阿勒泰羊生长速度与主要血液生化指标含量及尾脂Leptin基因表达关系

试验通过研究不同生长速度阿勒泰羊主要血液生化指标含量和尾脂中瘦素（Leptin）基因的表达水平，探讨阿勒泰羊生长速度与脂肪沉积之间的关系。选取300只出生时间相近的阿勒泰羊公羔，正常饲喂至6月龄，记录日增重，取平均日增重排前10%和后10%的公羔各30只，分为生长快速组（HBW）和生长慢速组（LBW），从生长快速组随机选12只分为抑制生长组（饲喂低能量饲粮以抑制其生长，HBW-75%，n=6）和生长快速对照组（饲喂标准饲粮，HBW-100%，n=6），生长慢速组随机选12只分为促进生长组（饲喂高能量饲粮以促进生长，LBW-125%，n=6）和生长慢速对照组（饲喂标准饲粮，LBW-100%，n=6）；预饲期7 d，正饲期30 d，试验结束后称重并采集血液，屠宰后采集尾部脂肪。检测血液TG、CK、TSH、T3、T4、S.S、GH、INS、PG、Leptin含量或活性及尾部脂肪Leptin mRNA和蛋白表达量，并观察尾部脂肪细胞形态学变化。结果显示，HBW-100%和LBW-100%组初体重与末体重均差异显著（P<0.05），HBW-75%和HBW-100%组初体重与末体重均无显著差异（P>0.05）；LBW-100%和LBW-125%组初体重差异显著（P<0.05），末体重无显著差异（P>0.05）。LBW-100%组的T4、S.S、Leptin、TSH、T3含量显著低于HBW-100%组（P<0.05）；LBW-125%组T3含量显著高于LBW-100%组（P<0.05）；HBW-75%组GH、PG和Leptin含量显著低于HBW-100%组（P<0.05）。LBW-125%组尾部脂肪细胞面积大于LBW-100%组，HBW-75%组小于HBW-100%组（P<0.05）。Leptin mRNA和蛋白表达量检测结果表明，HBW-100%组的Leptin mRNA表达量与LBW-100%组无显著差异（P>0.05），Leptin蛋白表达量极显著高于LBW-100%组（P<0.01）。LBW-125%组Leptin mRNA和蛋白的表达量均显著高于LBW-100%组（P<0.05）。HBW-75%组Leptin mRNA的表达量极显著低于HBW-100%组（P<0.01），Leptin蛋白表达量显著低于HBW-100%组（P<0.05）。综上所述，生长快速组与生长慢速组中，Leptin的表达量与体重和体脂有一定关联；在生长慢速组促进生长后体重和体脂显著增加，Leptin的表达量呈上升趋势；在生长快速组抑制生长后体重和体脂减少，Leptin的表达呈下降趋势。改变生长速度对Leptin的表达量会产生影响，从而改变机体的脂肪沉积状况。

The Relationship Between the Growth Rate of Altay Sheep and the Content of Main Blood Biochemical Indexes and the Expression of Leptin Gene in Tail Fat

The purpose of the experiment was to investigate the relationship between the growth rate of Altay sheep and the fat deposition by studying the content of main blood biochemical indicators and the expression level of the Leptin gene in the tail fat of Altay sheep at different growth rates.300 Altay rams with similar birth times were selected and fed normally to 6 months of age.During this process,the daily weight gain was recorded.Then the sheep whose daily weight gain was top 10% was defined as the fast growth group (the group with higher body weight,HBW),and those whose daily weight gain was bottom 10% was devided into the slow growth group (the group with lower body weight,LBW).From the fast-growing group,12 sheep were randomly selected and divided into growth inhibition group (low-energy diets,HBW-75%,n=6) and control group (standard diet,HBW-100%,n=6).In the slow growth group,12 sheep were randomly selected into the growth promotion group (high-energy diets,LBW-125%,n=6) and the control group (standard diet,LBW-100%,n=6).After 7 d of prefeeding,the sheep were fed for another 30 d,at the end of feeding,the sheep were weighted and the blood were collected,and tail fat was collected after slaughter.The levels of TG,CK,TSH,T3,T4,S.S,GH,INS,PG,Leptin in blood,the expression of Leptin mRNA and protein,and the morphological changes of tail fat cells were measured.The weight results showed that the initial weight and final weight of the HBW-100% and LBW-100% groups were significantly different (P<0.05),HBW-75% and HBW-100% groups had no significant difference in initial body weight and final body weight (P>0.05);LBW-100% and LBW-125% groups had significant difference in initial body weight (P<0.05),but no significant difference in final body weight (P>0.05).The T4,S.S,Leptin,TSH and T3 content in the LBW-100% group were significantly lower than those in the HBW-100% group (P<0.05).The T3 content in the LBW-125% group was significantly higher than that in the LBW-100% group (P<0.05).The content of GH,PG and Leptin in the HBW-75% group were significantly lower than that in the HBW-100% group (P<0.05).The tail fat cells in the LBW-125% group were larger than that in the LBW-100% group,and the HBW-75% group was smaller than the HBW-100% group (P<0.05).The detection results of Leptin mRNA and protein expression levels showed that there was no significant difference between the Leptin mRNA expression levels in the HBW-100% group and the LBW-100% group (P>0.05),and the Leptin protein expression levels were significantly higher than that in the LBW-100% group (P<0.01).The expression of Leptin mRNA and protein in the LBW-125% group were significantly higher than that in the LBW-100% group (P<0.05).The expression of Leptin mRNA in the HBW-75% group was significantly lower than that in the HBW-100% group (P<0.01),and the expression of Leptin protein was significantly lower than that in the HBW-100% group (P<0.05).In summary,in the fast-growing group and the slow-growing group,the expression of Leptin had a certain connection with body weight and body fat.In the slow-growing group,body weight and fat were increased significantly after promoting growth,and the expression of Leptin showed an upward trend.In the fast-growing group,after inhibiting growth,the body weight and fat were decreased,and the expression of Leptin showed a downward trend.The change of growth rate would affect the expression of Leptin,thereby changing the fat deposition.