Effect Of Feed Restriction And Compensatory Growth On The Expression Of Somatotropic Axis' Hormones On The Tissues Of Ewes

This study 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, 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. This study focused on the effect of feed restriction and compensatory growth on the expression of somatotropicaxis, hormones on the Ewes. The 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 undernutrition of RG and RG1 ewes was eliminated after parturition.The RT-PCR results are following: At the end of restriction experiment, the GHR mRNA abundance of RG1 was significantly(p<0.01)reduced in liver and was significantly(p<0.01)increased in musculus longissimus dorsi , and the abundance of RG2 was not significant(p>0.05)in liver and musculus longissimus dorsi when compared to CG; The IGF-1 mRNA abundance of RG1 was significantly(p<0.01)reduced in liver and musculus longissimus dorsi and the IGF-1 mRNA abundance of RG2 was not significant(p>0.05)when compared to CG; The GH mRNA abundance of RG1 and RG2 was not significant(p>0.05)when compared to CG . At the end of compensatory growth,the GH, GHR and IGF-1 mRNA abundance of RG1 was not significant(p>0.05)when compared to CG, the abundance of RG2 was also.These indicate that the effect of feed restriction during late pregnancy of ewes on expression of GHR mRNA had tissue specificity: down -regulation in liver and up-regulation in musculus longissimus dorsi, the feed restriction restrained the expression of IGF-1 mRNA in liver and musculus longissimus dorsi, but the level of GHR and IGF-1 mRNA had got back after compensatory growth..The feed restriction and compensatory growth did not affect the expression of GH mRNA.The in situ hybridization result: there were hybridization signals of hepatic cell in each group ewes when cDNA probe of GHR had been used, at the end of restriction experiment, the hybridization signals of RG1 and RG2 were relatively poorer compared to CG, at the end of compensatory growth, the hybridization signals of hepatic cell are not different in each group ewes. The hybridization signals of musculus longissimus dorsi cell are not different in each group ewes; There are poor hybridization signals in hepatic cell and musculus longissimus dorsi cell when oligonucleotide probe of GH had been used, the hybridization signals of each group ewes are not different .