Effects of different stocking densities on growth performance, antioxidant ability, and immunity of finishing...

The study was conducted to evaluate the effects of different stocking densities on growth performance, antioxidant capacity, and immunity of broilers. One thousand four hundred and forty 22-day-old Lingnan Yellow broilers were randomly allotted to five different stocking density groups (8, 10, 12, 14, and 16 birds per m² ). Each group consisted of three replicates. The results showed that 8 and 10 birds/m² groups had higher average daily feed intake (ADFI) than the others (p < 0.05). Heat shock protein 70 (HSP₇₀ ) in the group of 16 birds/m² had the highest levels (p < 0.05). The group of 16 birds/m² had the lowest total antioxidant capability (T-AOC) and total superoxide dismutase (T-SOD) activities in blood serum (p < 0.05), and significantly increased interleukin-1β (IL-1β) and interleukin-4 (IL-4) concentration compared to the groups of 8 and 10 birds/m² (p < 0.05). In liver, the group of eight birds/m² had higher T-AOC levels than that of 12, 14, and 16 birds/m² (p < 0.05) and also higher catalase (CAT) activities than that of 14 and 16 birds/m² (p < 0.05); the group of 10 birds/m² had the highest T-SOD activities among all groups (p < 0.05). In conclusion, the above results suggest that stocking density of broilers up to 8 or 10 birds/m² can prevent the negative effects on growth performance and welfare parameters in broilers.