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This Article Full Text (PDF) All Versions of this Article: jas.2008-1256v1 87/1/269    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Boles, J.A. Articles by Tess, M.W. Search for Related Content PubMed PubMed Citation Articles by Boles, J.A. Articles by Tess, M.W.

Growth implants reduced tenderness of steaks from steers and heifers with different genetic potentials for growth and marbling

J.A. Boles^*, D. L. Boss, K. I. Neary^*, K.C. Davis^* and M.W. Tess^*

^* Animal and Range Sciences Department, Montana State University, P.O. Box 172900, Bozeman, MT 59717-2900 Northern Agricultural Research Center, 3848 Fort Circle, Havre, MT 59501-8409

jboles{at}montana.edu

Abstract

The objective of this study was to evaluate the effect of growth implants on the carcass characteristics and tenderness of steers and heifers with different genetic potentials for growth, lean meat yield production and marbling. Two experiments were conducted. Experiment 1 evaluated Angus steers sired by bulls with high EPD for retail product yield or marbling. Implant treatment was imposed randomly within sire groups. Loins (IMPS 180) were collected from each carcass and cut into three 2.54 cm steaks aged for 7, 14 and 21 days to evaluate tenderness. The second experiment evaluated steers and heifers of British and Continental breed descent. Steers and heifers were harvested following 120 days on feed. Loin sections were collected and one – 2.54 cm steak aged 7 days was used for tenderness analysis. When implants were used in Angus steers, hot carcass weight and LM area increased while internal fat and marbling decreased (P < 0.01). In Angus steers, sire type did not affect shear force values of steaks however, implant use significantly increased shear force values (P < 0.01). Carcasses from cattle of Continental breed descent were significantly heavier than carcasses of British breed descent with larger LM area, slightly less fat and a lower yield grade (P < 0.01). Also, steer carcasses were heavier than heifer carcasses with larger LM (P < 0.05) but no effect of sex on fat depth, internal fat, yield grade or marbling was observed. No significant interactions were seen between growth implant and breed or between growth implant and sex for shear force values. Shear force values were significantly lower for steaks from steers and heifers of British decent compared to steers and heifers of Continental descent (P < 0.01). Steaks from implanted steers and heifers had significantly (P < 0.01) higher shear force values than steaks from steers and heifers not implanted. Use of growth implants in growing cattle resulted in significantly heavier carcasses weights, larger LM area and reduced internal fat. However, implant use also reduced the amount of marbling along with contributing to reduced tenderness. Complicating the tenderness issue is the increased shear force values reported for heifers as well as steers of Continental breed descent. Use of implants may contribute to tenderness variability because of different animal responses to implants.

Key Words: beef • genetic potential • growth implants • shear force • tenderness