Gaseous Metabolism of Leghorns and Broilers during Early Growth: Resting Metabolic Rate , ,

Abstract

Resting metabolic rate (RMR) was measured in male DeKalb 231 × Cornell White Leghorns and Ross × Arbor Acre broiler chicks 0–8 weeks-of-age in a modified Haldane apparatus. Chicks were fed a broiler starter diet containing 22% protein and 3234 kcal/kg metabolizable energy (ME). All determinations were conducted between 0800 and 1200 hr. Feed and water were available ad libitum and lighting was continuous.Metabolic rate (kcal/bird per day) was plotted against body weight for the entire 8-week period and results were analyzed using analysis of covariance. RMR in both broilers and Leghorns was best described by the equation Y = 137.87 W·77 where Y equals kcal/bird-day and W equals weight in kg. RMR of Leghorns was 23% higher over the entire 8-week period. The RMR of broilers was 30% higher than their BMR for week 1 and averaged 18% higher over the entire 8-week period.Body composition and gut content were determined on broilers and Leghorns at weekly intervals for 8 weeks. Body weight of birds used to determine RMR were then corrected for percent fat, moisture, ash, protein, and gut content. Corrected body weights were plotted against RMR to determine which body component was the best predictor of metabolic rate. As the body weight was reduced by correcting for the various components, the slope changed little, while the constant of proportionality increased. Live weight and empty body weight (body weight minus gut content) yielded the highest slope. All equations had high coefficients of correlation, greater than .94.