Basal metabolic rate in growing chicks Gallus domesticus.

Basal metabolic rate (B.M.R.) of broilers and Leghorns was measured to assess whether a fundamental change in B.M.R. has occurred in the two types of fowl. A Haldane respirometer was used to quantitate gaseous exchange over variable periods of time. Data were converted to kcal., and covariance analysis was used as a statistical control of the influence of body weight on B.M.R. Measurements were obtained from hatch to 8 weeks of age in both types of poultry. Broilers were found to have a significantly lower B.M.R. from hatch to 500 g. body weight. Above 500 g. body weight, the B.M.R. of the broilers was not found different from Leghorns. After logarithmic transformation, B.M.R. data were regressed on body weight to compute the exponent b for metabolic equations of the form M = aWb where M = metabolic rate, Wb = metabolically effective body weight, a = a constant of proportionality. The b exponent for growing chicks, 40 to 500 g. body weight, was found to be unity (r = 0.98) for both broilers and Leghorns. For growing chicks up to 500 g., it is recommended that a b of 1.0 be used in place of 0.75 for estimating the metabolic rate of chicks.