Impacts Of Biotin On Growth Performance And Immune Function Of Weaned Piglets

Two experiments were conducted to study the effects of biotin on immune response in pigs inoculated intranasally with type-2 porcine circovirus,and cytokine IFN-γand IL-2 mRNA gene expression was examined to discuss the mechanism of biotin affecting Weanling pigs' immune function.Experiment 1:Biotin Supplementation Affects response of immune system of weaned pig of inoculating type-2 porcine circovirus(PCV2)48 Weanling Duroc×Landrace×Yorkshire crossbred pigs initial BW(6.8±0.804) kg with negative PCV2 antibody were used in a 5-wk trial.Exp.1 was conducted to study the effect of supplemental biotin(0,0.05,and 0.20 mg/kg) and PCV2(chanlenged and un-chanlenged) on IL-2,slL-2R,IFN-γconcentrations,and immune response (humoral and cell-mediated).Although the magnitude of the immune response was small and inconsistent,diets containing 0.05 and 0.20 mg/kg biotin seemed to increase the serum immune globulin levels and the percentage of peripheral blood ANAE~+ T cell.IFN-γconcentration was depressed(P＜0.01) aider PCV2 was challenged,especially on 14 and 21 days postinoculation(dpi),and serum IFN-γlevels were increased(P＜0.02 and P＜0.03) for groups fed 0.05 and 0.20 mg/kg supplemental biotin,respectively,and an interaction(P＜0.01) on the 7 dpi was detected,the IFN-γconcentration were highest for PCV2 chanlenged in combination with the 0.20 mg/kg biotin dietary levels.There was no magnificent effect of biotin level on IL-2 and slL-2R concentrations.PCV2 inoculation depressed the immune response and addition of biotin to the diet tended to increase the immune response.Feeding 0.20mg/kg biotin increased growth performance during the 5-wk trials;PCV2 inoculation depressed growth performance after wk 3.The average daily gain of challenged group of supplemental biotin 0.20 mg/kg was higher than that of the un-challenged group whose supplemental biotin was 0.00 mg/kg.Obvious pathological changes(especially in lung,spleen,stomachs and lymph on mesentery) were observed in all challenged pigs.Biotin added in the basal diet at 0.20mg/kg had an ability of relief of pathological lesion of lymphatic organ caused by virus inoculation. Experiment 2:Study of the Appropriate Supplementation Level of Biotin in Corn-Soybean Meal diet for Weaned Piglets Challenged With PCV2The purpose of the Exp 2 was to investigate the appropriate supplementation level of biotin in corn-soybean meal diet for weaned piglets challenged with PCV2.The basal diet was corn-soybean meal diet.There were 6 diets in which boitin was added in the basal diet at 0 mg/kg,0.10 mg/kg,0.20 mg/kg,0.30mg/kg,0.40mg/kg,and 0.50 mg/kg.The results showed as follows:(1) Addition of biotin enhanced significantly T-lymphocyte transformation ratio in blood(P＜0.05),Et-rosette rate and T-lymphocyte transformation ratio of 0.30mg/kg treatment was the greatest on 35 days post-inoculation;(2) The IgG and IFN-γconcentration of 0.30mg/kg treatment were higher significantly on 35 days postinoculation;(3) The growth performance of pigs of 0.50 mg/kg treatment was the best, and the 0.30mg/kg treatment could significantly increased some immuno indexes.(4) With the quantity of supplementation of biotin increasing,the growth indexes of spleen and inguinal lymph nodes of pigs with PCV2 inoculation decreased,on the contrary,the growth indexe of thymus became greater.(5) The treatment of 0.30mg/kg of biotin supplementation level enhanced IL-2 andγ-IFN gene expression,which elevated significantly mRNA expression level of IL-2 andγ-IFN gene(P＜0.01),and there was no significant difference of MCC gene expression in livers of pigs among the biotin addition treatments.In conclusion,the results suggest that PCV2 challenge results in an immune system response,while biotin supplementation increased,the immune response of weanling piglets. Some cytokines' mRNA expression such as FN-γand IL-2 level changing might be the molecular base of biotin on immune function of piglets.