Effects of days on feed and growth implant administration on live growth performance, live and carcass biometric measures, and carcass grading outcomes

Abstract

Objective: We evaluated the effects of growth implant administration upon live growth performance, dimension- al growth, and carcass outcomes of steers across a 378-d feeding duration. Materials and Methods: Charolais × Angus steers (n = 80; BW 271 ± 45 kg) were allocated to implant (REV; Revalor-XS; on d 0 and 190) or nonimplanted con- trol (CON) and slaughter date (1, 42, 84, 126, 168, 210, 252, 294, 336, and 378 d on feed [DOF]) in a 2 × 10 facto- rial experiment. Live biometric measures were recorded at each slaughter period, and individual feed consumption was recorded daily. Four pairs of animals were processed on each slaughter day; after a 48-h chill, carcasses were assessed for dimensions and graded. Data were analyzed via mixed models to test the fixed effects of DOF and treatment. Results and Discussion: Average daily gain and G:F were 10% and 7.7% greater (P < 0.01) for REV steers compared with controls. Body width (+2.2%), maximal carcass width (+4.5%), and carcass surface area (+4.2%) were greater for REV steers. Implanted steers had a 6.5% heavier hot carcass weight, 0.7 percentage point greater dressed carcass yield, 6% larger LM area, and 0.57 percent- age point less KPH; marbling scores did not differ. Live growth performance (ADG, G:F, DMI as a percentage of BW) decreased in a quadratic trend, whereas measures of size and mass (BW, hip height, carcass area) increased quadratically as DOF increased. Additionally, carcass fat outcomes (12th rib fat depth, percentage KPH, YG, mar- bling score) increased at linear, quadratic, or exponential rates from 0 through 378 DOF. Implications and Applications: Live growth per- formance, dimensional growth, and carcass grading outcomes were affected by implant administration and finishing duration. These data can aid producers with marketing and management decisions of beef cattle fed in confinement.