Journal of Animal Science, Vol 71, Issue 3 636-644, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Effects over time of feeding a beta-adrenergic agonist to wether lambs on animal performance, muscle growth, endogenous muscle proteinase activities, and meat tenderness

T. D. Pringle, C. R. Calkins, M. Koohmaraie and S. J. Jones
Department of Animal Science, University of Nebraska-Lincoln 68583-0908.

Forty wether lambs were used in a 2 x 4 factorial arrangement to determine the response of animal performance, muscle growth, proteinase activity, and meat tenderness to beta-adrenergic agonist (BAA) supplementation. Lambs were fed a finishing diet with or without 4 ppm of L644,969 and slaughtered after 0, 2, 4, and 6 wk of treatment. The ADG was higher (P < .05) in the treated than in the control lambs after 2 wk and returned to control levels thereafter. Semitendinosus weight and calpastatin activity were higher and mu-calpain activity was lower in the treated than in the control lambs after 2, 4, and 6 wk. Cathepsin B activity was higher (P < .01) and cystatin-like activity was lower (P < .05) after 2 wk in treated than in control lambs but returned to control levels thereafter. Longissimus protein:DNA was higher after 4 (P < .05) and 6 (P < .01) wk in the treated lambs than in the controls. The concentration of RNA and RNA:DNA ratio were higher (P < .01) in the longissimus and semitendinosus muscles in the treated lambs after 2 wk and remained higher throughout the study. Semitendinosus protein and RNA content were higher after 2, 4, and 6 wk and DNA content was higher after 2 and 6 wk in the treated than in the control lambs. Longissimus shear-force values were higher (P < .001) in the treated than in the control lambs at all slaughter end points. These data indicate a rapid alteration of muscle growth, activity of the calpain-calpastatin system, and meat tenderness during BAA treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

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