Adaptive Mechanisms and Mitigation Strategies of Dairy Cattle to Heat Stress
Heat stress is one of the most important factors limiting dairy production,and has a major impact on the productivity,health,reproduction and welfare in dairy cows.These adverse effects on dairy cows can be fatal as heat stress increases.Increasing global warming exacerbates the negative effects of heat stress on livestock animals.Animals are able to respond to changing environments by altering their phenotypic and physiological characteristics,and survive depending on their ability to cope or adapt to environmental conditions.Cows are thermostatic animals that respond and adapt to heat stress by reducing production of metabolic heat and thermoregulation at the expense of productivity to some extents.In this article,we reviewed the adverse effect of heat stress on lactation of dairy cows.The reduced lactation performance under heat stress were analyzed from the perspective of oxygen balance.The adaptive mechanism of dairy cows to heat stress was reviewed from the perspectives of heat shock protein production and endocrine regulation.Finally,the mitigation strategies to cope with heat stress were summarized in terms of environmental control and nutritional regulation.