Date of this Version
Economic losses caused by morbidity and mortality from bovine respiratory disease (BRD) in newly weaned/received cattle are one of the most significant problems facing the beef cattle industry. In small feedlots (100 to 1,000 animals marketed annually) throughout the United States (USDA-APHIS, 1994), death losses ranged from 1.5 to 2.7 per 100 animals marketed, with greater losses in western than in central regions of the US. Two-thirds to three-quarters of these deaths were attributed to respiratory disease (USDA-APHIS, 1994).
Two factors contribute to the high incidence of BRD in newly received, lightweight (e.g., < 400 to 500 lb) cattle. First, stresses associated with weaning and transportation negatively impact the immune system (Blecha et al., 1984) at a time when the animal is often exposed to a variety of infectious agents as a result of marketing procedures. Second, feed intake by stressed calves is typically low (Cole, 1995), averaging approximately 1.5% of BW during the first 2 wk after arrival of lightweight feeder cattle (Galyean and Hubbert, 1995). This low feed, and thereby nutrient, intake may further impair immune function (Cole, 1995). Older (e.g., yearling) cattle typically have greater intake than lightweight cattle subjected to shipping stress, although outbreaks of BRD can still be a problem in older cattle. Practices that have been used to offset these negative factors that impact the health of newly received cattle include preconditioning (Cole, 1993), on-ranch vaccination programs (Parker et al., 1993), nutritional management, and prophylactic medication. This review will emphasize nutritional and prophylactic medication approaches and their effects on performance and health of newly weaned/received beef cattle.