The interactive effects of glycine, total sulfur amino acids, and lysine supplementation to corn-soybean meal diets on growth performance and serum uric acid and urea concentrations in broilers.

Four experiments were conducted to determine the interactive effects of Gly, TSAA, and Lys in corn-soybean meal diets on growth performance of broilers. All experiments were conducted with female Ross x Ross 308 or 708 broilers in brooder batteries from 0 to 18 d posthatching. Treatments had 5 to 8 replications with 5 or 6 broilers per replicate pen. Diets in all experiments were fed without or with Gly (2.32% total Gly + Ser). All diets contained 0.25% l-Lys.HCl except in experiment 1, where no crystalline Lys was added. In experiment 1, the total dietary Lys level was 1.26% with TSAA:Lys of 0.72 and 0.76. Increasing TSAA:Lys increased (P < 0.07) G:F. The main effect of Gly was not significant for ADG, ADFI, or G:F; however, G:F was increased by Gly in broilers fed 0.72 but not in those fed 0.76 TSAA:Lys (Gly x TSAA:Lys, P < 0.03). In experiment 2, the total dietary Lys level was 1.26% with TSAA:Lys of 0.51, 0.68, 0.72, and 0.76. Glycine addition did not affect ADG, ADFI, or G:F; however, increasing TSAA:Lys linearly increased (P < 0.01) ADG, ADFI, and G:F and the response was quadratic for ADG and G:F. Experiment 3 was similar to experiment 2 except the total dietary Lys level was 1.35%. Glycine addition increased (P < 0.03) G:F and decreased (P < 0.04) serum uric acid (SUA) and serum urea N concentrations. Also, increasing TSAA:Lys linearly and quadratically (P < 0.02) increased ADG, ADFI, and G:F. In experiment 4, broilers were fed 2 levels of total dietary Lys (1.26 and 1.35%), 3 levels of TSAA:Lys (0.72, 0.76, and 0.80), and without or with Gly supplementation up to a total of 2.32% Gly + Ser. Glycine addition increased ADG (P < 0.02) and G:F (P < 0.01). The increase in G:F with Gly was not the same for all TSAA:Lys (Gly x TSAA:Lys, P < 0.07). Increasing Lys increased (P < 0.01 to 0.10) ADG, ADFI, and G:F. Glycine addition increased ADG and ADFI more in broilers fed 1.35% Lys than in those fed 1.26% Lys (Lys x Gly, P < 0.09). Glycine addition increased SUA in broilers fed 1.26% Lys but decreased SUA in broilers fed 1.35% Lys (P < 0.01). Glycine addition decreased SUA in broilers fed the TSAA:Lys of 0.80 but not at the other TSAA:Lys (P < 0.08). These data indicate that Gly increased G:F and decreased SUA in diets with 1.35% Lys and excess TSAA.