Energy partitioning in male growing turkeys.

Feed is one of the most important cost factors in poultry production, and energy represents the largest fraction of this cost. Surprisingly little is known about the energy utilization in turkeys. A better understanding of the energy utilization by growing turkeys may contribute to improve the efficiency of nutrient and energy utilization. The objective of the present study was to quantify the change in energy utilization in male turkeys during growth. Energy and nitrogen balances were performed in a respiration chamber in medium-type male turkeys to partition ME intake between heat production (HP) and energy retention as protein and lipid. The measurements consisted of 7-d balance periods during which the turkeys were offered feed ad libitum during 6 d, followed by 1 d of fasting. Total HP was partitioned into fasting HP, activity-related HP, and thermic effect of feeding. Results of the components of ME utilization were analyzed by ANOVA. Also, the maintenance energy expenditure and efficiencies of energy utilization were estimated by multiple regression analysis. Feed intake and growth were in line with the recommendations of the breeder. Fasting HP was proportional to BW raised to the power 0.75. The ME intake decreased with increasing BW and HP increased from 53 to 64% of ME intake at 0.5 and 13.5 kg of BW, respectively. The fasting HP represented the largest part of HP and averaged 449 kJ.(kg of BW)(-0.75).d(-1). The activity-related HP accounted for 9.1% of ME intake, whereas the thermic effect of feeding decreased with increasing BW and ranged from 17.9 to 14.5% of ME intake. Energy retained as protein decreased with increasing BW from 67 to 37% of energy retention. The maintenance energy expenditure was estimated at 641 kJ.(kg of BW)(-0.75).d(-1), whereas energy efficiencies for protein and lipid retention were 65 and 100%, respectively. This study contributes to the understanding of the changes in energy utilization in turkeys during growth.