A FIELD INVESTIGATION OF THE ECONOMIC-IMPACT OF RESPIRATORY-DISEASE IN FEEDLOT CALVES

A trial involving 512 beef calves was conducted in a commercial resear ch feedlot to determine the effect of bovine respiratory disease (BRD) on performance parameters and carcass characteristics. Two hundred an d fifty-six calves that were deemed to be ''sick'' (S) from BRD were a llocated to 16 pens and 256 calves that were considered to be ''well'' (W) were allocated to another 16 pens. The outcome variables that wer e measured included average daily gain (ADG), daily dry matter intake (DDMI), dry matter intake to gain ratio (DM:G), BRD treatment rate, de ath loss, carcass traits, and net profit per pen. The data were partit ioned into several time intervals including processing (P) to day -1, day 0 to day 27, day 28 to day 55, day 56 to day 83, day 84 to day 111 , day 112 to day 139, day 140 to slaughter, day 0 to slaughter (0-Slau gh), and processing to slaughter (P-Slaugh). However, the most importa nt interval was from processing to slaughter. For the interval P-Slaug h, there were no significant (p greater-than-or-equal-to 0.05) differe nces between the S and W groups with respect to ADG and DM:G. Also, fo r the interval 0-Slaugh, the DDMI was similar for both groups. There w ere no significant (p greater-than-or-equal-to 0.05) differences betwe en the S and W groups for carcass weight, average fat, grade fat, rib eye area, marbling score, cutability estimate, or carcass grade distri bution. The BRD treatment rates in the S and W groups were 6.6% and 4. 7%, respectively. The mortality rates in the S and W groups were 0.78% and 0.39%, respectively. Also, there were no deaths attributable to B RD in either group. In the economic model, there was no significant (p greater-than-or-equal-to 0.05) difference between the S and W groups with respect to net profit per pen. We conclude that this trial did no t validate the concept that BRD impacts performance parameters, becaus e a sufficient disease challenge was not present. However, this study provides several observations that will enhance the experimental desig n of future studies that attempt to quantify the total economic impact of BRD.