Abstract: Heat stress is non-specific response reactions of physiological activities to the high-temperature environment, which is detrimental to ruminant animals. Also, heat stress is an important stress-induced diseases which affect the production and reproduction of ruminants in summer. It has been researched a lot in recent years. The author makes a brief summary about the effects of heat stress on ruminant from the research in 2009, and it involves in milk yield, milk quality, physiology, plasma biochemistry and endocrine effects of heat stress, and the current main measures to alleviate heat stress.

Key words: heat stress; milk yield; milk quality; physiology; plasma biochemistry