Effects of heifer finishing implants on beef carcass traits and longissimus tenderness.
Effects of finishing implants on heifer carcass characteristics and LM Warner-Bratzler shear force (WBSF) were investigated using commercially fed Continental x British heifers (n = 500). Heifers were blocked by initial BW (block 1, BW > or = 340 kg; block 2, BW < 340 kg) and assigned randomly to 12 treatments that utilized 0, 1, or 2 finishing implants to deliver cumulative dosages of trenbolone acetate (TBA) and estradiol 17-beta (E2) ranging from 0 to 400 mg of TBA and 0 to 40 mg of E2 during the finishing period. Heifers in blocks 1 and 2 were slaughtered after 135 and 149 d on feed, respectively. At these endpoints, the treatment groups did not differ (P > 0.05) in adjusted fat thickness or predicted percentage of empty body fat. Compared with a nonimplanted control, implanting heifers once during finishing increased (P = 0.025) HCW by an average of 7.9 kg without affecting the mean marbling score, the percentage of carcasses grading Choice and Prime, or LM WBSF values. Compared with the use of 1 implant, the use of 2 finishing implants resulted in an additional increase (P = 0.008) in HCW of 6.0 kg. Reimplanting also increased (P < 0.001) LM area, reduced (P = 0.024) the percentage of KPH, and improved (P = 0.004) mean yield grade. However, reimplanted heifers produced a lower (P = 0.044) percentage of carcasses grading Choice and Prime and LM steaks with greater (P < 0.05) WBSF values at all postmortem aging times compared with heifers that were implanted once. Among heifers receiving 2 implants, mean 14-d LM WBSF increased linearly (P < 0.05) as the cumulative, combined dosage of E2 plus TBA increased. Heifers implanted with a combination of E2 plus TBA had larger (P = 0.046) LM areas, lower (P = 0.004) mean marbling scores, and greater LM WBSF values after 3 d (P = 0.001), 7 d (P = 0.001), 14 d (P = 0.003), and 21 d (P = 0.045) of postmortem aging than did heifers implanted with TBA alone. Heifers that received combination implants containing both E2 and TBA also produced fewer (P = 0.005) carcasses with marbling scores of modest or greater compared with heifers that received single-ingredient implants containing TBA alone. Implant treatment effects on LM WBSF gradually diminished as the length of the postmortem aging period increased. Postmortem aging periods of 14 to 28 d were effective for mitigating the detrimental effects of mild or moderately aggressive heifer implant programs on the predicted consumer acceptability of LM steaks.
Schneider
B A
BA
Department of Animal Sciences, Colorado State University, Fort Collins 80523, USA.
Tatum
J D
JD
Engle
T E
TE
Bryant
T C
TC
D000273:Adipose Tissue / Q000187:drug effects; D045930:Anabolic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D008460:Meat / Q000592:standards*; D018482:Muscle, Skeletal / Q000187:drug effects; D011897:Random Allocation; D033081:Shear Strength; D013997:Time Factors; D014204:Trenbolone Acetate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
D045930:Anabolic Agents; D004343:Drug Implants; D004958:Estradiol; D014204:Trenbolone Acetate