Effect of the Repartitioning Agent Cimaterol on Growth, Carcass and Skeletal Muscle Characteristics in Lambs

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Abstract
Ten crossbred (Suffolk × Rambouillet) whether lambs were randomly assigned to receive 0 or 10 ppm cimaterol (CIM) in a completely mixed high-concentrate diet for 8 wk. Total weight gain and feed efficiency were improved 29% (P<.05) and 14%, respectively, in the CIM-fed group. CIM also improved (P<.01) dressing percent by 4.9 percentage points and improved yield grade by one grade. CIM increased longissimus muscle (LD) area 38% (P<.01) and the yield of four lean cuts 28% (P<.01). No difference was found in the proportion of type I (slow-contracting, oxidative) and type II (fast-contracting, mixed glycolytic/oxidative) fibers in LD and semitendinosus (ST) muscles between control and CIM groups, indicating no change in fiber type. The cross-sectional area of type II fibers in LD and ST muscles of the CIM group was 2,081 and 1,951 µm2 as compared with 1,391 and 1,296 µm2 of the control group, respectively. The increase was approximately 50% (P<.01). No difference was found in cross-sectional area of type I fibers, indicating that the increase of muscle mass was due to hypertrophy of type II fibers only. DNA concentration (µg/g wet muscle or µg/g protein) of CIM muscle was much lower (P<.01) than that of control muscle, suggesting that the protein accretion in muscle was accomplished without additional incorporation of nuclei from satellite cells. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.

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