| This paper mainly investigated the effect of maternal undernutrition during late pregnancy on the levels of hormones which take the somatotropic axis as the center in ewes and lambs, the expression of partil hormones'mRNA and the gene localization in tissue cells on the basis of animal nutrition, endocrine physiology and by modern molecular biology technique. The experiments explored the mechanism of restriction and compensatory in order to pave the way for applying compensatory growth for animal husbandry scientifically. The results was showed:Part 1 Effect of undernutrition during late pregnancy on the ewes'productivity This study focused on the effect of undernutrition during late pregnancy on the ewes.100 Mongolia ewes, which were synchronized for oestrus and mated at the same day, were selected and divided into three groups offered 0.175 MJME·kgw-0.75·d-1 (Restricted Group1; RG1), 0.33 MJME·kgw-0.75·d-1 (Restricted Group2; RG2) and voluntary intake (Control Group; CG) during their late pregnancy (90 days) respectively. The results indicated that body weights of ewes in RG2 and RG1 were significantly (p<0.01) reduced during feed restricted period. The exogenous energy intake and the intrinsic energy mobilization had negative linear relationship, the less exogenous energy intaked, the more intrinsic energy mobilized; After parturition(during the compensatory period), the growth ratio in RG2 and RG1 was higher than that of CG ,but the difference was not significant(p>0.05).At the end of the compensatory experiment,the body weights of ewes in RG1 was slightly higher and that of ewes in RG2 was slightly lower than that of CG, it was considered that the ewes in RG1 and RG2 showed the phenomenon of complete compensation.The milk yield of ewes in RG2 and RG1 were decreased highly significantly with feed restriction (p<0.01), and the GLU concentration was decreased significantly too(p<0.05). The NEFA and TAA concentration of ewes in RG2 were higher than those of CG (p>0.05) during restriction, but which in RG1 were decreased first then increased and there was no significant difference (p>0.05) compared to CG. the digestibility of DM,CP,NDF and ADF in RG1,RG2 and CG was changed slightly at the different levels of nutrition. Part 2 Effect of undernutrition during late pregnancy on the levels of hormones which take the somatotropic axis as center in ewes and lambs.The results indicated that the GH concentration of ewes in RG2 and RG1 were increased and the difference was significant (p<0.05) at pregnancy d120, and the IGF-1,T3,T4 and INS concentration of ewes were decreased and the difference were not significant (p>0.05) compared to CG with the nutrients supply decreasing during restriction period. The GH, IGF-1 and T3 concentrations of ewes were all decreased first then increased during compensatory period. The GH and IGF-1 concentration of ewes in RG1 and RG2 had significant difference (p<0.05) compared to CG at the beginning of the compensatory (after parturition d30); the T4 concentration of ewes in RG1 and RG2 was increased slowly during compensatory period and lower than that of CG (p<0.05) at the beginning of the compensatory. The INS concentration of ewes was increased during compensatory period. The phenomenon of GH, IGF-1, T3 and INS concentration increased was the one of the mechanisms of complete compensation in RG1 and RG2.The T4, INS, IGF-1,IGF-2 concentration of neonatal lambs were decreased with the nutrients supply decreased and the INS concentration in RG1 was significant lower than CG (p<0.05); the T3 concentration of lambs in RG1 and RG2 were decreased from d75 to the end of the experiment. The INS, GH and IGF-1 concentration of lambs in RG1 and RG2 began to rise at d90 and higher than those of CG. The INS, GH and IGF-I concentration of lambs were increased quickly and the lower energy needed were possibly one of the important mechanisms for lambs showing compensatory growth at 90 daysPart3 Effect of undernutrition during late pregnancy on expression of GH, GHR and IGF-1, IGF-1R mRNA on the ewes and lambsThe effect of undernutrition during late pregnancy on expression of GHR mRNA on the ewes had tissue specificity: down -regulation in liver and up-regulation in musculus longissimus dorsi. At the end of restriction experiment, the abundance of GHR mRNA in liver of ewes in RG1 was significantly (p<0.01)reduced when compared to CG and in musculus longissimus dorsi was significantly (p<0.01)increased. and the abundance of GHR mRNA in liver and musculus longissimus dorsi of ewes in RG2 was not significant (p>0.05)when compared to CG. At the end of experiment,the abundance of GHR mRNA in liver and musculus longissimus dorsi of ewes in RG2 and RG1was decreased the level of CG ; The undernutrition during late pregnancy restrained the expression of the abundance of IGF-1 mRNA in liver and musculus longissimus dorsi of ewes in RG1 was significantly (p<0.01)reduced when compared to CG. The abundance of IGF-1 mRNA in liver and musculus longissimus dorsi of ewes in RG2 was changed not significantly(p>0.05). At the end of experiment,the abundances of IGF-1 mRNA in liver and musculus longissimus dorsi of ewes in RG2 and RG1 was increased to the level of CG .The undernutrition during late pregnancy restrained the expression of GHR and IGF-1 mRNA in liver and musculus longissimus dorsi of lambs. The abundance of GHR and IGF-1 mRNA of nascent lambs in RG2 and RG1 was significantly (p<0.01)reduced when compared to CG. The abundance of GHR and IGF-1 mRNA in RG2 was changed not significantly (p>0.05)compared with CG, however, that in RG1 was highly lower (p<0.05)than RG1 at 28 weeks.The maternal undernutrition during late pregnancy did not effected on the expression of GH and IGF-1R mRNA in liver and musculus longissimus dorsi of ewes and lambs .The abundance of GH and IGF-1R mRNA in RG2,RG1and CG were not significantly (p>0.05)from begin to end of experiment.Part4 The localization of the expression of GH and GHR mRNA in liver and muscle on ewesThis research was carried out in situ hybridization by DIG-labeled DNA probes.The results indicated that the expression of GH mRNA was in intracytoplasm of hepatocellular but not in hepatic, the expression of GHR mRNA was in cellular membrane of hepatocellular. The expression of GH and GHR mRNA were in muscular fibril of musculus longissimus dorsi. |
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