Effect Of Lighting Schedule And Nutrient Density On Growth Performance, Meat Quality And Immune Function In Broilers

The effects of lighting schedule and nutrient density on growth performance, meat quality and immune function of broilers were investigated in a 4×2 experimental design (8 groups of 576 chickens). Four lighting schedules were continuous (23 hr light:1 hr dark, CL),20 L:4 D (12 L:2 D:8 L:2 D),16 L:8 D (12 L:3 D:2 L:3 D:2 L:2 D) and 12 L:12 D (9 L:3 D:1 L:3 D:1 L:3D:1L:3D) respectively. Two nutrient densities were high (H, starter diet:13.39 MJ AME/kg,23.00% CP; finisher diet:13.39 MJ AME/kg,19.70% CP) and low energy and protein level (L, starter diet:12.03 MJ AME/kg,20.8% CP; finisher diet:12.14 MJ AME/kg,18.30% CP). Chickens were randomly allocated to 8 treatments with each treatment 6 replicates of 12 chickens. The experiment lasted 42 days. Feed and water were available ad libitum. The results were as follows:Lighting schedules showed no difference in growth performance at the end the experiment (P>0.05). Breast muscle rate of chickens reared under 12 L:12 D was lower than those under 23 L:1 D and 16 L:8 D schedules (P=0.031). The 12 L:12 D group significantly reduced the concentration of malondialdehyde (MDA) in meat muscle than 23 L 1 D treatment (P=0.048). Intermittent lighting schedules presented higher protein content in breast meat (P<0.001). The 12 L:12 D schedule decreased serum MDA compared with other schedules at 21 d (P<0.001). At 42 d, it was lower in the 12 L:12 D and 16 L:8 D groups than in 23 L:1 D and 20 L:4 D (P<0.001). There was a trend (P=0.086) for greater SOD activity in the 12 L:12 D and 16 L:8 D groups than under the 23 L:1 D and 20 L:4 D schedules at 42 d. A-naphthylacetate esterase (ANAE) positive percentage in 12 L:12 D group at 42 d was higher than in 23 L:1 D and 20 L:4 D groups (P<0.001). Plasma IgG in the 12 L:12 D group at 42 d was higher than in the 23 L:1 D group (P=0.046). HI antibody in the 16 L:8 D group at 21 d was higher than in 23 L:1 D and 12 L:12 D groups (P=0.013).Birds on high density diets had higher BW, FI and FCR throughout the experiment (P<0.001), with an exception in FCR for days 35 to 42 (P>0.05). High nutrient density increased abdominal fat rate (P<0.001), and decreased the moisture loss of meat (P=0.018), wings (P=0.009) and legs percentage (P=0.032). Chickens fed low density diet had a higher fabricius bursa weight (FBW) (P=0.035). Low density diet tended to increase the ANAE positive percentage response at 42 d (P=0.089).There was significant lighting schedule×diet interaction on FCR for days 8 to 14 and 15 to 21 (P<0.001), and also an interaction on FBW at 42 d (P=0.002). Under 23 L:1 D,20 L:4 D and 12 L:12 D treatments, high nutrient density increased FCR, however, failed to increase it under 16 L:8 D treatment. High nutrient density produced heavier FBW in 23 L: 1 D broilers than that in broilers reared under 20 L:4 D schedules. On low density diets, the response to 23 L:1 D schedule was less than in intermittent lighting groups.These results indicated that intermittent lighting schedules improved the meat quality without affecting the growth performance of broilers in comparison with the continuous lighting.12 L:12 D and 16 L:8 D enhanced oxidant-antioxidant balance by decreasing serum MDA and increasing SOD activity, and also enhanced immune functions of broilers by increasing ANAE positive percentage, Plasma IgG and HI antibody. Low nutrient density reduced growth performance and abdominal fat rate and tended to increase the immune functions of broilers.