Muscle protein degradation assessed by N-methylhistidine excretion in mature White Leghorn, dwarf broiler and normal broiler males maintained on either low- or high-protein diets (original) (raw)

Protein degradation rates were assessed by the excretion of "-methylhistidine (N'MH) in four strains of mature chickens, two White Leghorns and two broilers (dwarf and normal), fed on diets containing two levels of dietary protein. Over 0.9 of labelled N'MH was recovered within 7 d of injection from three White Leghorn, three dwarf and three normal broiler males. Protein degradation, measured by N'MH output, was related to adult body-weight by the power 071 and strain intercepts were significantly different. Strain differences disappeared when the rate of output of N'MH per unit lean was evaluated. The rate of output of N'MH per unit muscle was higher in birds fed on a low-protein diet of 100 g crude protein (nitrogen x 6.25; CP)/kg compared with males fed on zyxw 150 g CP/kg. It was concluded that the lower rate of protein degradation in broiler compared with layer strains at young ages is related to increased adult body-weight in agreement with well-established biological principles.