Effect of bovine respiratory disease during preconditioning on subsequent feedlot performance, carcass characteristics, and beef attributes1,2

Heifers with expected increased risk of bovine respiratory disease (BRD; n = 360; initial BW = 241.3 +/- 16.6 kg) were assembled at a Kentucky order-buyer facility and delivered to Stillwater, OK, in September 2007 to determine the effects of clinical BRD observed during preconditioning on subsequent feedlot performance, carcass characteristics, and meat attributes. During a 63-d preconditioning period, morbidity and mortality attributed to BRD were 57.6 and 8.6%, respectively. Immediately after preconditioning, heifers were grouped according to health outcome category and allotted to finishing pens (5 to 7 heifers/pen). Heifers were never treated for BRD (0X; n = 9 pens), treated 1 time (1X; n = 9 pens), 2 times (2X; n = 6 pens), 3 times (3X; n = 6 pens), or designated as chronically ill (CI; n = 2 pens). Arrival BW was not different (P = 0.21) among treatment categories. However, disease incidence during preconditioning decreased (P < 0.001) growth, resulting in BW of 318, 305, 294, 273, and 243 kg for 0X, 1X, 2X, 3X, and CI, respectively, at the start of the finishing phase. Estimates on the LM, taken by ultrasound on d 65 and 122, were combined with BW and visual appraisal to target common average endpoint within category and block. On average, heifers were slaughtered on d 163 for 0X, 1X, and 2X, d 182 for 3X, and d 189 for CI (P < 0.01). Final BW was similar (P > or = 0.18) for heifers treated 0, 1, 2, or 3 times, but heifers deemed CI weighed less (P = 0.01) than 3X heifers. Considering the finishing phase only, ADG was linearly increased (P < 0.001) with increasing BRD treatments, but was linearly decreased (P = 0.003) as BRD treatments increased from arrival to slaughter. Therefore, G:F was greater (P = 0.007) for CI than 3X and linearly increased (P = 0.002) from 0X to 3X. Similar to BW, HCW was less (P = 0.03) for CI than 3X. Marbling score tended (P = 0.06) to decrease linearly as the number of treatments increased, but no other differences (P > or = 0.24) in carcass traits were detected. No differences were observed in beef tenderness (P = 0.65), and no consistent trends were noted in retail display or palatability data. Less than 20 additional days on feed were required for heifers treated 3 times to have similar BW and carcass characteristics to heifers never treated for BRD. Segregating animals with multiple BRD treatments and feeding them to an acceptable carcass endpoint may be a viable strategy for increasing value of animals treated for BRD.