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

Abstract

Ten crossbred (Suffolk X 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 less than .05) and 14%, respectively, in the CIM-fed group. CIM also improved (P less than .01) dressing percent by 4.9 percentage points and improved yield grade by one grade. CIM increased longissimus muscle (LD) area 38% (P less than .01) and the yield of four lean cuts 28% (P less than .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 micron 2 as compared with 1,391 and 1,296 micron2 of the control group, respectively. The increase was approximately 50% (P less than .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 (micrograms/g wet muscle or microgram/g protein) of CIM muscle was much lower (P less than .01) than that of control muscle, suggesting that the protein accretion in muscle was accomplished without additional incorporation of nuclei from satellite cells.

Nutritional and hormonal control of skeletal-muscle cell growth and differentiation

“…The muscle hypertrophy exhibited is believed to occur through increased fibre diameter, with no proliferation of satellite cells. Indeed, muscle DNA concentration (pg/g protein) is sometimes less in treated muscles than in control muscles (Kim et al 1987). The predominant mechanism of action of these agents is thus believed to be a reduction in protein degradation, although protein synthesis has also been shown to be stimulated in some studies (Dawson et al 1991).…”

Nutritional and developmental effects on the intrinsic properties of muscles as they relate to the eating quality of beef

“…Hypertrophy of type IIb fibres relative to type IIa and type I has been a consistent observation in muscle of animals treated with β-agonists (Hamby et al 1986;Maltin et al 1987) without an increase in DNA content (Beermann et al 1987;Kim et al 1987). These changes are associated with reduced myofibrillar proteolysis through reduced calpain activity in vivo and carry over into reduced rates of myofibre fragmentation in post mortem muscle (McDonagh et al 1999).…”

Effect of Different Zilpaterol Hydrochloride Levels and Feeding Methods on the Growth Performance, Carcass Traits and Blood Parameters of Male Japanese Quails During Two Weeks of the Finishing Period

“…Moody et al (2000) mentioned that the β-AA compounds differ in potency, since cells and tissues vary in expression of β-adrenergic receptor types, and in consequence, their effects are also associated with the type of β agonist, species treated, and dose and duration of treatment. In this regard, Kim et al (1987) reported that cimaterol, a β-AA, improved the Effect of Different Zilpaterol Hydrochloride Levels and Feeding Methods on the Growth Performance, Carcass Traits and Blood Parameters of Male Japanese Quails During Two Weeks of the Finishing Period daily gain of lambs during the first 6 weeks of rearing, whereas Pringle et al (1993) found that L644,969, a type ofβ-AA, improved daily gain of lambs only during the first 2 weeks, and dressing percentage during the first 4 weeks of feeding.…”