Abstract: With the intensification of milk production, cow productivity has increased dramatically and milk production is increasing, however, the fertility of high-yielding cows is decreasing, which is associated with postpartum energy imbalance in cows. A negative energy balance occurs when a cow's postpartum energy requirements exceed her energy intake. Studies have shown that negative energy balance affects cow fertility through multiple mechanisms, including changes in endocrine and metabolic mechanisms in cows caused by negative energy balance. Therefore, this paper provides an overview of the effects of negative energy balance on cow fertility and the endocrine and metabolic mechanisms by which negative energy balance leads to reduced fertility in cows, with the aim of providing a reference for the development of methods to mitigate negative energy balance with the aim of reducing the losses caused by negative energy balance in animal husbandry.

Key words: negative energy balance, cows, reduced fertility, mechanism