Effects of dietary tryptophan levels on performance and biochemical variables of plasma and intestinal mucosa in yellow-feathered broiler breeders.

The effects of dietary tryptophan (Trp) levels on performance and biochemical variables of plasma and intestinal mucosa in broiler breeder hens were investigated in this study. A total of 780 Lingnan yellow-feathered broiler breeder hens were randomly assigned in one of five dietary treatments with six replicates per treatment (26 birds per replicate). The breeder hens were fed either the basal diet (0.11% Trp) or the basal diet supplemented to 0.15%, 0.19%, 0.23% and 0.27% Trp, from 197 to 259 days of age. Graded levels of Trp from 0.11% to 0.27% in the diet produced quadratic (p < .05) responses in laying rate, average daily egg production, and feed conversion ratio, and quadratic (p < .01) responses in total large follicle weight and average large follicle weight. An increase in fertilization rate of total eggs was observed in breeders fed 0.27% Trp, and hatchability was higher in breeders fed 0.23% and 0.27% Trp than with 0.19% Trp (p < .05). The content of uric acid N decreased with 0.15% and 0.23% dietary Trp (p < .05). The content of GSH and the GSH-to-GSSG ratio in plasma were reduced by 0.15%, 0.19% and 0.27% Trp diets (p < .05). A higher activity of GST in plasma was observed with 0.15% Trp in relation to 0.23% and 0.27% Trp (p < .05). The activity of Na+ -K+ -ATPase of plasma in birds fed 0.27% Trp was lower than in those fed 0.15% Trp and the control birds (p < .05). There were significant influences of dietary Trp levels on S6K1, B0 AT1, Nrf2, TLR4, TNF-α and IL-6 transcripts of ileal mucosa (p < .05). The optimal dietary Trp level was 0.203% or 254 mg per hen per day, for Chinese yellow-feathered broiler breeder hens aged from 197 to 259 days.