持续日变高温对猪的铬代谢及血液生化指标的影响

EFFECTS OF LONG TERM HEAT EXPOSURE ON CHROMIUM METABOLISM AND PLASMA BIOCHEMICAL PARAMETERS IN PIGS

本研究选用１６头阉公猪按配对试验设计方法分成适温组（１９℃，５０％ＲＨ）和高温组（２５～３３℃，５０％ＲＨ），研究持续日变高温对猪的铬代谢及血液生化指标的影响，得出：１．随着日变高温的持续，猪血浆铬含量下降（Ｐ＜０．０５）。２．持续日变高温增加猪尿铬的排出量（Ｐ＜０．０５），在高温处理的第７、１４日尿铬排出量比适温组增加４１％和４２％，铬的排出增多意味着机体铬库的不断损耗，则持续日变高温时，猪对铬的需要量增加。３．持续日变高温１４日内，猪血浆皮质醇含量升高（Ｐ＜０．０００１），血浆尿素氮含量升高（Ｐ＜０．００１），血浆总蛋白含量下降（Ｐ＜０．０５）。这表明持续日变高温促进猪机体释放糖皮质激素，从而促进蛋白质分解和糖原异生作用，则机体的糖利用过程加强。４．持续日变高温１４日对猪血浆胰岛素、葡萄糖、甘油三酯、白蛋白和球蛋白含量没有显著影响（Ｐ＞０．０５）。

ixteen crossbred barrow pigs were divided into two groups(thermoneutral vs high temperature)on the basis of ancestry and weight in a paired feeding design.The pigs were individually penned in plasticcoated metabolism crates.The pigs were pairfed twice daily with common diet in 08∶3009∶30 and 16∶3017∶30,and allowed to drink in the rest time.The thermoneutral group maintained at 19℃,50%RH.The high temperature group maintained diurnal condition of 25℃ to 33℃,50%RH.(1)Plasma Cr contents of pigs had declined(P<005)with the lasting of diurnal high temperature.(2)24h urinary excretion of Cr were increased by heat exposure to diurnal high temperature.Compared to pigs of thermoneutral group,24h urinary excretion of Cr in pigs exposed to 2533℃ increased 41% on day 7 and 42% on day 14.These results showed that Cr contents in body stores decreased gradually and Cr requirements for pigs exposed to 2533℃ increased.(3)When pigs exposed to 2533℃ for 14 days,plasma cortisol levels and plasma urea N contents were greater(P<0001)than those at 19℃,but plasma total protein contents were lower(P<005)than those at 19℃. These results showed that long heat exposure for 14 days caused adrenal cortex release of cortisol which enhanced the protein catabolic process,thereby increasing the mobolization of amino acids for gluconeogenesis and the utilization of glucose.(4)Plasma insulin,glucose,triglyceride,albumin and globulin levels were unaffected by long heat exposure for 14 days(P>005).