Case study: Effects of undifferentiated bovine respiratory disease on performance and marbling deposition in feedlot steers fed to a common yield grade endpoint

Author: Daniel U. Thomson, Eric S. Moore, Brad J. White, Chris D. Reinhardt

Abstract: A total of 202 Angus steers with an average body weight (BW) of 678 ± 73 lb (308 ± 33.2 kg) were used to evaluate the effects of undifferentiated bovine respiratory disease (BRD) on feedlot performance and carcass
quality in cattle marketed at a common yield grade endpoint. Calves were fed in a single pen in a commercial feedyard. Individual weights were collected on arrival, at 75 days on feed, and immediately prior to shipment at time of harvest. Cattle were harvested in three different groups based on day 75 BW and ultrasound evaluation: 122, 156, or 178 days on feed. Cattle treated two or more times weighed less upon feedlot arrival, had greater mortality, lower average daily gain (ADG), lower day 75 BW, and less external fat deposition on day 75 than cattle not requiring treatment for BRD (P < 0.05). Overall ADG was lower for cattle requiring either one or two or more treatments compared to cattle requiring no treatments; however, ADG from day 75 through harvest was similar among cattle requiring zero, one, and two or more treatments. There was no effect of BRD treatment on hot carcass weight, carcass quality, or yield grade (P > 0.05). Lengthening the feeding period to attain a comparable body composition for cattle that were treated for BRD, compared to cattle never treated for BRD, resulted in similar quality grades.