Effects Of Intermittent Lighting Schedules On The Immune Index And Antioxidant Enzyme Activity In Broilers

Most broiler farms in China have adopted continuous lighting schedule in recent years which have benefit in broiler growth.However, the disadvantage include adding stress and improving the incidence rate of PHS, Leg problem and SDS.Light controlling could prevent these diseases,but the mechanism was still unknown. Furthermore, the study of MEL in broiler has seldom been involved.MEL secretion in mammals are directly affected by illumination and dark will promote secreting ,however light will be the inhibiting factor of secretion. It is reported that MEL of mammals has great function in antioxidation, stress resistance and immunity strengthen.This experiment was designed by evaluating the immunity, anti-oxidant system and free radicals in young broilers under different illumination systems to research that if intermittent light will improve the immunity, anti-oxidant function and disease resistance of young broilers by promoting MEL secretion. We will compare each index of results to choose a better light system for further research and application in production.We randomly selected 1d age of 240 healthy AA broiler birds, divided equally into Control group(C), Light 1 group(L1) , Light 2 group(L2). During the 7-30d, C, L1and L2 group adopted different lighting modes as 24L: 0D, 22L: 2D and 20L: 4D. During the 30-42d, three groups turned to 24 L:0D,with the same feeding.Before every 7 days'feeding,we randomly selected 5 broiler birds and their remaining forage to weigh in each group.During 14d-42d,we randomly selected 10 broiler birds every 7 days to detect the concentration of albumin(ALB),total protein (TP), IgG, IgA, IgM, T-SOD, GSH-PX, MDA and NU-HI in each group.At 14d,28d,35d an42d we randomly selected 5 broiler birds to weigh and dissect in each group, gathering spleen and cloacal bursa to weigh and calculate the index. At 42d we dissect 5 broiler birds in each group to detect the length of intestinal villus.Results:The concentration of TP, ALB and GLB in both of L1 and L2 group were higher than in C; the concentration of IgA in L1 and L2 was higher than in C except 21d and 35d in L1 and 35d in L2; the concentration of IgG in L1 and L2 was higher than in C except 35d in L1; the concentration of IgM in L1 and L2 was higher than in C, and all of these results have not significant difference (P>0.05).Spleen index in L1 and L2 was higher than in C (P>0.05). Cloacal bursa index in L1 was higher than in C except for 14d, and there was no significant difference (P>0.05). cloacal bursa index in L2 was higher than in C except for 28d (P>0.05), however, there was significant difference at 35d(P<0.05).NU-HI was changing irregularity in the experiment.Both of the two intermittent light mode have an effect on the development of young broilers'immune organ by the optical microscope observation : compared with C,in both L1 and L2,the spleen structure of young broilers was distinct ,cells spreaded tight , spleen periarterial lymphatic sheath was obviously increased thickness and lymphocyte was increased; the lymphatic nodule and lymphocyte were both increased in cloacal bursa; the structure of thymus gland was distinct, cells spreaded tight and regulatly. In addition, the villus of duodenum and jejunum in both L1 and L2 were higher than in C (P>0.05).T-SOD was higher than in C except for 35d in L1,moreover there was significant diference at 35d in L2(P<0.05). GSH-PX was higher than in C except for 35d in L2 and MDA was higher than in C except for 35d in L1,however all of these results had no significant diference(P>0.05).From 14d-42d,the body weight in L1 and L2 were lower than in C, moreover there was significant diference at 21d(P<0.05).The rate of feeds and body weight was highest in C and lowest in L2,there was no significant diference among three groups(P>0.05). The morbidity in C, L1 and L2 was 7.5%, 5% and 3.75%.The experiment results indicate that the two intermittent light mode could enhance the immunity and antioxidase activity of young broilers and reduce the incidence of disease, besides, there are not apparently effect on slaughter weigh. Furthermore the effect on TP, ALB, GLB, IgG, spleen index and morbidity in L2 is more obvious than in L1.