Effects of GABA on the Thymus Cytokines of Wenchang Chickens Submitted to Heat Stress

Under routine feeding conditions, 1-day-old male chicks were randomly divided into control group (CK), heat-stress group (HS), and GABA + heat stress group (GABA+HS). The thymus contents of IL-1, IL-2, TGF-beta 1, IFN-gamma, GH and HSP70 were determined by enzyme-linked immunosorbent assays. The results showed that: (1) IL-1 and TGF-beta 1 contents of HS group were significantly lower than those of the CK group (p<0.05), and those of the GABA+HS group were significantly higher relative to the HS group (p<0.05); (2) IL-2 and IFN-gamma contents of the HS group were significantly higher than those of the CK group (p<0.05), and those of the GABA+HS group were significantly lower relative to the HS group (p<0.05);(3) the thymus GH content of all three groups first increased and then decreased. The expression levels GH of the HS and GABA+HS groups were significantly lower than CK group (p<0.05); and (4) HSP70 expression levels in the thymus were significantly higher in the HS and GABA+HS groups relative to the CK group (p<0.05). These results indicate that heat stress affected thymus development, immune functions, and overall growth of chickens. Furthermore, it was shown that feeding GABA may significantly improve the immune responses of heat-stressed chickens by increasing the expression levels of IL-1 and TGF-beta 1, and effectively alleviate the negative effects of heat stress on thymus development by changing HSP70 expression and GH secretion.