Abstract：The objective of this study was to review the breast tissue structure and Insulin-like growth factor I receptor (IGF-IR) level of polythelia teats Hu sheep (Ovis aries)(test group), and then detected whether there were some differences between Hu sheep with 2 teats (control group) and polythelia teats and had a potential higher performance of lactation. In this study, the breast tissue samles were taken from 2 groups of Hu sheep during incubation, pregnancy, lactation and nonpregnant period. The changes of mammary gland tissue morphological between 2 groups during different development stages were observed by hematoxylin-eosin staining (HE), the qRT-PCR was used to detect the relative mRNA expression levels of insulin-like growth factor-I receptor gene (IGF-IR). The distribution of receptor protein was detected by immunohistochemistry (IHC). Western blot was used to measure the protein level in mammary gland during different stages. The main findings were showed as follows: During incubationperiod, the mammary stromal was rapidly growthed between the 2 groups, and also contained lots of connective tissue and adipose tissue, in connective tissue, numbers of catheter were denser; during pregnancy period, a large number of gland bubbles were rapidly growed and developed, lobular acini acinus cavity was filled with secretions, and that numbers of gland bubble in test groups were more than that in control groups. The volume of gland bubble was the largest between test and control groups during lactation, and gland bubbles were gradully collapsed and morphological structure of breast was changed after weaning. During lactation, the size and shape of gland bubbles were different, and acinar cavity were reched in milk, the volume of gland bubbles were bigger. The mRNA expression level and protein distribution quantity of IGF-IR intest groupgradually increased from incubation to lactation, however, it was gradually increaseed from incubation to pregnancy and slightly lower than that in pregnancy during lactation period; the expression level in nonpregnant period was lower than those in lactation. And during the entire process of physical development, the proteins of IGF-IR were mainly distributed in mammary epithelial cells and connective tissue between the test and control groups. The protein trend of IGF-IR in breast tissues of Hu sheep was consistent with its mRNA expression level. In summary, not only the breast tissue of Hu sheep with polythelia was more developed, but also the mRNA levels of associated with breast development hormone receptor gene and protein expression levels were higher than those in control groups. It is showed that providing theoretical support for cultivating high-yielding Hu sheep breeds.
