COMBINED EFFECTS OF CLENBUTEROL AND VARIOUS CONCENTRATIONS OF PROTEINON PERFORMANCE OF BROILER-CHICKENS

1. The effects of the beta-adrenergic agonist, clenbuterol (1 mg/kg di et) on the growth and muscle composition in female broiler chickens (1 4 to 32 d of age) fed on diets containing various concentrations of pr otein (220, 240 or 260 g protein/kg) were examined. 2. Body weight gai n over the 18 d period increased linearly with increasing protein inta ke. The rate of gain was significantly higher in clenbuterol-treated c hickens than in control birds. 3. Dietary clenbuterol increased thigh muscle weight and protein concentration of breast and thigh muscle, re gardless of dietary protein content. Protein/DNA ratio in thigh muscle was enhanced by clenbuterol feeding, and the magnitude of difference of the ratio was higher in chickens fed on the 240 and 260 g CP/kg die ts than in those fed the 220 g CP/kg diet. 4. It was concluded that cl enbuterol-treated chickens require increased dietary protein to mainta in maximal growth, and that increased protein consumption is an import ant factor in improving growth in clenbuterol-fed broilers.