Gaseous metabolism of leghorns and broilers during early growth: existence energy rate

Existence energy rate (EER) was measured on male Ross x Arbor Acre broilers and DeKalb 231 x Cornell White Leghorns from day of hatch to 8 weeks of age. The EER was measured in an open circuit respirometer with feed and water available ad libitum. The log of heat production (kilocalories per bird per day) was plotted against the log for body weight (kilograms) for each type bird. Data from broilers and Leghorns were then compared using analysis of covariance. The equations best describing EER for Ross x Arbor Acre broilers and DeKalb 231 x Cornell White Leghorns were Y = 148W.77 and Y = 110W.74, respectively, where Y equals kcal/bird-day and W equals body weight (kg). There was no significant difference in slope (.77 compared to .74) between the two types of poultry; however, broilers had a significantly higher EER than Leghorns (147 compared to 110) when analyzed at equal body weights. Apparently the greater food intake and activity associated with feeding effected the marked increase in heat production by broilers.