小尾寒羊母性行为投入差异及其调控机制研究

The Small-Tail Han sheep is a famous prolific sheep breed in our country and even all over the word. This sheep breed has many excellent characteristics such as precocity, non-seasonal estrus, multiple litters and so on. Currently, the higher mortality rate of lambs before weaning restricts the development of Small-Tail Han sheep industry which is one of the most difficult problems to be solved. Good maternal behaviour input is a key to improve survival rate of multiparous lambs. However, the differences of maternal behaviour input and its endocrine, molecular mechanism in Small-Tail Han sheep to multiple lambs are still unknown. Therefore, this research project will take primiparous and multiparous ewes with twin or triplet lambs as research objects and will clarify the relationships between the input differences of maternal behaviour and lambs growth by maternal behavior observation. Then, the hormones that are related to maternal behavior input will be expounded by detection of the estradiol, oxytocin and cortisol levels in ewe plasma. Thirdly, this project reveals that the relationship between mRNA expression and DNA methylation of hormone receptors. Synthesizing all the results from aforementioned behaviour, endocrine, and molecular levels, this project reveals the differences of maternal behaviour input and its regulation mechanism in Small-Tail Han sheep. This research will provide theoretical basis for improving the animal behavioral traits and lamb survival rate.

小尾寒羊具有性成熟早、常年发情、一胎多羔等优良性状，是我国乃至世界著名的高产绵羊品种。目前，断奶前羔羊的较高死亡率是小尾寒羊规模化养殖中亟待解决的难题之一，制约了小尾寒羊养殖业的发展。良好的母性行为投入是提高多胎羔羊成活率的关键，然而，目前关于小尾寒羊对多胎羔羊个体母性行为投入差异及其内分泌、分子机制尚不清楚。因此，本项目以产2-3羔初经产母羊为研究对象，通过母性行为投入观测，明确母性行为投入差异及与羔羊生长的关系；通过母羊血浆中雌二醇、催产素、皮质醇水平检测，解析与母性行为投入密切相关的激素；进而探讨激素作用的相应受体DNA甲基化，揭示DNA甲基化与受体基因表达的关系。综合分析以上研究结果，从行为—内分泌—分子水平系统阐述小尾寒羊母性行为投入差异及其调控机制，为提高羔羊成活率，改善动物行为性状提供理论依据。

早期母子关系的建立是保障羔羊及时吃上初乳，促进羔羊成活的关键因素，良好的母性行为以及羔羊的哺乳行为可促进母子关系的建立。小尾寒羊是世界著名的高产绵羊品种，产羔多，但羔羊成活率低，为此，本项目从行为学角度研究小尾寒羊母性行为及羔羊哺乳行为的影响因素及神经内分泌学调控机制，并分析与羔羊生长的关系，主要得出以下结论：经产母羊母性行为优于初产母羊，并于体内催产素水平有关；产双羔母羊母性行为优于产单羔母羊，且与体内催产素、去甲肾上腺素、多巴胺、NO、γ-氨基丁酸水平有关；产母羔母羊母性行为优于产公羔母羊，与体内催产素水平有关；母羊母性行为的表达与羔羊体重呈正相关。与初产母羊的羔羊相比，经产母羊的羔羊站立更早、哺乳更频繁，体内生长激素和胆囊收缩素含量更高，且与羔羊体重呈正相关；与母羔相比，公羔尝试站立和哺乳的时间更早，每次哺乳持续时间更长，体内生长激素和内源性阿片类含量更高，并与羔羊体重呈正相关。产双胎经产母羊对第一羔和第二羔的母性行为投入均多于初产母羊，并于体内催产素、去甲肾上腺素、NO和GABA有关；产双胎公母羔的母羊对母羔的母性行为投入多于公羔。经产母羊大脑C-fos mRNA表达显著高于初产母羊，初产母羊下丘脑OTR mRNA表达显著高于经产母羊，ESR2、CRF、Zif/268、PR和GR mRNA表达初经产母羊间无显著差异。综上，胎次、产羔数和羔羊性别影响小尾寒羊母性行为，并受体内催产素、NA、DA、NO和GABA的调控，与羔羊体重呈正相关；胎次和羔羊性别影响小尾寒羊羔羊哺乳行为，并受体内生长激素、胆囊收缩素和内源性阿片肽调控，与羔羊体重呈正相关；胎次和羔羊性别可影响产双胎小尾寒羊母性行为投入，并受体内催产素、去甲肾上腺素、NO和GABA的调控，与羔羊体重无显著相关。