Improving ruminant nitrogen utilization is an effective measure to tackle global feed resource shortage, environment pollution and achieve sustainable development of animal husbandry. As is known to all, ruminants have an important regulation mechanism which is to allow ureaN recycle to the gastrointestinal tract, especially in the rumen. As a result, ureaN can be used as the nitrogen source of microbial protein synthesis and was a major contributor to provide small intestinal metabolism of protein. Based on the knowledge of metabolic characteristics of ruminants, the paper expounded the research progress home and abroad on improving ruminant nitrogen utilization from the aspects such as the effect of basal diet and rumen factors on nitrogen utilization, and the economic and ecofriendly integration technology.

Preserving the fresh semen at low temperature can prolong the survival period of sperm, improve the utilization of superior ram breeds and accelerate the breeding improvement, and in the preservation the diluent is the key to maintain and improve the quality of semen. The paper reviewed research on composition and effect of diluent and semen dilution ratio in goat semen cryogenic storage to provide certain reference for research on goat semen cryogenic storage and exert full useof superior ram breeds.

Major Histocompatibility Complex(MHC), further divided into Class I, II and III regions，is an organized cluster of tightlylinked genes widely distributed in the vertebrates. Owing to the high gene polymorphism, the ovine MHCⅡ has received increasing focus of study on genetics, evolution and breeding for disease resistance. The present study reviewed the recent advances of MHCⅡgene polymorphism and its disease association in different sheep breeds, and prescribed its research in the future.

Livestock industry in China have attained worldknown achievements in the 30 years' development since reform and opening up. However, its further progress met with problems and obstacles including low productivity, resources wastage, outdated breeds, product safety, disease,feed shortage, technique proficiency, environmental pollution, animal welfare and irrational adjustment from the government. The present study analyzed the above problems, put forward corresponding measures to solve and delivered a prospective preview on the future development of livestock induatry in China.