title: Effects of glycine supplementation at varying levels of methionine and cystine on the growth performance of broilers fed reduced crude protein diets.
abstract: Two experiments were conducted to investigate Gly addition to reduced crude protein corn-soybean meal (C-SBM) diets with varying levels of TSAA achieved by varying Met and Cys. The experiments were conducted with female Ross 708 broilers in brooder batteries from 0 to 18 d posthatching. Treatments had 6 replicates with 6 broilers/pen. Diets in all experiments were fed without or with Gly supplementation to contain 2.32% total Gly + Ser. All diets were C-SBM based and formulated to contained 1.27% standardized ileal digestible Lys supplemented with 0.20% Lys (0.394% Lys·SO(4)) and to meet or exceed the requirement of all nutrients except Met and Cys where appropriate. Experiment 1 consisted of 8 dietary treatments. Three ratios of Met to Cys (60:40, 50:50, and 40:60) were used on a mole for mole basis to achieve 0.063 mol of TSAA/kg of feed and a positive control with Met:Cys of 50:50 at 0.76 TSAA:Lys. Glycine supplementation did not affect ADG or ADFI; however, G:F was increased (P = 0.003) with Gly supplementation. An increase in Cys and a decrease in Met resulted in a decrease (P = 0.028) in ADG but had no effect on ADFI or G:F. In experiment 2, Met was kept constant at a marginal level of 0.45% and Cys was increased in 0.05% increments from 0.35 to 0.50%. Glycine supplementation had no main effect on ADG, ADFI, or G:F; however, Gly increased G:F at the lower levels of Cys but not at the higher levels (Gly × Cys, P = 0.031). A linear decrease (P = 0.071) was found in ADFI with increasing Cys supplementation. These data indicate that Gly increased G:F in female broilers fed suboptimal levels of Met and Cys but not at Cys levels at or above the requirement. This implies that the synthesis of Cys accounts for a portion of the increased G:F observed from Gly supplementation in female broilers fed reduced CP C-SBM diets.
authors.affiliation: School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Powell
authors.forename: T D
authors.initials: TD
authors.lastname: Bidner
authors.forename: L L
authors.initials: LL
authors.lastname: Southern
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002645:Chickens / Q000254:growth & development*; D003553:Cystine / Q000008:administration & dosage / Q000494:pharmacology*; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005998:Glycine / Q000494:pharmacology*; D008715:Methionine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D004044:Dietary Proteins; D003553:Cystine; D008715:Methionine; D005998:Glycine