Effects Of Moderate Thermal Temperatures On Physiological And Biochemical Indices And AvUCP MRNA Expression Related To Thermal Regulation Of Broilers

Poultry was homothermous animal. High ambient temperature influenced its thermal balance, meanwhile had an effect on the performance and health. Heat stress in summer was one of the important problems on the poultry cultivation in our country. Previous studies heat stress focused on above 32℃, while the effect of moderate thermal temperature(below 32℃) on broilers was rarely reported. As the improvements of cooling technique for hen house in summer, the effect of long-term heat stress above 32℃ on broilers was decreased and people pay more attention to delicacy management with the development of modern scale raise. Therefore, study on physiological and biochemical indices related to thermal regulation of broilers under moderate thermal temperature may help us evaluating thermal comfort, improving thermal environment and increasing economic efficiency of broilers.In this research, 26 ℃ and 31 ℃ these two difference moderate thermal temperatures were detected, while the 21℃ was as control. After acute(2 hours) and constant(7 and 14 days) exposure, the performance of broilers, viscera indices, serum electrolyte, blood gas, physiological and biochemical indices were recorded and tested. The av UCP m RNA expression in the pectoral muscle and liver tissue was analyzed. The main results of this research were showed as follows:1. After two hours exposure in 26℃, the rectal and skin temperatures were higher, but Na+ and T3 of broilers were lower than in 21℃. There was no difference in respiratory frequency and blood gas. After two hours exposure in 31 ℃, the physiological indices(rectal and skin temperatures, and respiratory frequency) were increased compared to in 21℃. Blood gas(p H, PO2, PCO2 and HCO3-) and biochemical indices were also changed.2. The result of constant 26℃ exposure-showed depression of average daily gain(ADG), average daily feed intake(ADFI) and heart index were decreased, but there was no effect on feed conversion ratio(F/G). The ADG, ADFI, F/G, heart and kidney index had a depression when the broiler was exposure in 31℃.3. There was no effect on average daily water consumption(ADWC) after the broiler exposure in 26℃ and 31C℃, but the water/feed(W/F) and water/gain(W/G) were raised. The W/F had significant negative correlations with the performance of broilers, and positive correlations with the ambient temperatures and physiological indices. Constant 26℃ exposure showed depression of Na+. Constant 31℃ exposure showed increase of respiratory frequency and PO2, with depression of Na+ and ADH.4. Constant 26 ℃ and 31 ℃ exposure showed increase of rectal and skin temperatures. The skin temperature of ear had positive correlations with ambient temperatures and rectal temperature of broilers. Constant 26 ℃ exposure showed increase the concentration of T4, while the avian uncoupling protein(av UCP) m RNA expression in pectoral muscle was decreased. Constant 31℃ exposure showed increase in serum glucose and lipid, with significant difference of endocrine indices(T4, CORT and LEP). The av UCP m RNA expression in pectoral muscle was decreased but the expression level in liver was increased.The results showed that:(1) According to the effects of 26℃ and 31℃ on physiological and biochemical indices, gene expression and the performance of broilers, the 26℃ and 31℃ ambient temperatures were belong to moderate thermal temperature for broilers.(2) Compared to 21℃, 26℃ exposure showed significant depression of performance of broilers, and mainly showed difference of heart index, rectal and skin temperature, T3 and T4, Na+ and av UCP m RNA expression in pectoral muscle, with no difference of the others recorded.(3) In addition to which index changed in 26℃, 31℃ exposure also had influence on av UCP m RNA expression in the liver and multiple physiological and biochemical indices, like respiratory frequency, K+ and GLU.(4) The W/F could be used as a non-invasive index for thermal comfort evaluation of broilers.(5) The skin temperature of ear which as a non-invasive index, could be used for thermal comfort evaluation of broilers as same as the rectal temperature.