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Oxidative Stress and Reproductive Disorders in Dairy Cows

Oxidative stress seems to be implicated in the pathogenesis of reproductive diseases of dairy cows and subsequent decrease of animal fertility. A major role in the development of oxidative stress is a negative energy balance (NEB) which often occurs in late pregnancy and early lactation. During the NEB, there are metabolic changes accompanied with an increased production of reactive oxygen species (ROS). Although ROS are unavoidable products of normal metabolic processes and are not always harmful, they can impair health and reproductive performance of dairy cows. Mammalian cells possess a natural anti-oxidative system involving in the removal of reactive oxygen molecules and the repairing of oxidative damage. However, exceeded amount of reactive oxygen molecules may have direct and indirect effect on cow’s health. In particular, peroxidation of steroidogenic enzymes and steroid hormones can inactivate their function and directly impair reproduction. Additionally, NEB in the early postpartum period is related to endocrine disorders causing a decrease in LH pulse frequency, a decreased diameter of dominant follicles with low estradiol production and decreased systemic and intra-follicular IGF-I availability. These disorders lead to an increased interval to first estrus, poor oocyte quality and weak estrus expression making the detection of estrus even more difficult. As a consequence, ovary function is disturbed and reproductive performance is impaired. Reproductive diseases including cystic ovarian follicles, anestrus, retained placenta, endometritis and metritis present a great problem in dairy cow’s management. Clear understanding of pathophysiology of negative energy balance and oxidative stress could contribute to better approach to reproductive management of dairy cows avoiding reproductive diseases as much as possible.

oxidative stress, reproduction, dairy cows

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