Dietary glycine needs of broiler chicks.

Dietary Gly might become a limiting factor in all-vegetable diets fed to broiler chicks when low CP is formulated in combination with marginal levels of dietary Thr and Ser. A study was conducted to evaluate dietary Gly needs of broiler chicks. Day-old Ross 508 male chicks were placed in 32 floor pens (15 chicks/pen). Chicks were fed a common prestarter diet from 0 to 7 d of age and then fed a diet that contained progressive amounts of dietary Gly ranging from 0.62 to 1.22% from 7 to 20 d of age. Treatment effects were observed for weight gain and feed conversion. Chicks responded in a quadratic manner to supplementation with dietary Gly. The dietary Gly level necessary to support maximum growth and feed conversion for the chick from 7 to 20 d of age was estimated to be at 0.98 (1.76% Gly + Ser) and 1.02% (1.80% Gly + Ser), respectively. Plasma Thr and Ser were unaffected by Gly supplementation, but plasma free Gly increased linearly. Dietary Gly may need to be considered as a limiting nutrient in early nutrition, especially if CP is low, and only vegetable ingredients are being used.