Whole-body protein turnover in chicks at early stages of growth.

Changes in whole-body protein turnover rate in young chicks were measured during very early stages of chicken growth. Day-old single comb White Leghorn male chicks were fed an adequate purified diet. Whole-body protein turnover was determined weekly for 4 wk. Fractional rates of protein synthesis (percent/day) in the whole body decreased from 1 to 4 wk of age while those of degradation remained unchanged. When expressed in terms of body weight per se, no significant change in absolute protein turnover rate (grams/day) was found during the experimental period; however, when expressed in terms of metabolizable body weight (kilograms 0.75), turnover rates increased slightly. Thus, during the first 4 wk of life no decrease in the whole-body protein turnover rate was found in chickens on the basis of units or metabolic body size. Twenty to 28% of the total heat production was accounted for by the energy expenditure due to whole-body protein synthesis.