Regression Equations for Determining Body Composition of Young Chicks

Abstract

Whole chick carcasses from three separate studies were analyzed on day 21 posthatching for moisture (freeze-drying), protein (macro-kjeldahl) and fat (ether-methanol extraction). Wide differences in body composition were obtained by feeding purified diets varying in amino acid quantity and quality. Body water concentrations ranging from 58 to 74% resulted in protein concentrations of 14.2 to 19.1% and fat concentrations of 3.0 to 23.7%. Percent body fat (YF) decreased linearly (P<.01) as percent body water (X) increased. The equation describing this relationship was YF= 101.94–1.33X (r2 =.96). Percent body protein (YP) increased linearly (P<.01) as percent body water (X) increased, the resulting linear regression equation being YP = −2.878+0.297X (r2 = .73). It was concluded that determination of body water for use in these equations provides a simple yet reliable means of estimating the concentration of both body fat and body protein in the young chick.