59 Effects of serial harvest on growth and carcass characteristics of beef x dairy crossbred steers

Abstract Beef x dairy crossbred feedlot steers n = 707; body weight (BW) at initial processing = 148 kg were utilized in a randomized complete block design to evaluate effects of three serial harvest endpoints on growth performance and carcass characteristics. Allocation to treatment occurred after 204 d-on-feed (DOF), at which point steers weighed 484 kg (SEM = 3.2 kg). Treatments consisted of three serial harvest endpoints: 326, 347, and 368 DOF, as measured from initial processing at 148 kg. Twelve pens, with approximately 59 steers/pen and four pens/treatment were utilized. Final BW measured 696, 730, and 744 kg at 326, 347, and 368 DOF, and increased (P 0.01) with DOF. Dry matter intake (DMI) from allocation to harvest did not differ among treatments (11.4 kg/d; P = 0.36). Average daily gain (ADG) from allocation to harvest measured 1.82, 1.79, and 1.64 kg at 326, 347, and 368 DOF, respectively and was greater (P 0.01) at 326 and 347 DOF than at 368 DOF. Feed efficiency (FE) from allocation to harvest measured 0.162, 0.151, and 0.143 at 326, 347, and 368 DOF, respectively and was greater (P 0.01) at 326 and 347 DOF than at 368 DOF. Hot carcass weight (HCW) measured 438, 459, and 472 kg at 326, 347, and 368 DOF, respectively and increased (P 0.01) with DOF. Across the 42-d serial harvest period live and carcass ADG averaged 1.09 and 0.78 kg, respectively, with a carcass transfer of 71.6%. Backfat thickness measured 1.35, 1.63, and 1.47 cm at 326, 347, and 368 d, respectively and was greater (P 0.01) at 347 and 368 d than at 326 d. Marbling score measured 508, 529, and 550 at 326, 347, and 368 DOF, respectively and was greater (P = 0.03) at 368 and 347 DOF than at 326 DOF. Distribution of USDA quality grades (QG) did not differ (P = 0.45) among treatments and averaged 6.3% Prime and 83.1% Choice. Ribeye area and dressing percentage (P = 0.11) did not differ among treatments. Distribution of USDA yield grades (YG) was affected by treatment (P 0.01), with a shift toward more YG 4 and 5 carcasses with increasing DOF. Liver abscess occurrence averaged 62.9% and did not differ (P = 0.61) among treatments. Results from this experiment indicate a BW gain of 1.09 kg/d and a HCW gain of 0.78 kg/d across the 42-d serial harvest period. There were no differences in DMI as DOF progressed but ADG and FE decreased in the longest-fed cattle. Distribution of QG was not affected by DOF, but YG increased with increasing DOF.