Effect Of 25-oh-d₃ On Growth Performance, Intestinal Immune Function And Immune Stress In Weanling Pigs

Two experiments were conducted to investigate the effects of dietary 25-OH-D3 on the intestinal immune function, growth performance, immune stress response, and the suitable dietary 25-OH-D3 level in weanling pigsExperiment 1:Effect of dietary 25-OH-D3 on the intestinal immune function and growth performance in weanling pigs challenged by rotavirusThe experiment was arranged in a 2×2 factorial design with the main effects of rotavirus challenge and dietary 25-OH-D3. In a 28-d experiment,48 (Duroc×Landrace×Yorkshire) pigs (initial BW 7.35kg and 28d age) were used. Each treatment was replicated with 12 pigs. The pigs of control groups (C-,C+) and treatments (T-, T+) were fed diets with dietary 25-OH-D3 level 220 or 2200IU/kg respectively. The treatment C+ and T+ were challenged orally with 1×106TCID human rotavirus, while the treatment C- and T- were inoculated orally with MEM liquid. The pig growth performance, antibody and cytokines in serum and intestinal contents, the percentage of T cell subsets from ileum intraepithelial lymphocytes(IEL), lamina propria lymphocytes(LPL), and mesenteric lymph node(MLN) were determined. The results indicated that the addition of 2200IU/kg 25-OH-D3 in weanling pigs:①decreased the ratio and index of diarrhea from d 4 to 14.②enhanced the ADG, ADFI, and G/F of unchallenged and challenged rotavirus pigs from d 0 to 15.③had no remarkable effect on villus height and crypt depth of ileum.④elevated the level of rotavirus antibody in serum and intestinal contents of challenged pigs at d 5,15 and 21;had enhanced the level of IgG, IgM and IgA in intestinal contents intestinal contents of unchallenged and challenged pigs; had depressed the level of IgG, IgM and IgA in serum of unchallenged and challenged pigs at d 5,15 and 21.⑤enhanced the percentage of CD3+,CD4+at d 5,15 and 21, decreased the percentage of CD8+T cell in ileum IEL and LPL at d 5 and 15, increased the ratio of CD4+/CD8+T cell at d 5,15 and 21; had no significantly effect on T cell subsets in ileum MLN.⑥reduced the level of IL-2 in serum and intestinal contents of unchallenged pigs at d 15 and 21, decreased the level of IL-2 in intestinal contents of challenged pigs at d 5,15 and 21; elevated the level of IL-4 in serum and intestinal contents of unchallenged and challenged pigs at d 5,15 and 21; depressed the level of IL-6 in serum and intestinal contents of unchallenged pigs at d 5 and 15, reduced the level of IL-6 in intestinal contents of challenged pigs at d 5,15 and 21; decreased the level of IFN-y in intestinal contents of unchallenged and challenged pigs at d 5,15 and 21, had no significantly effect on the level of IFN-y in serum of pigs.Experiment 2:Effect of graded dietary vitamin D3 on growth performance and immune stress response induced by lipopolysaccharide in weanling pigsThe experiment was conducted to investigate the effect of graded dietary 25-OH-D3 on pig growth performance from d 0 to 21.112 crossbred (Duroc×Landrace×Yorkshire) pigs (initial BW 6.73kg and 21d age) were used. Pigs were randomly allotted to 1 of 7 treatments with 25-OH-D3 supplemented at 0,440, 880,1320,1760,2200IU/kg or 2200 IU/kg D3. Each treatment was 4 replicates (pens) with 4 pigs per pen. After the 21-d experiment, an experiment was conducted to determine the effect of dietary 25-OH-D3 on the immune stress responses induced by LPS in pigs from d 21 to 28. On d 21, two pens pigs from each treatment groups was challenged with E. coli LPS (100μg/kg of BW) or injected with sterile saline (±LPS challenge;±graded dietary 25(OH)D3; n=8 pigs/treatment group). The pig growth performance, Immunoglobulin, cytokines IL-6, TNF-a and IGF-Ⅰin serum were determined. The results indicated, The dietary supplemented:①25-OH-D3 of 2200IU/kg had enhanced the ADG, ADFI of weanling pigs from d 0 to 21; 25-OH-D3 of 880 to 2200 IU/kg and D3 of 2200 IU/kg had elevated strongly the ADG, ADFI and G/F of LPS stressed pigs from d 21 to 28.②25-OH-D3 of 1320 to 2200 IU/kg had depressed the levels of IgG, and more significantly decreased the level of IgA in serum of LPS stressed pigs at d 28.③25-OH-D3 of 880 to 2200 IU/kg and of D32200 IU/kg had decreased the level of IL-6 in serum of LPS stressed pigs; 25-OH-D3 of 1320 to 2200 IU/kg had deduced the level of TNF-a in serum of LPS stressed pigs.④25-OH-D3 of 880 to 2200 IU/kg and of D32200 IU/kg had forcefully elevated the level of IGF-Ⅰin serum of LPS stressed pigs. the levels of 25-OH-D3 was positive relation with level of IGF-Ⅰof pigs.In CONCLUSION:25-OH-D3 can enhance differentiation, maturation of T cell in ileum mucous of weanling pigs, promote the response that is concerned with T helper cell, inhibit the function of T killed cell, depress the inflammation response participated with Th1 type helper cell, facilitate the anti-inflammation response involved with Th2 type helper cell, elevate the intestinal immune function. The dietary 25-OH-D3 supplementation can decrease the secretion of proinflammatory cytokines IL-6 and TNF-a of immune stressed pigs, strengthen the production of IGF-I, decrease the negative effect of immune stress on pigs and enhance the pig growth performance. The dietary supplemental 2200IU/kg 25-OH-D3 can increase the pig performance at the normal condition,880 to 220025-OH-D3 can elevate the pig growth performance at the stress condition.