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Effects of Zeranol-Implantation Periods on Palatability of Longissimus Steaks from Young Bulls and Steers^1,2,

Kansas State University, Manhattan 66506

Abstract

Fifty-five fall-born, Simmental-crossbred, male calves were allotted at birth to one of five treatments: bulls castrated at 5 mo and implanted from birth to slaughter (ST); bulls implanted from birth to slaughter (BI·BS); bulls implanted from birth to weaning (BI·BW); bulls implanted from weaning to slaughter (BI·WS) and non-implanted control bulls (CB). Implanted calves received 36 mg of zeranol at approximately 10O-d intervals. Calves were fed a high-concentrate diet from 8.1 mo of age to an average slaughter age of 17 mo. Longissimus steaks (LS) were evaluated for palatability traits by both a trained sensory panel (TSP) and a take-home consumer panel (CP). Conclusions from both panels were similar. The TSP found LS from ST to be juicier (P<.05) than LS from all bull groups, and to be more tender (P<.O5) than LS from BI·BW and BI-WS. The CP found LS from ST to be juicier, more tender and more acceptable (P<.05) than LS from BI·BW, BI·WS and CB. Steaks from BI·BS were more tender (P<.05) than LS from BI·WS and CB. Steaks from BI·BS and BI·BW had lower (P<.05) shear values than LS from CB, but LS from ST had lower (P<.05) shear values than LS from all bull groups. Blood serum samples taken prior to slaughter and LS from eight cattle from each of the ST, BI·BS and CB treatment groups were used to determine serum testosterone, heat-labile (soluble) and total LS collagen, respectively. Steaks from ST had higher (P<.05) soluble collagen percentages than LS from BI·BS and CB. Serum from ST had lower (P<.05) T levels than serum from both bull groups. Implanting bulls from birth to slaughter was the only effective zeranol-implanting program that improved LS palatability to a level that approached that of LS from implanted ST.

¹ Contribution no. 87-56-J, Dept. of Anim. Sci. and Ind., Kansas Agr. Exp. Sta., Manhattan 66506.

² The authors are grateful to Ecco Ranch, Buffalo, KS for their cooperation in this research.

³ Present address: Coop. Ext., Washington State Univ., Pullman 99164-6310.

⁴ Present address: Int. Brangus Assoc, San Antonio, TX 78290.

⁵ Present address: Dept. of Anim. and Range Sci., Montana State Univ., Bozeman 59717.