The Effects of Optimal Dietary Vitamin D 3 on Growth and Carcass Performance, Tibia Traits, Meat Quality, and Intestinal Morphology of Chinese Yellow-Feathered Broiler Chickens.

This study aimed to assess the effects of different dietary vitamin D 3 (VD 3 ) levels on growth and carcass performance, tibia traits, meat quality, and intestinal morphology of yellow-feathered broilers. One-day-old broilers (n = 1440) were assigned into four treatment groups with six replicates per group, and each replicate contained 60 chicks. Dietary VD 3 significantly improved the growth performance and carcass traits of broilers, and only low-dose VD 3 supplementation decreased the abdominal fat percentage. High-dose VD 3 supplementation improved intestinal morphology in the finisher stage, while the b* value of breast muscle meat color decreased markedly under VD 3 supplementation ( p < 0.05). Serum Ca and P levels and the tibia composition correlated positively with dietary VD 3 supplementation at the early growth stage. The weight, length, and ash contents of the tibia increased linearly with increasing dietary VD 3 , with maximum values achieved in the high-dose group at all three stages. Intestinal 16S rRNA sequencing and liver transcriptome analysis showed that dietary VD 3 might represent an effective treatment in poultry production by regulating lipid and immune-related metabolism in the gut-liver axis, which promotes the metabolism through the absorption of calcium and phosphorus in the intestine and improves their protective humoral immunity and reduces infection mortality. Dietary VD 3 positively affected the growth-immunity and bone development of broilers during the early stage, suggesting strategies to optimize poultry feeding.