PSVIII-9 An aggressive implant program altered USDA yield and quality grade of long-fed Jersey steer carcasses

Abstract

Abstract Jersey steers are known for superior marbling, however, due to the late-maturing nature of the breed, require prolonged feeding to reach market weight. This, together with light muscling and excess internal fat, makes Jerseys financially unattractive to the cattle feeding industry. Growth promoting implants, however, may alter nutrient partitioning away from fat accretion toward lean muscle development. We hypothesized that a repeated implant program of Revalor-200 (200mg trenbolone acetate/20mg estradiol) would improve the growth efficiency of Jersey steers. The objective of this study was to evaluate the effect of an aggressive implant program on USDA quality (QG) and yield grade (YG). Jersey steers (n = 27) were fed for 420 d and randomly assigned to one of two treatments: no implant (CON) or administration of Revalor-200 every 70 days throughout the feeding period (IMP). Steers were slaughtered on day 421 and chilled carcasses were graded. Results were analyzed using an independent t-test. An 11% increase (P = 0.01) in HCW occurred for IMP over CON steers. No differences (P ≥ 0.31) were detected in 12th rib fat depth, or LM area per 100 kg of live weight. However, LM area was 10.3 cm2 (P = 0.03) larger and KPH weighed 4.68 kg (2.5%) less (P < 0.01) in IMP vs. CON steers, resulting in a decreased (P < 0.01) USDA YG of 2.97 in IMP steers vs 3.75 in CON steers. Skeletal maturity was not affected (P = 0.12) by implant program. Aggressive implanting caused lean maturity to increase slightly within the A maturity classification (P = 0.02; A73 vs A96) but sharply decreased marbling score (P < 0.01; Moderate80 vs Small20). In summary, repeatedly implanting long-fed Jersey steers may improve carcass cutability; however, it appears to be detrimental to carcass quality grade.