An evaluation of the genetic components of bovine respiratory disease and its influence on production traits

Abstract

Bovine respiratory disease (BRD) is among the most important infectious disease facing the entire cattle industry. The economic consequences associated with BRD is significant and is one of the most challenging obstacles facing the profitably of cattle operations. Factors that contribute to respiratory diseases in cattle can be broken down into three different segments: viruses, bacteria, and stress. Due in large part to the structure of the U. S. cattle industry, there is no more critical time period cattle face in terms of the overall health and productivity than at weaning and as animals enter the feedlot. The objectives of this study were threefold: 1) to investigate the effects of BRD incidence and number of treatments on economically important performance and carcass traits. 2) to examine the effects lung lesion scores have on important production traits 3) to evaluate the genetic components associated with BRD in both pre-wean and feedlot cattle. In general, the results of this study agree with previous findings of the effect of BRD incidence on production traits, in which greater frequency of BRD treatment is associated with increasing effects on the traits of interest. In terms of lung lesion scores, the only significant differences in the traits of interest were observed when comparing cattle with and without active bronchial lymph nodes. The heritability for BRD incidences in pre-wean cattle was estimated at 0.12 ± 0.06 and 0.08 ± 0.05 for the number of BRD treatments in the current population. Heritability estimates were 0.07 ± 0.04 for BRD incidence and 0.05 ± 0.04 for the number of treatments in feedlot cattle. Though these estimates are low, genetic improvement may be possible through selection programs geared towards BRD resistance in pre-wean and feedlot cattle. Estimates of the genetic correlations between either health measure with hot carcass weight, rib-eye area,