Graduate Student Poster Competition

The purpose of this study was to investigate the effect of cimaterol, a p-adrenergic agonist, on muscle Calcium Dependent Proteinase (CDP) activity and the possible relationships between proteolytic activity, cimaterol-induced muscle hypertrophy and meat tenderness. Cimaterol was administrated at 0 or 10 ppm in a complete mixed diet to 28 ram lambs for 3 or 6 weeks. Dietary administration of cimaterol reduced micro-molar (pM) CDP activity in longissimus muscle by 62% (P<.OOl). Total CDP activity was not affected. Cimaterol treatment increased longissimus area 29.5% (P<.OOI), enhanced the growth of semitendinosus, semimembranosus and biceps femoris muscles 26'10, 32.4% and 24.5%, respectively (all P<.OOl) and reduced kidney and pelvic fat 20.9% (P<.035). Cimaterol treatment increased lnstron shear force values of cooked longissimus 14.5% (Pc.05) and 44% (P<.OOl) at 3 and 6 weeks, respectively. The inhibitory effect of cimaterol on pM CDP activity may account for the 25%-35% cimaterol-induced hypertrophy of individual muscles and cause a reduction in postmortem myofibril degradation, contributing to the increased shear force values observed.