Two experiments evaluated broiler performance and processing charac-eristics when fed increasing Gly concentrations in reduced (RCP) or low CP (LCP) diets from 0-48 d. Ross 708 male off-sex chicks reared in floor pens (21 birds/pen) were used in experiment 1 (EXP 1; 1,008 chicks) and 2 (EXP 2; 1,260 chicks). EXP 1 included 4 treatments: a control (CTL) diet and a RCP diet (~1.7% unit CP reduction) without or with Gly added to achieve 100 (moderate; M Gly) or 112% (high; H Gly) total Gly+Ser of the CTL diet in each phase. EXP 2 included 6 treatments: a CTL diet, a RCP diet, or a LCP diet (~2.4% unit CP reduction and 88% total Gly+Ser; LCP88) without or with Gly added to achieve 100, 112, or 124% total Gly+Ser of the RCP diet. Both EXP included starter (0-14 d), grower (14- 28 d), and finisher 1 (28-39 d) and 2 (39-48 d) diets with similar digestible essential amino acid levels. Treatments were replicated in 12 pens in EXP 1 and 12 or 9 pens in EXP 2. Dietary nutrients met breeder specifications. Body weight gain (BWG), feed intake (FI), and FCR were evaluated, and 6 birds/pen were randomly selected for processing at 48 d. Data from EXP 1 were analyzed by a 1-way ANOVA and Tukey’s means separation, while data from EXP 2 were analyzed by pre-planned orthogonal, linear, and quadratic contrasts (P≤0.05). In EXP 1, 0-14 d broiler performance was similar (P>0.05) among treatments. From 0-48 d, broilers fed the H Gly diet had the lowest (P=0.006) BWG and highest (P=0.003) FCR. Feeding either the RCP or M Gly diet resulted in growth and processing yields similar (P>0.05) to the CTL. In EXP 2, increasing Gly in the LCP88 diet linearly reduced (P≤0.027) 0-14 d FI and FCR with no effect on BWG. From 0-48 d, broilers had similar (P>0.05) performance when fed the CTL or RCP diets, but had a higher (P<0.001) FCR when fed the LCP88 diet. Increasing Gly linearly reduced (P=0.033) FCR. Total breast meat yield was reduced (P≤0.02) for birds fed the LCP88 diet relative to that of CTL and RCP-fed birds and did not respond to increasing Gly.

Cumulative data from these 2 EXP indicate that Gly needs of broilers reared to market ages may depend upon dietary CP content per se or other dietary changes associated with low CP diets.

Lee, T., J. Lee, C. Ruan and S. Rochell. 2022. Responses of broilers to increasing dietary glycine when fed reduced or low crude protein diets from 0 to 48 days. 2022 International Poultry Scientific Forum, Research Abstract M102.