【摘要】 本文旨在研究饲粮能氮限饲与补偿对蒙古羔羊肝脏重量、肝细胞增殖和增肥及生长激素受体(GHR)、类胰岛素生长因子Ⅰ(IGF-Ⅰ)、类胰岛素生长因子Ⅱ(IGF-Ⅱ)基因表达量的影响。选用体重相近的蒙古羔羊80只,随机分为4组,分别为对照组、蛋白质限饲组(PR组)、能量限饲组(ER组)、蛋白质能量双重限饲组(BR组),限饲期(60 d)内各组分别饲喂粗蛋白质(CP)为15.08%、9.24%、15.01%和6.27%,对应代谢能(ME)为10.61、10.49、8.36和8.10 M J/kg的饲粮。之后的90 d补偿期,各组均饲喂相同营养水平(CP为12.48%、M E为9.77 M J/kg)的饲粮。分别于限饲期和补偿期结束时屠宰,采集肝脏组织,称重,测定肝脏DNA含量、肝细胞DNA和蛋白质浓度,并应用实时定量PCR技术检测GHR、IGF-Ⅰ和IGF-Ⅱ基因表达量的变化。结果表明:限饲60 d后,ER组(P<0.05)、BR组(P<0.01)羔羊肝脏重量显著或极显著低于对照组;PR组、ER组和BR组肝细胞数量均低于对照组,肝细胞体积变化不大;各限饲组羔羊肝脏IGF-Ⅰ基因表达量显著低于对照组(P<0.05);PR组(P<0.01)、ER组(P<0.01)和BR组(P<0.05)羔羊肝脏IG F-Ⅱ基因表达量显著或极显著低于对照组。补偿90 d后,各限饲组羔羊肝脏重量、肝细胞数量、肝细胞体积以及GHR、IGF-Ⅰ和IGF-Ⅱ基因表达量与对照组均无显著差异(P>0.05)。结果提示,3月龄开始限饲的蒙古羔羊,限饲能量对肝脏生长发育的抑制强于比限饲蛋白质,而蛋白质能量双重限饲造成的负面影响最大;单独限饲能量或蛋白质羔羊肝脏中GHR、IGF-Ⅰ和IGF-Ⅱ基因表达量的下降幅度大于蛋白质能量双重限饲;经过饲粮能氮补偿,限饲影响的指标均恢复到与未限饲相同水平。更多还原

【Abstract】 This study was conducted to investigate the effects of dietary restriction and realimentation on energy and nitrogen on liver weight,proliferation and expansion of liver cells and expression levels of growth hormone receptor(GHR),insulin-like growth factor Ⅰ(IGF-Ⅰ) and insulin-like growth factor Ⅱ(IGF-Ⅱ) genes in liver of Mongolian lambs.Eighty lambs with similar body weight were divided into 4 groups: control group,protein-restricted group(PR),energy-restricted group(ER),and protein and energy-restricted group(BR).Lambs in the 4 groups were fed the diets with following nutrient levels during 60 days of restriction period: crude protein(CP was 15.08%,9.24%,15.01% and 6.27%,respectively,and accordingly,metabolizable energy(ME) was 10.61,10.49,8.36 and 8.10 MJ/kg,respectively.Then,lambs in the 4 groups were fed the same diet(CP) was 12.48% ME was 9.77 MJ/kg) during 90 days of realimentation period.At the end of restriction and realimentation periods,lambs were slaughtered to collect liver tissue for the analysis of liver weight,liver DNA content,and DNA and protein concentrations in liver cells.RT-qPCR were used to detect the expression levels of GHR,IGF-Ⅰ and IGF-Ⅱ genes.The results showed as follows: after 60 days of restriction period,liver weight of lambs in ER(P<0.05) and BR groups(P<0.01) was significantly lower than that in control group;liver cell counts of lambs in PR,ER and BR groups were lower than those in control group,no obvious expansion was found;IGF-Ⅰ gene expression level in PR,ER and BR groups was significantly lower than that in control group(P<0.05).After 90 days of realimentation period,no significant differences were found in liver weight,liver cell counts,liver cell size and the expression levels of GHR,IGF-Ⅰ and IGF-Ⅱ genes among all groups(P>0.05).The results indicate that after adapting restriction on lambs at 3 months of age,the inhibition effects of energy restriction on liver growth are larger than those of protein restriction,and those of restriction on protein and energy are the largest;down-regulation on the expression levels GHR,IGF-Ⅰ and IGF-Ⅱ genes of protein or energy restriction adapted alone was much more than that of restriction both on protein and energy;after dietary realimentaion,the indices of restricted lambs can be restored to the same level as that of unrestricted lambs.更多还原