Genetic parameters for respiratory disease in feedlot beef cattle

Abstract

Bovine respiratory disease (BRD) is the most common and costly disease of feedlot cattle in the United States (NAHMS, 2000). Bovine respiratory disease is a complex of diseases characterized by many types of infection, each having its own causes, clinical signs and economic implications. Prevalent microbial causes for BRD include viral, bacterial and mycoplasmal. Shipping and processing feedlot calves enhances predisposing causes and increases environmental risk factors. Predisposing causes are generally synergistic and include age, stress, and immunological background. Environmental risk factors include climate, ambient temperature, dust particles, stocking density, humidity, ventilation, and shipping distance. Epidemiological factors include microbial agent(s), mode of transmission, parasite density dependence, infectious period, latent and carrier periods, and virulence. Breeds can differ for BRD incidence in preweaned calves (Snowder et al., 2005). Whether there are genetic differences that affect BRD incidence among feedlot cattle is not known. Therefore, the objective of this study was to characterize genetic factors that influence incidence of BRD in feedlot beef calves.