Effects Of Intermittent Low Temperature Stimulation On Growth Performance,Antionxidative Function And Organization Structure Of Broilers

This study was conducted to evaluate the effects of intermittent low temperature stimulation on growth performance, free radicals, antioxidative function, antioxidative gene expression and organization structure of broilers, and to explore the effects of intermittent cold stimulation on resistant capacity of broilers.260healthy Arbor Acres(AA) broilers (Four weeks old) were chosen and randomly divided into12low temperature groups and one control group. Each group was consisted of4replicates and each replicate contained5birds. The results showed as follows:For growth performance, in treatments of1d3℃3h,1d7℃6h,2d3℃6h and2d5℃3h the birds were not affected and no significant difference found compared with the control group(P>0.05). But growth performance of other low-temperature groups were reduced significantly (P<0.05). Daily feed consumption and F/G were improved; daily weight gain was reduced. It showed that different conditioned low temperature stimulation had different effects on the growth performance of broilers.For free radicals, H2O2, NO, NOS, MDA contents in serum were found to be increased of low temperature groups at the fifth week, but serum free radicals in these low temperature groups:1d3℃3h,2d3℃6h, and2d5℃3h were significantly lower than the control group at the sixth week. The results showed that although low temperature had negative effects on serum free radicals, suitable low temperature stimulation plan would reduce the generation of free radicals.For antioxidative status, T-AOC, SOD, GSH-PX, and CAT activities of low temperature groups decreased at the fifth week compared with the control group, but these antioxidative indices for the low temperature groups of1d3℃3h,2d3℃6h, and2d5℃3h were higher than the control group at the sixth week. It showed that in general, although low temperature had negative effects on antioxidative function, better stimulation plan would improve the antioxidative defensive function of broilers.For antioxidative gene expression, mRNA expression of SOD gene and GSH-PX gene in liver and spleen of the broilers in the low temperature groups decreased at the fifth week compared with the control group, but the expression of SOD gene and GSH-PX gene in groups of1d3℃3h,2d3℃6h and2d5℃3h were higher than that of the control group at the sixth week. The influence of low temperature treatments on mRNA expression of SOD gene and GSH-PX gene were consistent with the phenomenon of antioxidative indices SOD and GSH-PX activities. It showed that the influence of low temperature on antioxidative index activities in serum were possibly related to gene transcription regulation.For tissue slice examination, liver structure of1d7℃3h treatment showed pathological changes; liver and spleen structure of1d7℃6h group also showed pathological changes at the fifth week. At the sixth weeks, both liver and spleen structure of1d7℃3h,1d7℃6h and2d7℃6h groups all showed pathological changes. Thus it can be concluded that excessive low temperature stimulation would cause stress and lead to the changes in biological functions, and resulted in pathological tissue structure in liver and spleen at last.It was concluded that growth performance, free radicals, antioxidative status, antioxidative gene expression and tissue structure of broilers were influenced by intermittent low temperature stimulation in many ways. The results of this study indicated that an appropriate low temperature stimulation could have positive effects on broilers in enhancing immunity, such as the conditions of1d3℃3h,2d3℃6h and2d5℃3h.