Effects of Photoperiods on Growth Performance, Serum Biochemical Parameters, Slaughter Performance, Skeletal Development, and Meat Quality of Yellow-Feathered Broilers.

This experiment aimed to investigate the effects of different lighting cycles on the growth performance, serum biochemical indices, slaughter performance, skeletal development, and meat quality of yellow-feathered broiler chickens. A total of 256 10-day-old Liangfenghua yellow-feathered male broilers were randomly assigned to four groups, each with 8 replicates, and each replicate contained 8 chickens. The four lighting cycles used were 18L:6D, 20L:4D, 22L:2D, and 23L:1D (hours of light:dark), and the chickens were fed until 63 days of age. The results indicate that with increasing light exposure duration, the average daily gain and live weight of yellow-feather broilers from 10 to 21 days of age (p = 0.07), the average daily feed intake from 42 to 63 days of age (p < 0.01), as well as the average daily feed intake, daily gain, and feed-to-gain ratio from 1 to 63 days of age (p < 0.05), all showed linear changes. The live weight, daily gain, and feed-to-gain ratio from 42 to 63 days of age exhibited both linear and quadratic variations (p < 0.01). The 22L:2D group achieved the highest live weight and daily gain at 63 days, with the lowest feed-to-gain ratio. Serum glucose levels displayed quadratic variation, while phosphorus levels showed both linear and quadratic changes; the 22L:2D group had the lowest serum glucose and the highest phosphorus levels. The semi-eviscerated rate and the bursa of Fabricius index varied linearly, whereas the leg muscle rate showed quadratic variation. The 20L:4D group had the highest total eviscerated rate, breast muscle rate, and leg muscle rate (p < 0.05), with the lowest Fabricius and thymus indices. The length, width, and volume of the femur and tibia, as well as the tibia bone volume and tissue volume, all changed linearly (p < 0.05). The tibia bone volume fraction exhibited both linear and quadratic changes, with the 18L:6D group showing the highest femur length, width, tibia bone volume, tissue volume, and bone volume fraction. Light exposure significantly affected meat pH, colour, shear force, drip loss, and cooking loss. The crude protein content in the breast muscle showed quadratic variation, while ash and cysteine contents displayed both linear and quadratic changes. The 22L:2D group had the highest crude protein content, pH at 24 h, shear force, and drip loss, but the lowest amino acid and ash contents (p < 0.05). Additionally, there were significant differences in the flavour of the breast muscle under different light cycles. In summary, the photoperiod significantly affects the production performance, skeletal development, meat quality, and flavor of yellow-feathered broilers. The 22L:2D photoperiod yielded the best outcomes in promoting growth, improving feed efficiency, and enhancing meat quality; however, it may adversely affect skeletal development and structural integrity, and caution should be exercised for long-term rearing.