatments (and thus, disease development) or with a delay in disease onset during the fattening, thus leading to better performances at the slaughter. The outcomes of this study suggested that a relationship could exist between calf serostatus upon arrival to the veal farm and the possibility to avoid multiple individual antimicrobial treatments during fattening. Further research is needed to deeply study this association, as such knowledge would allow for planning effective preventing strategies to reduce the antimicrobial use in veal calves.

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.

Antimicrobial Use and Resistance in Surplus Dairy Calf Production Systems

Surplus calves, which consist predominately of male calves born on dairy farms, are an underrecognized source of antimicrobial-resistant (AMR) pathogens. Current production systems for surplus calves have important risk factors for the dissemination of pathogens, including the high degree of commingling during auction and transportation and sometimes inadequate care early in life. These circumstances contribute to an increased risk of respiratory and other infectious diseases, resulting in higher antimicrobial use (AMU) and the development of AMR. Several studies have shown that surplus calves harbor AMR genes and pathogens that are resistant to critically important antimicrobials. This is a potential concern as the resistant pathogens and genes can be shared between animal, human and environmental microbiomes. Although knowledge of AMU and AMR has grown substantially in dairy and beef cattle systems, comparable studies in surplus calves have been mostly neglected in North America. Therefore, the overall goal of this narrative review is to summarize the existing literature regarding AMU and AMR in surplus dairy calf production, highlight the management practices contributing to the increased AMU and the resulting AMR, and discuss potential strategies and barriers for improved antimicrobial stewardship in surplus calf production systems.

Direct genetic effects, maternal genetic effects, and maternal genetic sensitivity on prenatal heat stress for calf diseases and corresponding genomic loci in German Holsteins

The aim of this study was to infer the effects of heat stress (HS) of dams during late gestation on direct and maternal genetic parameters for pneumonia (PNEU, 112,563 observations), diarrhea (DIAR, 176,904 observations), and omphalitis (OMPH, 176,872 observations) in Holstein calves kept in large-scale co-operator herds. The genotype dataset included 41,135 SNPs from 19,247 male and female cattle. Temperature-humidity indices (THI) during the last 8 wk of pregnancy were calculated, using the climate data from the nearest public weather station for each herd. Heat load effects were considered for average weekly THI larger than 60. Phenotypically, regression coefficients of calf diseases on prenatal THI during the last 8 wk of gestation were estimated in 8 consecutive runs. The strongest detrimental effects of prenatal HS on PNEU and DIAR were identified for the last week of pregnancy (wk 1). Thus, only wk 1 was considered in ongoing genetic and genomic analyses. In an advanced model considering prenatal HS, random regression coefficients on THI in wk 1 nested within maternal genetic effects (maternal slope effects for heat load) were considered as parameters to infer maternal sensitivity in response to prenatal THI alterations. Direct heritabilities from the advanced model ranged from 0.10 (THI 60) to 0.08 (THI 74) for PNEU and were close to 0.16 for DIAR. Maternal heritabilities for PNEU increased from 0.03 to 0.10 along the THI gradient. For DIAR, the maternal heritability was largest (0.07) at the minimum THI (THI = 60) and decreased to 0.05 at THI 74. Genetic correlations smaller than 0.80 for PNEU and DIAR recorded at THI 60 with corresponding diseases at THI 74 indicated genotype by climate interactions for maternal genetic effects. Genome-wide associations studies were performed using de-regressed proofs of genotyped sires for direct genetic, maternal genetic, and maternal slope effects. Thirty suggestive and 2 significant SNPs were identified from the GWAS. Forty-three genes located close to the suggestive SNPs (±100 kb) were annotated as potential candidate genes. Three biological processes were inferred on the basis of the these genes, addressing the negative regulation of the viral life cycle, innate immune response, and protein ubiquitination. Hence, the genetics of prenatal heat stress mechanisms are associated with immune physiology and disease resistance mechanisms.

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.

Effect of Farm Management Practices on Morbidity and Antibiotic Usage on Calf Rearing Farms

Antimicrobial resistance has been recognized as one of the top health threats to human society. Abundant use of antibiotics in both humans and animals has led to ever-increasing antibiotic resistance in bacteria. In food production, decreasing morbidity in beef herds would be an effective way to reduce the use of antibiotics. The objective of this retrospective observational study was to determine overall morbidity on calf rearing farms and to identify associated risk factors. Data were collected by questionnaire, meat companies’ databases and the national cattle register for 28,228 calves transported to 87 calf rearing farms. All medications given to these calves were retrospectively followed for 180 days from calf arrival to the farm. In total, 34,532 parenteral antibiotic medications were administered to the 28,228 study calves (122.3%), and 17,180 calves (60.9%) were medicated with antibiotics at least once during the follow-up. Higher numbers of calves transported to the same farm and larger age variation in calves in the same arrival batch were both associated with increased morbidity. In contrast, higher arrival age of individual calves was associated with decreased morbidity. Our study identifies several factors to consider in decreasing morbidity and antibiotic usage on calf rearing farms.

Effects of transport age and calf and maternal characteristics on health and performance of veal calves

The objective of this study was to investigate effects of calf transport age (14 vs. 28 d) and calf (e.g., sex and breed) and dam characteristics (e.g., parity and ease of birth) on health and performance of veal calves until slaughter age. Calves (n = 683) originated from 13 dairy farms in the Netherlands and were transported at either 14 or 28 d of age from the dairy farm to 8 Dutch veal farms. A health assessment of calves was performed on a weekly basis at the dairy farm and in wk 2, 10, 18, and 24 at the veal farm. Body weight of calves was measured on a weekly basis at the dairy farm and upon arrival at the veal farm. At the veal farm, use of antibiotics and other medicines during the rearing period (both at herd and individual level) was recorded and carcass weights were obtained from the slaughterhouse. Body weight upon arrival (Δ = 11.8 kg) and carcass weight at slaughter (Δ = 14.8 kg) were greater, and mortality risk (Δ = -3.1%) and prevalence of animals treated with medicines other than antibiotics (e.g., antiinflammatories, multivitamins, and anticoccidial drugs; Δ = -5.4%) were lower in calves transported at 28 d compared with calves transported at 14 d. Crossbreds other than Belgian Blue × Holstein Friesian received a higher number of individual treatments with antibiotics and other medicines (Δ = 14.8% and Δ = 15.1%, respectively) at the veal farm compared with Belgian Blue × Holstein Friesian calves. These findings suggest that calves transported at 28 d were more robust compared with calves transported at 14 d.

Factors associated with antimicrobial use in pig and veal calf farms in the Netherlands: A multi-method longitudinal data analysis

Minimizing antimicrobial use (AMU) in livestock is needed to control antimicrobial resistance (AMR). In the Netherlands, the livestock sector reduced AMU by almost 70 % since 2009, but this reduction stagnated in recent years. With only therapeutic AMU allowed, it is clear that besides socio-economic and behavioral factors, also the farm technical characteristics influence the conditions under which farmers need AMU. These characteristics pertain to farm management, including biosecurity, vaccination schemes, nutrition, micro-climate and husbandry practices. Identifying farm-related risk factors for AMU is needed to control AMR in a sustainable and pragmatic way. This need, often concerns the overall contribution of seemingly related (rather than individualized) factors. Here, risk factors for AMU in pig and calf farms were determined using two approaches: a typical risk factor analysis based on generalized estimating equations (GEEs) or hierarchical mixed-effects models and a multiblock partial least-squares regression analysis. These methods were applied to longitudinal data from two previous studies, i.e. a panel study and an intervention study involving 36 multiplier pig farms and 51 veal calf farms in the Netherlands, respectively. The multiblock analysis allowed us to quantify the importance of each factor and their respective block (i.e. farm management domain). For pigs, factors related to internal biosecurity had the highest impact on AMU, while for calves, these were mainly related to micro-climate. Structural characteristics, such as farm size and production type, followed in importance for both sectors. While both methods provided similar outcomes, the multiblock approach provided further insights by grouping and comparing factors believed to be inter-related.

A Systematic Review of Automatic Health Monitoring in Calves: Glimpsing the Future From Current Practice

Infectious diseases, particularly bovine respiratory disease (BRD) and neonatal calf diarrhea (NCD), are prevalent in calves. Efficient health-monitoring tools to identify such diseases on time are lacking. Common practice (i.e., health checks) often identifies sick calves at a late stage of disease or not at all. Sensor technology enables the automatic and continuous monitoring of calf physiology or behavior, potentially offering timely and precise detection of sick calves. A systematic overview of automated disease detection in calves is still lacking. The objectives of this literature review were hence: to investigate previously applied sensor validation methods used in the context of calf health, to identify sensors used on calves, the parameters these sensors monitor, and the statistical tools applied to identify diseases, to explore potential research gaps and to point to future research opportunities. To achieve these objectives, systematic literature searches were conducted. We defined four stages in the development of health-monitoring systems: (1) sensor technique, (2) data interpretation, (3) information integration, and (4) decision support. Fifty-four articles were included (stage one: 26; stage two: 19; stage three: 9; and stage four: 0). Common parameters that assess the performance of these systems are sensitivity, specificity, accuracy, precision, and negative predictive value. Gold standards that typically assess these parameters include manual measurement and manual health-assessment protocols. At stage one, automatic feeding stations, accelerometers, infrared thermography cameras, microphones, and 3-D cameras are accurate in screening behavior and physiology in calves. At stage two, changes in feeding behaviors, lying, activity, or body temperature corresponded to changes in health status, and point to health issues earlier than manual health checks. At stage three, accelerometers, thermometers, and automatic feeding stations have been integrated into one system that was shown to be able to successfully detect diseases in calves, including BRD and NCD. We discuss these findings, look into potentials at stage four, and touch upon the topic of resilience, whereby health-monitoring system might be used to detect low resilience (i.e., prone to disease but clinically healthy calves), promoting further improvements in calf health and welfare.

Large-size fattening calves' lots fed with automatic milk feeders may have an increased risk for Mycoplasma bovis infection spread and for antibiotic use

Bovine respiratory disease is the leading user of antibiotics (AB) in calf production. Mycoplasma (M.) bovis could lead to greater use of AB as it is a persistent and AB resistant causative agent for respiratory diseases. Two cross-sectional studies were set up to assess the effects of lot size and feeding system on M. bovis infection and the effects of M. bovis seroconversion, lot size and feeding system on AB use in calves' feedlots. Twenty-six lots in 22 fattening farms were monitored for 41-81 days, from all-in entry of calves until three consecutive weeks without using any collective antibiotics. M. bovis spread was estimated by measuring seroconversion at entry and at the end of study period in 10-15 calves randomly sampled in each lot. All AB treatments used in the meanwhile were recorded. The lots were selected according to feeding system, i.e. individual bucket (n = 7) vs. automated milk feeder (AMF, n = 19), and lot size (30-519 calves), less than 50 calves (n = 9) vs. more than 50 calves (n = 17). Statistical analysis was performed using multivariable generalised linear models with fattening farms as random effect. M. bovis spread increased with lot size (odds ratio (OR) 2.9[1.4; 5.8] per two-fold increase in lot size). This proportion of seroconverted calves was lower in bucket-fed lots compared to lots fed with the AMF using a shared nipple (OR = 0.03[0.003; 0.41]). The main risk factor for AB use was the lot size, with an increase of 1.5[0.94; 1.98] treatments per two-fold increase in lot size. For same size lots, the use of bucket can decrease AB consumption by up to 1.03[-2.18; 0.14] treatments per calf compared to AMF. Analysis of the association between seroconversion to M. bovis and AB use was inconclusive. We found that bucket feeding in small-size lots, i.e. up to a maximum of 50 calves in the same space, limits seroconversion to M. bovis and enables lower use of AB in veal calf production.

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

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

Prevalence of BRD-Related Viral Pathogens in the Upper Respiratory Tract of Swiss Veal Calves

The prevention of bovine respiratory disease is important, as it may lead to impaired welfare, economic losses, and considerable antimicrobial use, which can be associated with antimicrobial resistance. The aim of this study was to describe the prevalence of respiratory viruses and to identify risk factors for their occurrence. A convenience sample of 764 deep nasopharyngeal swab samples from veal calves was screened by PCR for bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (BPI3V), bovine coronavirus (BCoV), influenza D virus (IDV), and influenza C virus (ICV). The following prevalence rates were observed: BRSV, 2.1%; BPI3V, 3.3%; BCoV, 53.5%; IDV, 4.1%; ICV, 0%. Logistic mixed regression models were built for BCoV to explore associations with calf management and housing. Positive swab samples were more frequent in younger calves than older calves (>100 days; p < 0.001). The probability of detecting BCoV increased with increasing group size in young calves. Findings from this study suggested that young calves should be fattened in small groups to limit the risk of occurrence of BCoV, although an extended spectrum of risk factors for viral associated respiratory disorders such as nutritional aspects should be considered in future studies.

Occurrence of major and minor pathogens in calves diagnosed with bovine respiratory disease

Bovine respiratory disease (BRD) is caused by a mixture of viruses and opportunistic bacteria belonging to Pasteurellaceae and Mycoplasma bovis. However, these organisms are also commonly isolated from healthy calves. This study aimed to determine whether the organisms are present in higher numbers in calves sick with acute BRD than in clinically healthy calves, and further to genetically characterize bacteria of the family Pasteurellaceae to understand whether particular types are associated with disease. Forty-six clinically healthy and 46 calves with BRD were sampled by broncheoalveolar lavage (BAL) method in 11 herds geographically spread over Denmark to determine presence and quantity of microorganisms by culture and quantitative real time qPCR. Isolates of Pasteurellaceae were tested for antibiotic resistance and were whole genome sequenced to determine genotypes. Histophilus somni was in particular positively associated with BRD, suggesting particular importance of this organism as likely aetiology of BRD. In addition, quantification of bacteria revealed that higher counts of H. somni as well as of M. haemolytica was also a good indicator of the disease. Pasteurellaceae isolates were susceptible to the commonly used antibiotics in treatment of BRD, and genotypes were shared between isolates from clinically healthy and sick calves.

Estimating Clinically Relevant Cut-Off Values for a High-Throughput Quantitative Real-Time PCR Detecting Bacterial Respiratory Pathogens in Cattle

Bovine respiratory disease (BRD) results from interactions between pathogens, environmental stressors, and host factors. Obtaining a diagnosis of the causal pathogens is challenging but the use of high-throughput real-time PCR (rtPCR) may help target preventive and therapeutic interventions. The aim of this study was to improve the interpretation of rtPCR results by analysing their associations with clinical observations. The objective was to develop and illustrate a field-data driven statistical method to guide the selection of relevant quantification cycle cut-off values for pathogens associated with BRD for the high-throughput rtPCR system "Fluidigm BioMark HD" based on nasal swabs from calves. We used data from 36 herds enrolled in a Danish field study where 340 calves within pre-determined age-groups were subject to clinical examination and nasal swabs up to four times. The samples were analysed with the rtPCR system. Each of the 1,025 observation units were classified as sick with BRD or healthy, based on clinical scores. The optimal rtPCR results to predict BRD were investigated for Pasteurella multocida, Mycoplasma bovis, Histophilus somni, Mannheimia haemolytica, and Trueperella pyogenes by interpreting scatterplots and results of mixed effects logistic regression models. The clinically relevant rtPCR cut-off suggested for P. multocida and M. bovis was ≤ 21.3. For H. somni it was ≤ 17.4, while no cut-off could be determined for M. haemolytica and T. pyogenes. The demonstrated approach can provide objective support in the choice of clinically relevant cut-offs. However, for robust performance of the regression model sufficient amounts of suitable data are required.

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

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

Perspectives on the Management of Surplus Dairy Calves in the United States and Canada

The care of surplus dairy calves is a significant issue for the United States and Canadian dairy industries. Surplus dairy calves commonly experience poor welfare as evidenced by high levels of mortality and morbidity, and negative affective states resulting from limited opportunities to express natural behaviors. Many of these challenges are a result of a disaggregated production system, beginning with calf management at the dairy farm of origin and ending at a calf-raising facility, with some calves experiencing long-distance transportation and commingling at auction markets or assembly yards in the interim. Thus, the objectives of this narrative review are to highlight specific challenges associated with raising surplus dairy calves in the U.S. and Canada, how these challenges originate and could be addressed, and discuss future directions that may start with refinements of the current system, but ultimately require a system change. The first critical area to address is the management of surplus dairy calves on the dairy farm of origin. Good neonatal calf care reduces the risk of disease and mortality, however, many dairy farms in Canada and the U.S. do not provide sufficient colostrum or nutrition to surplus calves. Transportation and marketing are also major issues. Calves can be transported more than 24 consecutive hours, and most calves are sold through auction markets or assembly yards which increases disease exposure. Management of calves at calf-raisers is another area of concern. Calves are generally housed individually and fed at low planes of nutrition, resulting in poor affective states and high rates of morbidity and mortality. Strategies to manage high-risk calves identified at arrival could be implemented to reduce disease burden, however, increasing the plane of nutrition and improving housing systems will likely have a more significant impact on health and welfare. However, we argue the current system is not sustainable and new solutions for surplus calves should be considered. A coordinated and holistic approach including substantial change on source dairy farms and multiple areas within the system used to market and raise surplus dairy calves, can lead to more sustainable veal and beef production with improved calf outcomes.

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).

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.

Feeding behaviour and activity as early indicators of disease in pre-weaned dairy calves

Across the industry, there is large variation in health status of dairy calves and as a result, disease incidence and antibiotic use is high. This has significant implications for animal welfare, productivity and profitability of dairy and dairy-beef production systems. Technology-based early detection systems could alleviate these issues; however, methods of early detection of disease in dairy calves have not been widely explored. This study aimed to determine whether changes in activity and feeding behaviour can be used as early warning indicators of respiratory disease in calves. In total, 100 pre-weaned male Holstein calves (age: ~8-42 days) were used. Calves were group-housed and provided with starter diet, straw bedding and ad libitum water. Calves were fed milk replacer ad libitum through an automatic calf feeder, and each calf was fitted with a leg-mounted activity monitor. Daily activity and feeding behaviour variables were calculated for each calf. Each calf was assessed daily using a modified version of the Wisconsin Scoring System to assess respiratory disease status. Calves were classed as 'Diseased', 'Intermediate' or 'Healthy' based on their cumulative health score. The peak day of the most extreme illness event was identified for each calf. Data from Diseased and Healthy calves were paired for analysis based on age and BW. Data were compared for the day of peak illness, and for the 3 days previous and post. Compared to healthy calves, diseased calves lay for longer and tended to have longer lying bouts (daily lying: 17.6 ± 0.3 vs 16.7 ± 0.2 h, P < 0.01; bout length: 74.8 ± 10.6 vs 56.0 ± 3.7 min, P = 0.09 for diseased and healthy calves, respectively). Diseased calves fed for a shorter time and had fewer feeder visits (with intake) each day compared to healthy calves (feeding time (min): 19.3 ± 1.4 vs 22.8 ± 1.5; P < 0.05; visits: 2.1 ± 0.2 vs 3.2 ± 0.4; P < 0.05). Importantly, differences between diseased and healthy calves were evident in both activity and feeding behaviour on the days prior to the peak day of disease. Lying bout length was greater in diseased calves for the 2 days prior to the peak day (P < 0.05), lying time was longer on day -1 (P < 0.05) and feeder visits with milk intake were less frequent on day -3 (P < 0.05). Thus, measurement of feeding and activity using precision technology within early detection systems could facilitate early intervention and optimized treatment.

Transport of Young Veal Calves: Effects of Pre-transport Diet, Transport Duration and Type of Vehicle on Health, Behavior, Use of Medicines, and Slaughter Characteristics

The aim of this study was to investigate effects of different early life transport-related factors on health, behavior, use of medicines and slaughter characteristics of veal calves. An experiment was conducted with a 2 × 2 × 2 factorial arrangement with 3 factors: (1) provision of rearing milk or electrolytes before transport, (2) transport duration (6 or 18 h), and (3) type of vehicle (open truck or conditioned truck). The study included male Holstein-Friesian and cross-bred calves (N = 368; 18 ± 4 days; 45.3 ± 3.3 kg). Data on health status of calves were collected at the collection center and at the veal farm until week 27 post-transport. Behavior of calves was recorded during transport and at the veal farm until week 13 post-transport. Use of herd and individual medical treatments was recorded at the veal farm. The prevalence of loose or liquid manure at the veal farm from day 1 until week 3 post-transport was lower in electrolyte-fed calves transported in the conditioned truck compared to electrolytes-fed calves transported in the open truck or milk-fed calves transported in both the conditioned and open truck (Δ = 11% on average; P = 0.02). In comparison with the open truck, calves transported in the conditioned truck had lower prevalence of navel inflammation in the first 3 weeks post-transport (Δ = 3 %; P = 0.05). More milk-fed calves received individual antibiotic treatments compared to electrolyte-fed calves at the veal farm (P = 0.05). In conclusion, the transport-related factors examined in the present study affected health and behavior of calves in the short-term, but there was no evidence for long-term effects. It remains unknown why no long-term effects were found in this study. Perhaps this absence of transport-related effects was due to multiple use of medical treatments in the first weeks at the veal farm. Alternatively, it might be that the collective effects of the transition from the dairy farm to the veal farm, and of the husbandry conditions during the subsequent rearing period, on the adaptive capacity of calves were so large that effects of individual transport-related factors were overruled.

Identification of biomarkers measured upon arrival associated with morbidity, mortality, and average daily gain in grain-fed veal calves

There is a strong need for management strategies that help reduce the incidence of disease and subsequent antimicrobial use in the veal industry. Biomarkers could serve as useful tools that allow producers to take preventative measures before clinical problems occur. The objective of this prospective cohort study was to identify biomarkers measured upon arrival associated with morbidity, mortality, and average daily gain (ADG) in grain-fed veal calves. Upon arrival at a grain-fed veal facility in Ontario, Canada, calves were weighed and health-scored using a standardized health-scoring system. Several metabolites were measured including creatine kinase (CK), cholesterol, haptoglobin, manganese, serum total protein, iron, cobalt, zinc, selenium, molybdenum, and IgG. Farm personnel treated calves according to their farm protocol and weighed them at 78 d after arrival. Performance, treatment, and mortality records from the facility were used for analysis. Multivariable Cox proportional hazard models were created to evaluate metabolic biomarkers associated with morbidity and mortality. A mixed linear regression model was created to determine biomarkers associated with ADG. A total of 992 male dairy calves were evaluated at arrival from January to December 2017. Of the calves evaluated, 74 calves (7.5%) died and 877 (88.4%) were treated for illness over the 11-wk period under observation. Higher levels of haptoglobin and molybdenum were associated with a greater hazard of morbidity, whereas higher weight upon arrival and higher levels of both CK and IgG were associated with a reduced hazard of morbidity. For mortality, higher weight upon arrival and higher levels of cholesterol and IgG were associated with a lower hazard of mortality occurring over the 78-d period of observation. Higher weight, cholesterol, copper, CK, iron, and IgG were associated with increased ADG, whereas increased zinc and haptoglobin were negatively associated with ADG. These results demonstrate that certain biomarkers could be used to identify high-risk calves when measured upon arrival at a veal facility. Future research should focus on determining the utility of these biomarkers to selectively target intervention strategies to improve ADG and reduce morbidity and mortality.

Welfare Assessment in Calves Fattened According to the "Outdoor Veal Calf" Concept and in Conventional Veal Fattening Operations in Switzerland

Simple Summary

Antimicrobial use in humans and animals leads to the selection of resistant bacteria, a serious threat to human and animal health, as such bacteria can lead to treatment failure and death. With the “outdoor veal calf” concept, a novel calf fattening system was developed that allows for reducing antimicrobial use by 80% through improvements in management and housing, such as health check before purchase, short transport, vaccination, quarantine in individual hutches, and fattening in small groups in a roofed, straw-bedded paddock with a group hutch for shelter. In that system, veal calves spend their entire lives outdoors in the fresh air. In our study, we wanted to make sure that the observed reduction in antimicrobial treatments was not achieved at the cost of animal welfare, i.e., that sick animals were not left without treatment in order to obtain better figures for treatment reduction. Our results show that calves in the “outdoor veal calf” system had fewer signs of respiratory and digestive diseases than control calves and that their lungs had fewer lesions of pneumonia than controls after slaughter. Thus, not only was antimicrobial use drastically reduced, but calf health was really improved in the new “outdoor veal calf” system.

Abstract

The “outdoor veal calf” system was developed to encounter the demand for a veal fattening system that allows for reducing antimicrobial use without impairing animal welfare. Management improvements including direct purchase, short transportation, vaccination, three-week quarantine in individual hutches, and open-air housing in small groups in a roofed, straw-bedded paddock with a group hutch were implemented in a prospective intervention study (1905 calves, 19 intervention and 19 control farms, over one year): antimicrobial use was five times lower in "outdoor veal" farms compared to control farms (p < 0.001), but it was crucial to ensure that antimicrobial treatment reduction was not associated with decreased animal welfare, i.e., that sick animals were not left untreated. Welfare was assessed monthly on the farms, and organs of 339 calves were examined after slaughter. Cough and nasal discharge were observed significantly (p ≤ 0.05) less often in intervention than in control farms, mortality (3.1% vs. 6.3%, p = 0.020) and lung lesion prevalence (26% vs. 46%, p < 0.001) were lower; no group difference was seen in abomasal lesion prevalence (65% vs. 72%). Thus, besides reduced antimicrobial use, calf health and welfare were improved in "outdoor veal calf" farms in comparison to traditional operations.

Production Significance of Bovine Respiratory Disease Lesions in Slaughtered Beef Cattle

Bovine respiratory disease (BRD) is still a serious concern in feedlots, where it exerts a negative effect on farm productivity. There is a shortage of studies focused on the evaluation of BRD-associated lesions at the slaughterhouse in clinically healthy animals. The objective of this work was to investigate the prevalence and type of subclinical pneumonic lesions in slaughtered beef cattle, according to the age range and management system, and its impact on carcass weight. A total of 1101 beef cattle intended for human consumption were examined at slaughter. Information on age, sex, management system and carcass weight was recorded. The presence and type of pneumonia were evaluated according to gross and microscopic findings and etiological agents by PCR. Lung pneumonic lesions appeared in 17.9% of animals and were predominant among veal calves. According to the type, chronic catarrhal pneumonia prevailed in the majority of animals, and mixed and extensively reared cattle were more likely to suffer acute fibrinous pneumonia. The presence of pneumonic lesions was associated with a significant decrease in carcass weight that had more of an impact in veal male calves coming from intensive systems. Bacterial infections were the predominant infectious agent and the only cause of acute fibrinous pneumonia, while viruses were infrequent and only found in lesions with chronic catarrhal pneumonia. This study shows the importance of BRD in beef feedlots upon production values and points out the feasibility of slaughterhouse assessment of pneumonia as a method for the evaluation of BRD significance.

The Effect of Co-Administration of Inactivated Vaccines Against Bovine Respiratory Disease and Neonatal Calf Diarrhoea

A pilot study was performed to evaluate the safety and serological responses after co-administration of two multivalent inactivated vaccines to pregnant cattle. One vaccine was directed against bovine respiratory disease (BRD) and contained antigens of bovine respiratory syncytial virus (BRSV), parainfluenza 3 virus (PI3) and Mannheimia haemolytica (Mh). The second vaccine targeted neonatal calf diarrhoea (NCD) and was composed of inactivated antigens of bovine rotavirus (BRV), bovine coronavirus (BCV) and E. coli. The use of these combinations have been used more and more by veterinary practitioners as there exist some clear evidence that both vaccines improves the passive protection via the colostrum for the relevant pathogens. However, up until now, no safety or efficacy data has been available concerning such co-administrations. The safety of both vaccines and the serological responses to the BRD vaccine has been evaluated when used at the same time, but without mixing and compared to the responses to the administration of each vaccine independently. There was no evidence of any negative effect on calving or calf health in any of the vaccinated animals. The antibody levels against BRSV and Mh in the sera of the calves from cows vaccinated with both vaccines were not significantly different from the levels in the sera of calves vaccinated with the BRD vaccine alone. The results from this pilot study demonstrated that the co-administration of the two multivalent inactivated vaccines had no detrimental effect on the safety or serological responses to the BRD vaccine compared to the independent use of the vaccines.

How Does Housing Influence Bovine Respiratory Disease in Dairy and Veal Calves?

Bovine respiratory disease (BRD) is a leading cause of morbidity and mortality in young cattle. Housing factors that lead to poor ventilation and stagnant air are often considered the primary reasons for high levels of endemic disease. This article reviews the literature from the past 40 years in order to determine which housing factors have been associated with respiratory disease. Penning strategy and its affect on calf respiratory health were most commonly studied. The wide variation in disease definitions and quality of reporting make drawing conclusions from the available literature extraordinarily difficult.

Dairy Calf Welfare and Factors Associated with Diarrhea and Respiratory Disease Among Chilean Dairy Farms

Simple Summary

Since 2013, a Chilean law regulates the welfare of farm animals. Despite advances in scientific knowledge and legislation, many farms use management practices that can be detrimental to animals. The objectives of this study were to describe common management practices that may affect the welfare status of unweaned dairy calves and identify factors associated with diarrhea and respiratory disease. We visited 29 dairy farms and collected information on management practices, environment, and animal health. Management practices identified as risk factors for poor calf welfare were: reliance on the mother to provide colostrum, use of restrictive milk feeding (<4 L/day), disbudding performed with no pain control, and lack of appropriate euthanasia protocols. Factors associated with diarrhea were: frequency of bed cleaning, calf cleanliness score, type of milk, and herd size. Factors associated with respiratory disease were: calf cleanliness score, pen space allowance, and colostrum quality evaluation. Showing critical points that impact the health and welfare of dairy calves facilitates the implementation of improvement strategies.

Abstract

This study aimed to describe management practices that may compromise the welfare of unweaned dairy calves on 29 dairy farms in Chile, and identify factors associated with diarrhea and respiratory disease (n = 700 calves). Evaluations were divided into protocol-, facility-, and animal-based measurements. Calf diarrhea and respiratory disease data were analyzed using logistic regression models. Management practices identified as risk factors for poor calf welfare were: relying on the mother to provide colostrum (48.0% of the farms); using restrictive milk feeding (65.5%), and unpasteurized waste milk (51.7%); giving water after 30 days of age (17.2%); disbudding without analgesia (89.6%) or anesthesia (79.3%); lacking euthanasia protocols (61.5%). Factors significantly (p < 0.05) associated with increased odds of diarrhea were: cleaning the calves’ bed once a week and 2–3 times a week compared with every day, using milk replacer and untreated waste milk compared with treated waste milk (pasteurized or acidified), animals scored dirty in the calf cleanliness score compared with clean animals, and greater herd size. Factors significantly associated with increased odds of respiratory disease were: less pen space allowance (<1.8 m²), farms that did not check colostrum quality, and animals that scored dirty and moderately dirty compared with clean calves. These results suggest the need to improve specific management practices associated with reduced welfare and health in dairy calves in Chile.

Stakeholders' perceptions of the challenges to improving calf health and reducing antimicrobial use in Swiss veal production

Large quantities of antimicrobials are used in Swiss veal production. To develop strategies to reduce antimicrobial use, it is important to understand how stakeholders along the veal production chain perceive the current situation and to find the key issues that challenge them about calf health management and antimicrobial use. However, there has been insufficient research into the individual contexts of the supply chain actors, and the central themes that they perceive to enable or limit their actions remain largely unknown. The aim of this study is to investigate the perceptions of the current situation of the Swiss veal production system, in terms of calf health management and antimicrobial use held by industry stakeholders, i.e. dairy farmers, veal producers, traders, slaughterhouse managers, advisors and veterinarians. Qualitative interviews were conducted with 27 respondents and analyzed using content analysis. The results show that stakeholders are aware of the current need to minimize resistance development and the related risks for public health by reducing antimicrobial use. The main reason for high antimicrobial use was nominated as the practice of purchasing calves from many different dairy farms and bringing them together in large groups at a young age, which exposes them to a variety of pathogens that their still developing immune systems are not able to cope with. To prevent and combat infectious diseases which are a frequent consequence of this practice, antimicrobial group treatments are commonly administered, which significantly raises the total amount of antimicrobials used. Group level treatments with antimicrobials were associated directly with the large-scale veal farming system, which uses excess calves from specialized dairy farms, and which the respondents perceive to cause financial pressure and mutual dependencies among participants. In addition, disunity between actors was perceived as a further challenge to find strategies for the reduction of antimicrobial use. The respondents suggested downscaling the production system so that calves can be treated individually but conceded that the current system may be very difficult to change, so also suggested various improvement measures within the existing system. The results of this study provide a basis for further research to investigate possible interventions that could considerably reduce antimicrobial use in veal production.

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.

Health and growth of veal calves provided a fatty acid supplement and a dry teat

Veal calves are at a high risk of disease early in life, which can lead to poor growth. Research is needed to determine interventions that can reduce disease and promote the growth of veal calves. The aim of this study was to determine the effects of fatty acid supplementation and the provision of a dry teat on the incidence of bovine respiratory disease (BRD), navel inflammation, and diarrhea, as well as calf growth. Upon arrival to a commercial veal facility (d 0), 240 Holstein bull calves from 2 cohorts were randomly assigned to 4 treatments using a 2 × 2 factorial arrangement (n = 60/treatment): (1) milk replacer (MR) without fatty acid supplementation and without access to a dry teat (control), (2) MR with fatty acid supplementation (NeoTec5g, Provimi, Brookville, OH) and without access to a dry teat (FAS), (3) MR without fatty acid supplementation and with access to a dry teat (TT), or (4) MR with fatty acid supplementation and with access to a dry teat (FAS+TT). Calves were housed in individual pens from 0 to 9 wk and then paired by treatment at wk 9. Milk replacer was fed twice daily using a step-up program. Fatty acid supplement was added to milk replacer at a feeding rate of 0.5 g/kg of body weight per head per day for the FAS and FAS+TT groups. Health exams were conducted twice weekly for 6 wk to diagnose BRD, navel inflammation, and diarrhea. Body weight, body condition score (BCS), and structural measurements were recorded at wk 0, 5, and 10. Average daily gain (ADG) was calculated for wk 1 to 5, wk 5 to 10, and wk 1 to 10. Health data were analyzed using logistic regression and are reported as relative risk. Body weight, BCS, and structural measurements were analyzed using repeated-measures ANOVA, and ADG was analyzed using a generalized linear model. There was no effect of FAS, TT, or their interaction on body weight or BCS. There was no effect of FAS on ADG wk 1 to 5, wk 5 to 10, or wk 1 to 10. There was a tendency for TT to decrease ADG from wk 1 to 5 but not from wk 5 to 10 or wk 1 to 10. There was a tendency for the interaction of FAS and TT to decrease ADG for wk 1 to 5 but not for wk 5 to 10 and wk 1 to 10. There was no effect of FAS, TT, or their interaction on the risk of BRD, diarrhea, or navel inflammation. We saw no effect of our interventions on calf health or growth. More research is needed to determine whether other factors, such as failure of passive transfer, poor ventilation, barren housing, and low milk allowance in the first few weeks after arrival, may have affected the efficacy of our interventions.

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.

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.

Effect of health status upon arrival at a single milk-fed veal facility on breakeven purchase price of calves

Male calves are purchased from the dairy industry in North America to produce red meat. The price paid for male calves varies widely, and it is unclear which variables influence the price paid for each calf. The objective of this study was to assess how the health traits of calves at the time of arrival and demographic variables affect the breakeven purchase price of a male calf entering the veal industry. A financial model was constructed using the prevalence of health abnormalities, weight at arrival, source of the calf, number of days in the barn, base carcass price, days to mortality, feed costs, season at arrival, interest rate, housing location, carcass dressing percentage, and costs associated with housing, labor, utilities, trucking, and health to calculate the breakeven purchase price and an estimate of profit. Sensitivity analysis was conducted using health variables measured at arrival and demographic variables, including season at arrival and housing location, to identify the factors with the largest impact on the predicted average daily gain, early and late mortality risk, breakeven purchase price, and profit. At the baseline inputs, the average calculated profit was -$5.36 per calf and it was most sensitive to the location of housing where calves were fed and the body weight of the arriving calf. The mortality risk in the first 21 d after arrival (early) was calculated to be 2.2%, whereas the risk of mortality after 21 d (late) was 3.7%. The risks of early and late mortality were most sensitive to the level of dehydration measured at arrival and the season at arrival for the purchased calves, respectively. The calculated average daily gain was 1.12 kg/d and it was most sensitive to housing location. The breakeven purchase price was calculated to be $242.49 per calf, which was most sensitive to the housing location where the calves were fed. The results of this analysis demonstrate that veal producers need to consider many variables before purchasing calves. In addition to overall market conditions, veal producers should factor health characteristics and the expected performance of the calves they purchase into what they are willing to pay for them.

Health parameters and their association with price in young calves sold at auction for veal operations in Québec, Canada

The veal calf industry in Québec depends on young calves' availability at auction. Most of these calves come from dairy farms. The aim of this cross-sectional study was to determine the effect of clinical anomalies and other calf characteristics on their sale price. A total of 3,820 calves from 5 different auctions were included in this observational study. The calves were examined by a veterinarian on arrival at the auction and screened for umbilical anomalies, the presence of nasal or eye discharge, joint abnormality, diarrhea, appearance of neonatal characteristics (compatible with age less than 1 wk), and general health status mainly based on the presence of depression and dehydration. The final multivariable model included 5 different variables (calf weight, sex, breed, abnormal joints, and general health status) and the interaction between sex and general health status. The presence of abnormal joints and unhealthy characteristics was negatively associated with standardized price. Female calves and mixed breed beef calves were positively associated with standardized price. Finally, the calves' weight was associated with standardized price in a quadratic fashion. Ongoing or previous diarrhea had no effects on standardized price. This study will be helpful for both dairy and veal producers for improving the quality of calves sold to the Québec auction market.

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.

Effects of management practices, animal transport and barn climate on animal health and antimicrobial use in Swiss veal calf operations

To assess the effects of transport, management factors and barn climate on calf health, 43 Swiss veal farms (11 large farms fattening ≥100 calves and 32 small farms fattening >20 but <100 calves per year) were monitored in a prospective cohort study over a period of one year. Detailed questionnaires on farm structure, management, housing system and animal health were filled out with the farmers during bimonthly visits, and barn temperature, humidity, ammonia and CO₂ concentrations were measured. Temperature and humidity were also measured continuously over 72 h once each in winter and summer. In addition, calf purchase and transport from birth farm to fattening unit were documented by the farmers, and the study team accompanied one transport per farm whenever possible. Antimicrobial treatment incidence was calculated from the used daily dose (TI_UDD). Risk factors for mortality, average daily weight gain (ADG) and antimicrobial use, as well as factors related to transport and barn climate measures were evaluated with mixed regression models. The overall mortality rate was 5.1% (6.2% in large herds and 3.1% in small ones). Identified risk factors for mortality >3% included a lower number of calves fattened per year and a good hygiene of the feeder. This surprising result was likely due to the fact that the threshold of 3% mortality was rather exceeded in smaller farms. Furthemore, higher temperature variation (range between maximal and minimal temperature over 3 measurement days) in the calf pen was associated with mortality >3% in the univariable analysis. The overall mean ADG was 1.40 ± 0.16 kg. Calf purchase was significantly associated with decreased ADG. The median overall TI_UDD was eight daily doses per calf and year (2.1 in small farms and 26 in large farms, respectively); the main indication for treatment was respiratory disease (81.1%). Risk factors for increased TI were no quarantine upon arrival, access to an outside pen, higher numbers of calves per drinking nipple, mechanical ventilation, vaccination against bovine respiratory disease, and a maximum ammonia value >10 ppm in the calf pen. In addition, a higher number of birth farms and calf purchase from markets were associated with increased TI in the univariable analysis. The identified risk factors associated with increased TI and mortality and with decreased ADG should be addressed in priority in veal calf operations to improve calf health and reduce antimicrobial use.

Effect of age on the pharmacokinetics and distribution of tulathromycin in interstitial and pulmonary epithelial lining fluid in healthy calves

OBJECTIVE To compare the plasma pharmacokinetics of tulathromycin between 3-week-old (preweaned) and 6-month-old (weaned) calves and to characterize the distribution of tulathromcyin into pulmonary epithelial lining fluid (PELF) and interstitial fluid (ISF) of preweaned and weaned calves following SC administration of a single dose (2.5 mg/kg). ANIMALS 8 healthy 3-week-old and 8 healthy 6-month-old Holstein steers. PROCEDURES A jugular catheter and SC ultrafiltration probe were aseptically placed in the neck of each calf before tulathromycin administration. Blood, ISF, and bronchoalveolar lavage fluid samples were collected at predetermined times before and after tulathromycin administration for quantification of drug concentration. A urea dilution method was used to estimate tulathromycin concentration in PELF from that in bronchoalveolar lavage fluid. Tulathromycin-plasma protein binding was determined by in vitro methods. Plasma pharmacokinetics were determined by a 2-compartment model. Pharmacokinetic parameters and drug concentrations were compared between preweaned and weaned calves. RESULTS Clearance and volume of distribution per fraction of tulathromycin absorbed were significantly greater for weaned calves than preweaned calves. Tulathromycin-plasma protein binding was significantly greater for weaned calves than preweaned calves. Maximum PELF tulathromycin concentration was significantly greater than the maximum plasma and maximum ISF tulathromycin concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that age affected multiple pharmacokinetic parameters of tulathromycin, likely owing to physiologic changes as calves mature from preruminants to ruminants. Knowledge of those changes may be useful in the development of studies to evaluate potential dose adjustments during treatment of calves with respiratory tract disease.

Effect of health status evaluated at arrival on growth in milk-fed veal calves: A prospective single cohort study

The objective of this prospective single cohort study was to determine the effect of health status at arrival on growth in milk-fed veal calves. Upon arrival at the veal facility, calves were evaluated using a standardized health scoring system and weighed, and the supplier of the calf was recorded. The calves were followed until slaughter, when the hot carcass weight (HCW) was reported. To calculate average daily gain (ADG), the HCW was transformed into an estimated live weight, weight at arrival was subtracted, and this value was divided by the number of days on feed. A mixed linear regression model was created to evaluate the association of health status on arrival with the ADG throughout the production period. A total of 4,825 calves were evaluated at arrival; however, due to inconsistent HCW data from one slaughter plant, and 357 calves dying during the production period, 2,283 calves were used for analysis. In the final model, 7 variables were significantly associated with ADG. Housing location within the farm, method of calf procurement (drover or auction-derived calves versus direct delivery from local farms) and having a higher body weight at arrival were associated with a higher ADG. The season of arrival (summer or fall compared with winter) and being dehydrated at arrival were associated with a lower ADG. Days on feed was also significant in the multivariable model and had a quadratic relationship with ADG. The associations identified suggest that there may be value in scoring dehydration and body weight at arrival to a veal facility.