Reproductive efficiency in dairy cattle has been decreased over the last 5 decades despite significant gains in genetic selection, improved reproductive technologies and nutritional care. In high-yielding dairy cattle, the negative energy balance (NEB) during the first week post-partum adversely affects ovarian activity, mainly follicle growth and steroidogenesis. Circulating levels of non-esterified fatty acids (NEFAs) and urea are elevated during NEB and are known to be accumulated in the follicular fluid of dominant follicle where they exert adverse effect on oocyte maturation, leading to low fertilization rate and early embryonic development. This study aimed to review the literatures on the interaction between NEB, metabolic stress and reproductive performance of dairy cattle. In this review, the adverse effects of high circulating NEFAs, a biomarker of NEB and urea on oocyte maturation, embryonic quality and developmental and pregnancy outcomes is highlighted.
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