Effects of light regime on the hatching performance, body development and serum biochemical indexes in Beijing You Chicken

The paper aimed to study the effects of light regime during the incubation on hatching performance, body development and serum biochemical indexes in Beijing You Chicken (BYC). A total of 1,408 BYC eggs were randomly allocated into 4 groups: 24 h dark as the control (Inc_24D); 3 light regimes were 8 h light and 16 h dark group (Inc_8L:16D); 12 h light and 12 h dark group (Inc_12L:12D); 16 h light and 8 h dark group (Inc_16L:8D), respectively. There were 352 eggs in each group, 4 replicates each group and 1 tray each replicate, 88 eggs each tray. Light-emitting diode (LED) strips, white light with temperature of 4,500 to 5,000 K, 150 to 200 lx were set up. The results showed that light regimes had no significant effects on hatching rate of eggs, hatching rate of fertile eggs and healthy rate of chicks (P > 0.05), but the hatching rate of eggs was the lowest in the Inc_24D group (87.22%), and the highest in the Inc12L:12D group (93.64%); Lighted incubation significantly affected the incidence of leg problems of 1-day-old chicks (P < 0.05). The incidence rate of leg problems was the highest in the Inc_24D group (4.21%), and was decreased in Inc_12L:12D and Inc_16L:8D groups (P < 0.05). Femur length in the Inc_12L:12D group was greater than that in the Inc_24D and Inc_16L:8D groups (P = 0.011), but there were no differences between Inc_8L:16D group and other three groups (P > 0.05). The relative brain weight of 1-day-old chicks was higher in Inc_24D and Inc_16L:8D groups than in Inc_8L:16D group (P = 0.052), but had no difference with Inc_12L:12D group. Light regimes during incubation had no effects on serum total protein, albumen, globulin, and urea nitrogen content of 1-day-old chicks (P > 0.05), while the globulin content in Inc_12L:12D group was numerically greater than in other three groups (P = 0.063). Lysozyme content in Inc_12L:12D group was higher than that in the Inc_24D and Inc_8L:16D groups (P < 0.05), but had no difference with that in Inc_16L:8D group. Light regime had no effect on serum total antioxidant capability (T-AOC) (P > 0.05), but significantly affected the activities of glutathione peroxidase (GSH-Px) and total superoxide dismutase (T-SOD) (P < 0.05). The GSH-Px and T-SOD activities in the Inc_12L:12D group were higher than those in the Inc_24D and Inc_8L:16D groups. The MDA content of Inc_24D was the highest (9.67 nmol/mL) compared to the others, which was very close to the significant level (P = 0.056). In conclusion, 12 h light and 12 h dark incubation has the potential to improve the hatching performance of BYC eggs, benefit for the long bone development, improve some serum immune and antioxidant indexes, and reduce the leg problems in 1-day-old chicks.