Machine Learning Methods and Visual Observations to Categorize Behavior of Grazing Cattle Using Accelerometer Signals.

Accelerometers worn by animals produce distinct behavioral signatures, which can be classified accurately using machine learning methods such as random forest decision trees. The objective of this study was to identify accelerometer signal separation among parsimonious behaviors. We achieved this objective by (1) describing functional differences in accelerometer signals among discrete behaviors, (2) identifying the optimal window size for signal pre-processing, and (3) demonstrating the number of observations required to achieve the desired level of model accuracy,. Crossbred steers (Bos taurus indicus; n = 10) were fitted with GPS collars containing a video camera and tri-axial accelerometers (read-rate = 40 Hz). Distinct behaviors from accelerometer signals, particularly for grazing, were apparent because of the head-down posture. Increasing the smoothing window size to 10 s improved classification accuracy (p < 0.05), but reducing the number of observations below 50% resulted in a decrease in accuracy for all behaviors (p < 0.05). In-pasture observation increased accuracy and precision (0.05 and 0.08 percent, respectively) compared with animal-borne collar video observations.

Tulathromycin metaphylaxis increases nasopharyngeal isolation of multidrug resistant Mannheimia haemolytica in stocker heifers.

Bovine respiratory disease (BRD) is a leading cause of disease in feedlot and stocker calves with Mannheimia haemolytica (MH) as one of the most common etiologies. One of the most effective means of controlling BRD is through metaphylaxis, which involves administering antimicrobials to all animals at high risk of developing BRD. However, increasing prevalence of multidrug resistant (MDR) MH may reduce efficacy of metaphylaxis due to decreased susceptibility to drugs used for metaphylaxis. Primarily, this study aimed to determine the effect of tulathromycin metaphylaxis and subsequent BRD treatment on antimicrobial resistance (AMR) in MH isolated from stocker calves. Secondary objectives included evaluating the effect of metaphylaxis and treatment for BRD on animal health and comparing the genetic relationship of MH isolated. Crossbred beef heifers (n = 331, mean weight = 232, SD = 17.8 kg) at high risk for BRD were randomly assigned to receive tulathromycin metaphylaxis (META, n = 167) or not (NO META, n = 164). Nasopharyngeal swabs were collected for MH isolation, antimicrobial susceptibility testing and whole genome sequencing at arrival and 3 (WK3) and 10 (WK10) weeks later. Mixed-effects logistic regression was used to identify risk factors for isolation of MH and MDR MH (resistant to ≥3 antimicrobial drug classes) at 3 and 10 weeks, BRD morbidity, and crude mortality. Animals in the META group had higher odds of isolation of MDR MH at 3 weeks [OR (95% CI) = 13.08 (5-30.9), p < 0.0001] and 10 weeks [OR (95% CI) = 5.92 (1.34-26.14), p = 0.019] after arrival. There was no difference in risk of isolation of any MH (resistant or susceptible) between META and NO META groups at all timepoints. Animals in the NO META group had 3 times higher odds of being treated for BRD [WK3: OR (95% CI) = 3.07 (1.70-5.52), p = 0.0002; WK10: OR (95% CI) = 2.76 (1.59-4.80), p = 0.0002]. Antimicrobial resistance genes found within isolates were associated with integrative conjugative element (ICE) genes. Tulathromycin metaphylaxis increased risk of isolation of MDR MH and in this population, the increase in MDR MH appeared to be associated with ICE containing antimicrobial resistance genes for multiple antimicrobial classes. This may have important implications for future efficacy of antimicrobials for control and treatment of BRD.

Influence of the At-Arrival Host Transcriptome on Bovine Respiratory Disease Incidence during Backgrounding.

Bovine respiratory disease (BRD) remains the leading disease within the U.S. beef cattle industry. Marketing decisions made prior to backgrounding may shift BRD incidence into a different phase of production, and the importance of host gene expression on BRD incidence as it relates to marketing strategy is poorly understood. Our objective was to compare the influence of marketing on host transcriptomes measured on arrival at a backgrounding facility on the subsequent probability of being treated for BRD during a 45-day backgrounding phase. This study, through RNA-Seq analysis of blood samples collected on arrival, evaluated gene expression differences between cattle which experienced a commercial auction setting (AUCTION) versus cattle directly shipped to backgrounding from the cow-calf phase (DIRECT); further analyses were conducted to determine differentially expressed genes (DEGs) between cattle which remained clinically healthy during backgrounding (HEALTHY) versus those that required treatment for clinical BRD within 45 days of arrival (BRD). A profound difference in DEGs (n = 2961) was identified between AUCTION cattle compared to DIRECT cattle, regardless of BRD development; these DEGs encoded for proteins involved in antiviral defense (increased in AUCTION), cell growth regulation (decreased in AUCTION), and inflammatory mediation (decreased in AUCTION). Nine and four DEGs were identified between BRD and HEALTHY cohorts in the AUCTION and DIRECT groups, respectively; DEGs between disease cohorts in the AUCTION group encoded for proteins involved in collagen synthesis and platelet aggregation (increased in HEALTHY). Our work demonstrates the clear influence marketing has on host expression and identified genes and mechanisms which may predict BRD risk.

Hematological and gene co-expression network analyses of high-risk beef cattle defines immunological mechanisms and biological complexes involved in bovine respiratory disease and weight gain.

Bovine respiratory disease (BRD), the leading disease complex in beef cattle production systems, remains highly elusive regarding diagnostics and disease prediction. Previous research has employed cellular and molecular techniques to describe hematological and gene expression variation that coincides with BRD development. Here, we utilized weighted gene co-expression network analysis (WGCNA) to leverage total gene expression patterns from cattle at arrival and generate hematological and clinical trait associations to describe mechanisms that may predict BRD development. Gene expression counts of previously published RNA-Seq data from 23 cattle (2017; n = 11 Healthy, n = 12 BRD) were used to construct gene co-expression modules and correlation patterns with complete blood count (CBC) and clinical datasets. Modules were further evaluated for cross-populational preservation of expression with RNA-Seq data from 24 cattle in an independent population (2019; n = 12 Healthy, n = 12 BRD). Genes within well-preserved modules were subject to functional enrichment analysis for significant Gene Ontology terms and pathways. Genes which possessed high module membership and association with BRD development, regardless of module preservation ("hub genes"), were utilized for protein-protein physical interaction network and clustering analyses. Five well-preserved modules of co-expressed genes were identified. One module ("steelblue"), involved in alpha-beta T-cell complexes and Th2-type immunity, possessed significant correlation with increased erythrocytes, platelets, and BRD development. One module ("purple"), involved in mitochondrial metabolism and rRNA maturation, possessed significant correlation with increased eosinophils, fecal egg count per gram, and weight gain over time. Fifty-two interacting hub genes, stratified into 11 clusters, may possess transient function involved in BRD development not previously described in literature. This study identifies co-expressed genes and coordinated mechanisms associated with BRD, which necessitates further investigation in BRD-prediction research.

Impact of preweaning vaccination on host gene expression and antibody titers in healthy beef calves.

The impact of preweaning vaccination for bovine respiratory viruses on cattle health and subsequent bovine respiratory disease morbidity has been widely studied yet questions remain regarding the impact of these vaccines on host response and gene expression. Six randomly selected calves were vaccinated twice preweaning (T1 and T3) with a modified live vaccine for respiratory pathogens and 6 randomly selected calves were left unvaccinated. Whole blood samples were taken at first vaccination (T1), seven days later (T2), at revaccination and castration (T3), and at weaning (T4), and utilized for RNA isolation and sequencing. Serum from T3 and T4 was analyzed for antibodies to BRSV, BVDV1a, and BHV1. Sequenced RNA for all 48 samples was bioinformatically processed with a HISAT2/StringTie pipeline, utilizing reference guided assembly with the ARS-UCD1.2 bovine genome. Differentially expressed genes were identified through analyzing the impact of time across all calves, influence of vaccination across treatment groups at each timepoint, and the interaction of time and vaccination. Calves, regardless of vaccine administration, demonstrated an increase in gene expression over time related to specialized proresolving mediator production, lipid metabolism, and stimulation of immunoregulatory T-cells. Vaccination was associated with gene expression related to natural killer cell activity and helper T-cell differentiation, enriching for an upregulation in Th17-related gene expression, and downregulated genes involved in complement system activity and coagulation mechanisms. Type-1 interferon production was unaffected by the influence of vaccination nor time. To our knowledge, this is the first study to evaluate mechanisms of vaccination and development in healthy calves through RNA sequencing analysis.

Assessment of Diversity of Antimicrobial Resistance Phenotypes and Genotypes of Mannheimia haemolytica Isolates From Bovine Nasopharyngeal Swabs.

The threat of bovine respiratory disease (BRD) for cattle operations is exacerbated by increasing prevalence of antimicrobial resistance (AMR) in Mannheimia haemolytica, a leading cause of BRD. Characterization of AMR in M. haemolytica by culture and susceptibility testing is complicated by uncertainty regarding the number of colonies that must be selected to accurately characterize AMR phenotypes (antibiograms) and genotypes in a culture. The study objective was to assess phenotypic and genotypic diversity of M. haemolytica isolates on nasopharyngeal swabs (NPS) from 28 cattle at risk for BRD or with BRD. NPS were swabbed onto five consecutive blood agar plates; after incubation up to 20 M. haemolytica colonies were selected per plate (up to 100 colonies per NPS). Phenotype was determined by measuring minimum inhibitory concentrations (MIC) for 11 antimicrobials and classifying isolates as resistant or not. Genotype was indirectly determined by matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS). NPS from 11 of 28 cattle yielded at least one M. haemolytica isolate; median (range) of isolates per NPS was 48 (1-94). NPS from seven cattle yielded one phenotype, 3 NPS yielded two, and 1 NPS yielded three; however, within a sample all phenotypic differences were due to only one MIC dilution. On each NPS all M. haemolytica isolated were the same genotype; genotype 1 was isolated from three NPS and genotype two was isolated from eight. Diversity of M. haemolytica on bovine NPS was limited, suggesting that selection of few colonies might adequately identify relevant phenotypes and genotypes.

Use of nCounter mRNA profiling to identify at-arrival gene expression patterns for predicting bovine respiratory disease in beef cattle.

BACKGROUND: Transcriptomics has identified at-arrival differentially expressed genes associated with bovine respiratory disease (BRD) development; however, their use as prediction molecules necessitates further evaluation. Therefore, we aimed to selectively analyze and corroborate at-arrival mRNA expression from multiple independent populations of beef cattle. In a nested case-control study, we evaluated the expression of 56 mRNA molecules from at-arrival blood samples of 234 cattle across seven populations via NanoString nCounter gene expression profiling. Analysis of mRNA was performed with nSolver Advanced Analysis software (p < 0.05), comparing cattle groups based on the diagnosis of clinical BRD within 28 days of facility arrival (n = 115 Healthy; n = 119 BRD); BRD was further stratified for severity based on frequency of treatment and/or mortality (Treated_1, n = 89; Treated_2+, n = 30). Gene expression homogeneity of variance, receiver operator characteristic (ROC) curve, and decision tree analyses were performed between severity cohorts. RESULTS: Increased expression of mRNAs involved in specialized pro-resolving mediator synthesis (ALOX15, HPGD), leukocyte differentiation (LOC100297044, GCSAML, KLF17), and antimicrobial peptide production (CATHL3, GZMB, LTF) were identified in Healthy cattle. BRD cattle possessed increased expression of CFB, and mRNA related to granulocytic processes (DSG1, LRG1, MCF2L) and type-I interferon activity (HERC6, IFI6, ISG15, MX1). Healthy and Treated_1 cattle were similar in terms of gene expression, while Treated_2+ cattle were the most distinct. ROC cutoffs were used to generate an at-arrival treatment decision tree, which classified 90% of Treated_2+ individuals. CONCLUSIONS: Increased expression of complement factor B, pro-inflammatory, and type I interferon-associated mRNA hallmark the at-arrival expression patterns of cattle that develop severe clinical BRD. Here, we corroborate at-arrival mRNA markers identified in previous transcriptome studies and generate a prediction model to be evaluated in future studies. Further research is necessary to evaluate these expression patterns in a prospective manner.

Multipopulational transcriptome analysis of post-weaned beef cattle at arrival further validates candidate biomarkers for predicting clinical bovine respiratory disease.

Bovine respiratory disease (BRD) remains the leading infectious disease in post-weaned beef cattle. The objective of this investigation was to contrast the at-arrival blood transcriptomes from cattle derived from two distinct populations that developed BRD in the 28 days following arrival versus cattle that did not. Forty-eight blood samples from two populations were selected for mRNA sequencing based on even distribution of development (n = 24) or lack of (n = 24) clinical BRD within 28 days following arrival; cattle which developed BRD were further stratified into BRD severity cohorts based on frequency of antimicrobial treatment: treated once (treated_1) or treated twice or more and/or died (treated_2+). Sequenced reads (~ 50 M/sample, 150 bp paired-end) were aligned to the ARS-UCD1.2 bovine genome assembly. One hundred and thirty-two unique differentially expressed genes (DEGs) were identified between groups stratified by disease severity (healthy, n = 24; treated_1, n = 13; treated_2+, n = 11) with edgeR (FDR ≤ 0.05). Differentially expressed genes in treated_1 relative to both healthy and treated_2+ were predicted to increase neutrophil activation, cellular cornification/keratinization, and antimicrobial peptide production. Differentially expressed genes in treated_2+ relative to both healthy and treated_1 were predicted to increase alternative complement activation, decrease leukocyte activity, and increase nitric oxide production. Receiver operating characteristic (ROC) curves generated from expression data for six DEGs identified in our current and previous studies (MARCO, CFB, MCF2L, ALOX15, LOC100335828 (aka CD200R1), and SLC18A2) demonstrated good-to-excellent (AUC: 0.800-0.899; ≥ 0.900) predictability for classifying disease occurrence and severity. This investigation identifies candidate biomarkers and functional mechanisms in at arrival blood that predicted development and severity of BRD.

Comprehensive at-arrival transcriptomic analysis of post-weaned beef cattle uncovers type I interferon and antiviral mechanisms associated with bovine respiratory disease mortality.

BACKGROUND: Despite decades of extensive research, bovine respiratory disease (BRD) remains the most devastating disease in beef cattle production. Establishing a clinical diagnosis often relies upon visual detection of non-specific signs, leading to low diagnostic accuracy. Thus, post-weaned beef cattle are often metaphylactically administered antimicrobials at facility arrival, which poses concerns regarding antimicrobial stewardship and resistance. Additionally, there is a lack of high-quality research that addresses the gene-by-environment interactions that underlie why some cattle that develop BRD die while others survive. Therefore, it is necessary to decipher the underlying host genomic factors associated with BRD mortality versus survival to help determine BRD risk and severity. Using transcriptomic analysis of at-arrival whole blood samples from cattle that died of BRD, as compared to those that developed signs of BRD but lived (n = 3 DEAD, n = 3 ALIVE), we identified differentially expressed genes (DEGs) and associated pathways in cattle that died of BRD. Additionally, we evaluated unmapped reads, which are often overlooked within transcriptomic experiments. RESULTS: 69 DEGs (FDR<0.10) were identified between ALIVE and DEAD cohorts. Several DEGs possess immunological and proinflammatory function and associations with TLR4 and IL6. Biological processes, pathways, and disease phenotype associations related to type-I interferon production and antiviral defense were enriched in DEAD cattle at arrival. Unmapped reads aligned primarily to various ungulate assemblies, but failed to align to viral assemblies. CONCLUSION: This study further revealed increased proinflammatory immunological mechanisms in cattle that develop BRD. DEGs upregulated in DEAD cattle were predominantly involved in innate immune pathways typically associated with antiviral defense, although no viral genes were identified within unmapped reads. Our findings provide genomic targets for further analysis in cattle at highest risk of BRD, suggesting that mechanisms related to type I interferons and antiviral defense may be indicative of viral respiratory disease at arrival and contribute to eventual BRD mortality.

Whole blood transcriptomic analysis of beef cattle at arrival identifies potential predictive molecules and mechanisms that indicate animals that naturally resist bovine respiratory disease.

Bovine respiratory disease (BRD) is a multifactorial disease complex and the leading infectious disease in post-weaned beef cattle. Clinical manifestations of BRD are recognized in beef calves within a high-risk setting, commonly associated with weaning, shipping, and novel feeding and housing environments. However, the understanding of complex host immune interactions and genomic mechanisms involved in BRD susceptibility remain elusive. Utilizing high-throughput RNA-sequencing, we contrasted the at-arrival blood transcriptomes of 6 beef cattle that ultimately developed BRD against 5 beef cattle that remained healthy within the same herd, differentiating BRD diagnosis from production metadata and treatment records. We identified 135 differentially expressed genes (DEGs) using the differential gene expression tools edgeR and DESeq2. Thirty-six of the DEGs shared between these two analysis platforms were prioritized for investigation of their relevance to infectious disease resistance using WebGestalt, STRING, and Reactome. Biological processes related to inflammatory response, immunological defense, lipoxin metabolism, and macrophage function were identified. Production of specialized pro-resolvin mediators (SPMs) and endogenous metabolism of angiotensinogen were increased in animals that resisted BRD. Protein-protein interaction modeling of gene products with significantly higher expression in cattle that naturally acquire BRD identified molecular processes involving microbial killing. Accordingly, identification of DEGs in whole blood at arrival revealed a clear distinction between calves that went on to develop BRD and those that resisted BRD. These results provide novel insight into host immune factors that are present at the time of arrival that confer protection from BRD.

Effect of a DNA-based immunostimulant on growth, performance, and expression of inflammatory and immune mediators in beef calves abruptly weaned and introduced to a complete ration.

The effect of a DNA immunostimulant on inflammatory and immune responses, performance, and health in calves following abrupt weaning and introduction to a concentrate diet was tested. Sixty-four single source Angus crossbred steers were weaned on day 1 and assigned to receive a DNA immunostimulant (TRT) or saline (CON) on days 0, 2, 4, and 6. On day 0, steers received clostridial and respiratory vaccines and anthelmintic; they were then transported 2 h, allocated to pens (n = 8 per pen), and introduced to total mixed ration. Daily intake, ADG, and feed efficiency were measured. Serum haptoglobin, tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1ß) were assayed by ELISA or AlphaLISA on days 0, 2, 4, 6, 14, and 28; serum-neutralizing antibodies (SNA) to bovine herpesvirus-1 and bovine viral diarrhea virus-1 (BVDV-1) were quantified on days 0, 28, 68, and 135. In a subset of cattle (n = 6 to 8 per treatment group), the percent macrophages and activated gamma delta (γδ) T cells in blood was determined by flow cytometry on days 2 and 6, and expression of mRNA for TNF-α, interferon-gamma (IFN-γ), IL-4, and IL-10 by stimulated blood mononuclear cells was assessed by real-time reverse transcriptase PCR on day 6. After 70 d, cattle were shipped 1,205 km to a feedlot and performance and health were followed. There was a significant effect of time on serum TNF-α, IL-1ß, haptoglobin, and SNA (P < 0.001); the range in concentration among cattle on each day was large. The ratio of IFN-γ to IL-4 expression was significantly higher (P = 0.03) for TRT cattle, suggesting that treatment activated T-helper type 1 cells. There was a trend toward an improved feed conversion (P = 0.10) for TRT steers over the 70-d backgrounding period. There was no effect of treatment on feedlot performance or carcass merit (P > 0.10). During backgrounding, 1 TRT steer died of enterocolitis. In spite of backgrounding, cattle experienced an outbreak of bovine respiratory disease (BRD) in the feedlot and 1 of 31 TRT cattle and 5 of 32 CON cattle died of BRD. The immunostimulant modified some immune responses during backgrounding. Large variability in inflammatory responses during backgrounding indicated that events around weaning induce systemic inflammation that varies substantially among cattle.

Effects of feeding endophyte-infected tall fescue seeds to stocker Angus steers on retail quality attributes of beef strip steaks.

The objective of this study was to determine the effects of feeding endophyte-infected tall fescue seeds to Angus steers during the stocker phase on the quality attributes of beef strip steaks during retail display. Endophyte-infected tall fescue seeds had no effect on steak surface lean color, myoglobin forms, proximate composition, thiobarbituric acid reactive substances, aerobic plate count, pH, activity of superoxide dismutase and metmyoglobin reductase, shear force, and sensory attributes (P ≥ 0.087). However, lightness, redness, oxymyoglobin percentage, and MRA decreased from 45.01, 32.60, 67.61%, and 9.54 µM/min/g, respectively, on d 0 to 40.11, 21.83, 48.95%, and 2.30 µM/min/g, respectively, on d 7 (P ≤ 0.001). Thiobarbituric acid reactive substances were increased by 30% by d 5 (P = 0.015) and APC was increased by 0.5 log CFU/g by d 7 (P ≤ 0.012).

Multidrug resistant Mannheimia haemolytica isolated from high-risk beef stocker cattle after antimicrobial metaphylaxis and treatment for bovine respiratory disease.

Antimicrobial resistance (AMR) in bacterial respiratory pathogens in high-risk stocker cattle has been poorly characterized. The objective of this study was to describe the prevalence of multidrug resistant (MDR; resistance to > 3 antimicrobial classes) respiratory pathogens in 50 conventionally managed stocker cattle over 21 days after arrival. Cattle received tildipirosin metaphylaxis on day 0 and were eligible to receive up to 3 additional antimicrobials for bovine respiratory disease (BRD): florfenicol, ceftiofur and enrofloxacin. Nasopharyngeal swabs were collected on days 0, 7, 14, and 21 for bacterial culture and antimicrobial susceptibility testing using disc diffusion and broth microdilution. Mannheimia haemolytica was isolated from 5 of 48, 27 of 50, 44 of 50, and 40 of 50 cattle on days 0, 7, 14, and 21, respectively. One of 5, 27 of 27, 43 of 44, and 40 of 40 M. haemolytica were MDR on days 0, 7, 14, and 21, respectively. Pasteurella multocida was isolated from 6 of 48 cattle on day 0 and none were MDR; no other pathogens were isolated. Twenty-four cattle required at least one BRD treatment; M. haemolytica was isolated before treatment from 13 of 24 cattle; all were MDR. One hundred-eighteen M. haemolytica isolates were subjected to pulsed-field gel electrophoresis (PFGE); multiple genotypes were identified. Whole genome sequencing of 33 isolates revealed 14 known AMR genes. Multidrug resistant M. haemolytica can be highly prevalent and genetically diverse in stocker cattle; additional research is necessary to determine factors that influence prevalence and the impact on cattle health.

A randomized controlled trial to test the effect of on-arrival vaccination and deworming on stocker cattle health and growth performance.

Our objective was to determine the effect of vaccination and deworming at arrival (d 0) on bovine respiratory disease (BRD) incidence, mortality, and growth of stocker calves. Calves (n=80) were stratified by d -3 weight and fecal egg count (FEC) into 20 pens of 4 calves. Pens were randomly assigned to treatments in a 2×2 factorial design, testing d 0 vaccination (modified-live respiratory virus and clostridial vaccine, or not) and deworming (oral fenbendazole and levamisole, or not). Body weights were measured on days 0, 14, 28, 42, 56, 70, and 85, and FEC were measured on days -3, 28, 56, and 85. Incidence of BRD was greater for d 0 vaccination (RR=3.2), high fever (≥104°F, ≥40°C) at d 0 (RR=6), and higher d -3 FEC (RR=1.2 per 100 epg). Mortality was greater for d 0 vaccination (OR=8.3) and high fever (OR=41.6). Growth was 10.3 lb (4.7 kg) lower for d 0 vaccination, 24 lb (11 kg) and 16 lb (7.3 kg) lower for moderate (103°F to 103.9°F; 39.4°C to 39.9°C) and high fever, respectively, and 17.6 lb (8 kg) lower for each additional BRD treatment a calf received. Deworming was neither beneficial nor detrimental to any health or performance factors. Health and growth performance of stocker calves may be adversely affected by vaccination at arrival, higher arrival FEC, and fever at arrival.

Notre objectif était de déterminer l'effet de la vaccination et de la vermifugation à l'arrivée (j0) sur l'incidence du complexe respiratoire bovin (CRB), la mortalité et la croissance des veaux d'élevage. Les veaux (n=80) ont été stratifiés selon le poids et le compte d'œufs fécaux (COF) à j-3 et placés dans 20 enclos avec chacun quatre veaux. Les enclos étaient assignés aléatoirement aux traitements selon un plan factoriel 2×2 avec la vaccination à j0 (avec ou sans vaccin anti-clostridial avec virus respiratoires vivants modifiés) et la vermifugation (avec ou sans injection orale de fenbendazole et de lévamisole) comme facteurs. Le poids corporel a été mesuré aux jours 0, 14, 28, 42, 56, 70 et 85 et le COF a été fait aux jours −3, 28, 56 et 85. L'incidence du CRB était plus élevée suivant la vaccination à j0 (RR=3.2), lorsque la fièvre était élevée à j0 (≥104°F, ≥40°C) (RR=6) et lorsque le COF était plus élevé à j-3 (RR=1.2 par 100 oeufs par gramme). La mortalité était plus élevée suivant la vaccination à j0 (RC=8.3) et lorsque la fièvre était élevée (RC=41.6). Il y a eu une perte de croissance de 10.3 lb (4.6 kg) suivant la vaccination à j0, une perte de 24.1 lb (11 kg) lorsque la fièvre était modérée (103­103.9°F), une perte de 16 lb (7.3 kg) lorsque la fièvre était élevée et une perte de 17.5 lb (8 kg) pour chaque traitement additionnel contre le CRB reçu par un veau. La vermifugation n'a pas eu d'effet bénéfique ou néfaste sur tous les facteurs reliés à la santé ou à la performance. La santé et la croissance des veaux d'élevage peuvent être affectées négativement par la vaccination à l'arrivée, par un COF initialement élevé et par la fièvre à l'arrivée.