PSV-A-11 The Effect of Days on Feed for Feedyard Performance, Health, Carcass, and Organ Characteristics of Angus X Holstein Heifers

Abstract The objective of this study was to evaluate the effect of days on feed (DOF) on performance, health, carcass, and organ characteristics of composite Angus x Holstein heifers (n = 3,676). At time of arrival (d 0), heifers from a single source were placed into large (~300 animal) pens at two commercial feedlot locations in the Texas Panhandle. At administration of final implant (Revalor® 200; d 240), heifers, within lot, were randomly assigned to one of four smaller pens, creating a block (location A block n = 6, location B block n = 7). Pens within blocks were randomly assigned to treatment (323, 344, 365, or 386 DOF). Data were analyzed using DOF as the fixed effect; block was nested within location as a random effect. Linear and quadratic effects were also tested; pen was experimental unit (n = 52). Heifer DMI did not differ across DOF (P = 0.72). Heifer ADG decreased linearly (1.52, 1.37, 1.31, and 1.27 kg/d; P ≤ 0.01). Heifer HCW (372, 387, 401, and 414 kg), longissimus dorsi muscle area (88.63, 89.55, 90.80, and 91.95 cm2), marbling score (535, 553, 563, and 594) and percentage of Prime QG (6.6, 11.2, 12.8, and 19.0 %) linearly increased (P ≤ 0.01) as DOF increased. Frequency of liver scores (edible, minor, or major abscess) did not change over DOF (P ≥ 0.82). Frequency of ideal heart score linearly decreased with DOF (53.0, 44.3, 25.7, and 15.0 %; P ≤ 0.01). Frequency of YG 3 did not change (P = 0.68), however YG 4 linearly increased with DOF (6.2, 12.0, 14.0, and 22.5 %; DOF P ≤ 0.01). Data collected in this trial indicate that DOF led to increased HCW, LM area, marbling, YG, and QG with minimal changes to DMI or liver scores for Angus x Holstein heifers.