Effect of amino acid formulation and amino acid supplementation on performance and nitrogen excretion in turkey toms

A2 x 2 factorial experiment was conducted to determine whether diets formulated with 2 (Lys and Met) or 3 (Lys, Met, and Thr) supplemental AA to 100 or 110% of NRC (1994) amino acid (AA) recommendations would affect performance and N excretion of turkey toms. Diets were formulated with corn, soybean meal (SBM), and 6% meat and bone meal. Diets were formulated to maximize SBM inclusion when formulated with 2 supplemental AA, thereby resulting in 2.0, 1.5, 1.4, and 1.0% units more CP than diets containing 3 supplemental AA at 4 to 8, 8 to 12, 12 to 16, and 16 to 20 wk of age, respectively. Each diet was fed to 12 replicate pens of birds with 10 birds per pen. Body weight, feed intake, and feed/gain was not affected by AA formulation or AA supplementation (average 20-wkBW= 20.7 kg). Similarly, the weight of the pectoralis major at 20 wk of age was not different between birds fed different diet regimens. Nitrogen intake was affected by diet with birds fed 100% NRC AA consuming 144 g (7.3%) less N, with $0.48 less feed cost/20-wk tom, than those fed 110% NRC AA. Similarly, birds fed 3 vs. 2 supplemental AA consumed 154 g less feed N (8.4%) with $0.37 less feed cost/20-wk tom to 20 wk of age. These differences in N intake resulted in 0.8 kg more N in litter/pen (7%; P = 0.067) in birds fed 100% NRC AA vs. those fed 110% NRC. Similarly, birds fed 3 vs. 2 supplemental AA had 1.24 less N in litter/ pen (10.8%). These data suggest that diets containing AA formulations above NRC (1994) recommendations do not provide any additional performance or pectoralis major yield benefits, yet results in considerable increases in excreted N. In addition, formulation with 3 supplemental AA results in a sizeable reduction in N consumed and excreted.