The continuous development of accurate and precise methods for measuring energy is vital in the modern poultry industry. The classical method of net energy (NE) assesses the value of ME minus heat increment (HI). Previous research shows increasing amino acid levels increases body protein but also heat production (HP), while increasing ME increases body fat but lowers heat production. Classic NE can be misleading as more calorie efficiency is given to fat deposition than lean mass deposition. Therefore it’s desirable to provide an improved process of calculating NE based on body composition plus and HP (Ark NE). Three test diets were developed for each feeding phase, with two different samples of soybean meal (SBM) or corn. Diets were evaluated for starter (0-10d, 3,008 kcals ME/kg, 21%CP), grower (10-22d, 3,100 kcals ME/kg, 19%CP) and finisher (22-42d, 3,200 kcals ME/kg, 18%CP). The highest concentration of lysine/CP/kcal for each ingredient was utilized as control ingredient. The control ingredient was formulated in a corn soybean diet to provide 80, 100 and 120% AA requirements for each phase with both AA levels and ME set according to the breeder recommendation. Each of the SBM or corn samples were fed equally on a percentage basis as determined for the control SBM and corn. Heat production (HP) kcal=3.872*VO (L/d) + 1.195 VCO2 (L/d, Farrell, 1974) was measured for 1d. Fasting heat production (FHP) was measured for 1d. HI was determined HI=HP – FHP (Farrell, 1974). Body composition was measured throughout the experiments by dual energy X-ray absorptiometry (DEXA) to determine net energy gain (NEg). The objective of these studies is to determine the effect of ingredient quality (digestible nutrient content) on NEg and HP (NE maintenance) while comparing the Classic NE and Ark NE calculations. As quantity of AA increased in SBM, HP and protein:fat ratio increased indicating a positive correlation (R2=0.94). However, as the quantity of AA decreased in corn, HP and protein:fat ratio decreased indicating a negative correlation (R2=0.99).
Based on the finding in the current study, HP is mainly impacted by SBM AA, however when additional corn is added HP becomes diluted, making the Classic NE system misleading.