瘤胃乙酸、丙酸比例对绵羊体内氧化代谢和血浆胰岛素水平动态变化的影响

本研究以全胃营养灌注绵羊为试验动物 ,用物质代谢区室分析方法和同位素示踪技术研究了瘤胃乙酸、丙酸比例对体内氧化代谢和血浆胰岛素水平动态变化的影响。不同试验处理间营养灌注液能量、蛋白质水平相同 ,而瘤胃灌注混合挥发性脂肪酸的乙酸、丙酸比例不同。三种混合挥发性脂肪酸的乙酸、丙酸比例分别为75 :15(VFA1)、65 :25(VFA2)、45 :45(VFA3)。由测定引入 14C -乙酸后血液二氧化碳放射比强度—时间曲线上升段斜率(k值)反映体内氧化代谢强度。试验结果为 ,瘤胃灌注VFA1 时的k值显著高于灌注VFA2 和VFA3 时的k值(P<0.05) ,而VFA2 和VFA3 两处理间的差异不显著(P>0.05) ,说明瘤胃灌注VFA1 时绵羊体内氧化代谢强度增加。向停止灌注24小时的绵羊瘤胃内灌注VFA1,血浆胰岛素水平在恢复灌注后缓慢上升。将瘤胃灌注混合挥发性脂肪酸由VFA1 换为VFA2 后 ,血浆胰岛素水平迅速上升 ,之后迅速下降 ,而由VFA2 换为VFA3 后未出现血浆胰岛素水平的明显变化 ,说明血浆胰岛素水平的变化与体内糖代谢调节状态有关 ,而瘤胃灌注VFA1 时的体内糖代谢调节状态与灌注VFA2 和VFA3 时明显不同。

EFFECT OF RATIO OF ACETATE TO PROPIONATEIN THE RUMEN ON THE INTERMEDIATE OXIDATIVEMETABOLISM AND PLASMA INSULIN LEVEL OF SHEEP

The experimental sheep were maintained by intragastric nutrition with an energy level of 1.3 maintaince and a protein level of 1.5 maintaince.The ratios of acetate to propionate of the three volatile fatty acid mixtures are 75:15(VFA1),65:25(VFA2),and 45:45(VFA3) respectively.14C-acetate was infused into the jangular vein or portal vein catheter and blood samples were drained from the jangular artery or jangular vein catheter at different time after the beginning of tracer infusion.A three compartment model were used to analyze the measurements of specific activity of carbon dioxide in blood samples and the slope of the specific activity-time curve were used to describe the intensity of intermediate metabolism with the higher the slope the more intensive the oxidative metabolism.The results indicated that the slopes obtained when VFA1 were infused are higher than those obtained when VFA2 or VFA3 were infused into the rumen of the two sheep(P<0.05),which implies that when VFA1 were infused there were more organic mater were oxidized during intermediate metabolism.One of the tested sheep were stopped for nutrient infusion for 24 hours and then reinfused with VFA1 and other nutrients.Blood samples were drained from jangular vein catheter at different time points after reinfusion for the analysis of plasma insulin level.On the second day of reinfusion,the volatile fatty acid mixture infused into the rumen were changed to VFA2 and on the third day changed to VFA3.After reinfusion,plasma insulin level increased in a slow rate,and after the volatile fatty acid mixture changed to VFA2,there was a sharp increase of insulin level and followed with a sharp decrease.When the volatile fatty acid mixture changed to VFA3,there nas no signficant change of insulin level.The results imply that the state of glucose metabolism may be different from other volatile fatty acid mixtures when VFA1 were infused.