Effect of amino acid formulation and supplementation on nutrient mass balance in turkeys

Nutrient mass balances were determined for turkeys fed 4 diets in a 2 × 2 factorial design to investigate the effects of diets with 100 or 110% of NRC (1994)-recommended amino acid (AA) formulation and diets containing 2 (Lys and Met) or 3 (Lys, Met, and Thr) supplemental AA. Hybrid tom turkeys were raised and monitored in 12 rooms (3 replicates/diet; 20 toms/room at hatch, culled to 16 at 21 d and then to 12 at 28 d of age). All feed and litter entering and leaving the rooms were quantified and analyzed for nutrient content. Air emissions were measured throughout the 20-wk study. The 100% NRC diets resulted in lower cumulative loss of NH(3) (by 14%) and H(2)S (by 21%) as compared with the 110% NRC diets. Reductions corresponded to lower N and S intake. Feeding the 3 supplemental AA diets resulted in lower N excretion (by 12%) and lower cumulative loss of NH(3) (by 23%) as compared with the 2 supplemental AA diets. The NH(3) emission as a percentage of N output was not significantly influenced by dietary CP (100 vs. 110% of NRC); however, the 3 supplemental AA diets resulted in less NH(3) emitted as a percentage of N output as compared with the 2 supplemental AA diets (9.9 vs. 11.8%). Across all 4 diets, N partitioning averaged 31.4, 56.9, and11.4% for retention, excretion, and air emission, respectively. The N loss estimated from the mass balance approach (9.6%) was comparable with the measured N loss as air emission (11.9%). Partitioning of P averaged 31.9 and 68.1% for retention and excretion, respectively. Partitioning of S averaged 27.5, 72.1, and 0.5% for retention, excretion, and air emission, respectively. The results illustrated the fate of N, P, and S in a turkey production system and demonstrated the potential for reducing nutrient excretion and air emissions from turkeys through diet modification of AA.