Bovine respiratory disease (BRD) cause-specific and overall mortality in preweaned calves on California dairies: The BRD 10K study

Abstract

Mortality in preweaned dairy calves is a significant source of economic loss for dairy producers. In particular, bovine respiratory disease (BRD) is a leading cause of death in preweaned dairy calves. The objectives of this study were to investigate management practices and their effects on mortality, both that specifically attributed to BRD and overall mortality due to all causes, in preweaned dairy calves. Rates of failure of passive transfer of immunity (FPT) are also reported. The study consisted of a convenience sample of 5 dairies across California, selected based on management practices, calf records, location, and size. Trained study personnel performed comprehensive calf management surveys on every dairy at least once every season. Calves were enrolled in the study at birth and followed until weaning. Mixed-effect logistic regression models were specified for the outcomes all-cause mortality (any death before weaning) and mortality attributed to BRD. The 2 final models included a total of 11,470 calves that were born on the study dairies and followed until weaning. The study cohort's overall crude mortality was 2.8%, with crude mortality of individual dairies ranging from 1.7 to 7.2%. The proportion of mortality attributed to BRD was 19.3%, with a range of 0 to 27.1% on the study dairies. Increasing the frequency of changing maternity pen bedding was associated with a decreased risk of mortality due to BRD. Calves diagnosed with BRD in the spring had an increased risk of mortality compared with calves born in the summer; mortality in calves with fall and winter BRD diagnoses did not different significantly from that in summer. Season of mortality was not significant in either model. Feeding ≥5.7 L of milk per day per calf (vs. ≤3.7 L/d) decreased the risk of mortality in calves over 21 d of age. Twins had a 68% increased risk of all-cause mortality compared with calves born as singletons. Both mortality models showed an association between administration of a modified live vaccine in dams (targeting BRD pathogens) and a decreased risk of mortality in calves. Using a serum total protein cut-off of 5.2 g/ dL, 16.8% of calves had FPT, with a mean serum total protein concentration of 5.94 ± 0.06 g/dL across all calves sampled.

The Effect of Metaphylactic Use of Tildipirosin for the Control of Respiratory Disease in Long-Distance Transported Dairy Calves

“…The BRD incidence in our study calves was lower than we expected. For instance, two recent studies showed BRD incidences of ∼22% for calves being diagnosed and treated at least once in the first 3 months of age (4,19). It is plausible that the lack of impact of metaphylaxis on BRD incidence might be due to the low BRD incidence and consequently low statistical power of our study.…”

“…According to the United States Department of Agriculture (USDA) National Animal Health Monitoring Survey conducted in 2014, BRD affected 27% of pre-weaned calves and caused 14.1% of deaths (3). Recently, a study performed in California dairies between 2015 and 2016, reported 22.8% BRD incidence in pre-weaned dairy calves totaling 19.3% case fatality rate (4). The short-term economic impact of BRD on farm operations are due to labor (i.e., for disease detection and care of sick animals), medications, veterinary fees, and replacement of dead animals (5,6).…”

Production Significance of Bovine Respiratory Disease Lesions in Slaughtered Beef Cattle

“…Some authors suggested that intensive co-housing boosts the exchange of airborne pathogens and facilitates nose-to-nose contact between calves, potentially increasing the risk of BRD [ 29 , 30 ]. However, in this study, when global data were considered, the highest prevalence rates of subclinical BRD were found in veal calves raised in mixed and extensive management systems.…”

Bovine Respiratory Disease Vaccination Against Viral Pathogens

“…Similarly, overall preweaning dairy heifer BRD-associated mortality is 19%. 43 The level of interference of colostrum-derived immunity at the time of vaccination can similarly affect clinical protection and efficacy of vaccination in dairy calves. Two studies evaluated the effect of vaccination of dairy calves between 3 days and 6 weeks of age, with single or 2 doses of a multivalent MLV vaccine on the natural occurrence of BRD between 1 and 3 months of age.…”