This article discusses the effect of negative energy balance on the metabolic changes during postpartum period and its impact on the reproductive potential of high yielding dairy cows and beef cows. Metabolic changes alters the growth hormone, IGF, insulin and leptin secretions, along with losses in body condition scores of cows that leads to cyclic irregularities in cows. Negative energy balance directly impairs the reproductive function and embryonic quality of both dairy and beef cows. Different strategies to minimize the adverse effects of negative energy balance on the reproductive performance of the cows are also presented.