Abstract Bovine respiratory disease complex (BRD) is an economically relevant trait in the beef industry, particularly in feedlot production. Post-weaning BRD costs the U. S. feedlot industry as much as 1 billion annually in production losses, which include mortality, treatment costs, additional labor, and decreased performance and carcass quality. While good management practices are effective at reducing the impacts of BRD, little is known regarding animal-specific factors that influence BRD. The objective of this study was to compare the performance of binomial and multinomial logistic regression models in predicting BRD health status. Post-weaning health records were obtained on purebred and crossbred seedstock calves born from 2016 to 2024. After initial cleaning, 4, 779 bulls, steers, and heifers were available for analysis. Breeds represented in the dataset were Angus (AN), Simmental (SM), South Devon (DS), Angus x Simmental (SX), Angus x South Devon (DX), and Angus x Simmental x South Devon (DA). The majority of animals were never treated for BRD and remained healthy through the post-weaning period (n = 3, 241). Most calves treated only required one treatment (n = 1, 315). Additional treatments (n = 200) and respiratory deaths (n = 23) were minimal. For binomial logistic regression, calves were classified as either never receiving treatment (0) or receiving one or more rounds of treatment for BRD (1). For multinomial logistic regression, four levels of health status were considered: never treated for BRD (0), treated once (1), treated two or more times (2), and died of respiratory cause (3). Analyses were performed using R software version 4. 4. 1. Both models included fixed effects of breed, contemporary group, and date of birth as Julian date (DOB). Sex was also included as a fixed effect in the multinomial model. In each case, SM and SX animals tended to be healthier than AN calves (p 0. 05). Compared to AN and DX calves, SX animals had 44. 1% and 55. 6% lower odds of requiring treatment for BRD, respectively. Both models also showed DOB to significantly impact calf health (p 0. 05) and indicated that younger animals had increased odds of more severe BRD. Significant differences in sex were found in the multinomial analysis (p 0. 05), where heifers generally had lower odds of more severe BRD than bulls and steers. McFadden’s pseudo R-squared values were 0. 143 and 0. 162 for binomial and multinomial models, respectively, indicating BRD is likely influenced by additional factors not accounted for in this analysis. This study suggests that breed differences exist in BRD susceptibility, but further work is needed to determine the feasibility of genetic selection to improve cattle health.
Tarochione et al. (Wed,) studied this question.