Effects Of Added VD₃ In The Diet On Growth Performance And Immune Function In Sichuan Black-bone Chickens

Traditionally, the physiological function of vitamin D₃ and its derivatives was confined to regulate the calcium and phosphorus balance of body. However, as the deepening of investigation, it was found that VD₃ also play an important role in immunoregulate, as it can regulate the differentiation, proliferation of a variety of cells,and can regulate the immune function of animal.However, the current understanding mentioned above is mainly from in vitro investigations. As the studies of vitamin D₃ are rarely conducted in vivo, the findings of immunomodulatory function are not consistent. Based on previous studies, this study was conducted to investigate the effect of different dosages of VD₃ supplement on growth performance, microbial population of appendix, intestinal tissue structure and immune function of Sichuan bone-black chickens at different stage, in order to explore the mechanism on immune function and a reasonable supplement does of VD3. This study also provide a numerical data for nutrition regulation of immunity to promote the healthy growth of Sichuan black-bone chicken.This study was conducted with simple factor experiment arrangement. One hundred and twenty 8-day-old Sichuan black-bone chickens with similar body weight were selected and randomly divided into four groups, which were replicated three times with ten chickens.The control group was fed with basal diet, while the treatment groups were fed with basal diet supplemented with 800IU/kg,1600IU/kg,3200IU/kg VD₃ respectively. We measured that of growth performance, microbial population of appendix, villus length and ratio of villus length and crypt-depth, index mumber of immune organ, phagocytic function index of mononuclear-macrophage, the level of antalzyme, immunoglobulin and C3, C4 in serum, serum-albumin and total serum protein of 35-day-chickens and 63-day-chickens.Results were summarized as follows.(1) Compared with the control groups, the growth performance of Sichuan black-bone chickens fed withVitamin D₃(800IU/kg,1600IU/kg) was increased significantly.According to the comprehensive analysis of performance, supplementation of VD₃ at 800IU/kg in diet showed the best effect, and the performance in 8³5 days was better than in 36⁶3 days.(2) Supplementation of 1600IU/kg VD₃ significantly decreased the amount of colibacillus population ofappendix of the 35-day-chickens and 63-day-chickens, and significantly improved the amount of lactobacilli population of appendix of 35-day-chickens.(3) Enzyme activity of duodenum-amylase were not effected by the VD₃ supplemention at 35-day-old(P＞0.05). However, when the supplemention of the VD₃ raised to 3200IU/kg, the enzyme activity of entero-amylase chyme ot'63-day-chickens was decreased significantly(P＜0.05).(4) Compared with the control group, it was found that 1600IU/kg VD₃ could significantly improve thelength of intestinal villi of the 35-day-chickens and 63-day-chickens (P＜0.05), the ratio of villus length and crypt-depth of the 35-day-chickens (P＜0.05),and especially the ratio of villus length and crypt-depth of 63-day- chickens (P＜0.01).(5) It was found that 1600IU/kg VD₃ could significantly improve the phagocytic function of mononuclear-macrophagus of Sichuan black-bone chickens at 35-day-old and 63-day-old (P＜0.05, P＜0.01),and supplementation of 3200IU/kg VD₃ significantly improved the phagocytic function of mononuclear-macrophagus of 63-day-chickens.(6) Supplementation of 1600IU/kg VD₃ extreme significantly improved the amount of antalzyme inserum of Sichuan black-bone chicken at 35 and 63 days(P＜0.01),while antalzyme of 35-day-chickens increased significantly with 32001U/kg supplied(P＜0.05).(7) Vitamin D₃ (1600IU/kg)could significantly improve the level of serum-albumin of sichuan black-bone chicken at 35-day-old and 63-day-old(P＜0.05). Vitamin D₃ (800IU/kg) improved the level of serum-albumin at the day of 63 significantly (P＜0.05).(8) The results indicated that the level of total serum protein of Sichuan black-bone chicken with VD₃additives were increased significantly at the day of 35 and 63, especially with 1600IU/kg VD₃(P＜0.01,(P＜0.05).(9) It was found that VD₃ of 800IU/kg,1600IU/kg improved the level of immunoglobulin IgM,IgG inserum significantly(P＜0.05or P＜0.01,), and had no effect on the level of IgA in serum, when the amount of VD₃ raised to 3200IU/kg, the level of IgM, IgA in serum showed a trend to decrease.(10) Diet added with different levels of VD₃ can increase the level of serum complement C3 at the day of 35 and 63, and the level of serum complement C4 at the day of 35 in a dose-dependent, when VD₃ increased to 3200IU/kg, the level of C3 and C4 were increased significantly compared with the control group(P＜0.05).Based on the results of growth performance, length of intestinal villi, microbial population of appendix and immune function, We concluded that the fittest addition dose of VD₃ for feeding the Sichuan black-bone chickens is 1600IU/kg. Moreover, the effect of supplement in the early stage (8 35 days) would be better than the later period(36⁶3 days).