British Cattle Veterinary Association

Along with increasing milk yield, modern dairy cows have become less fertile. Poorer ovarian functioning with disturbed ovulations together with reduced oocyte and embryo quality are recognized as major factors in this problem of disappointing fertility outcome. Changes in follicular growth patterns during a period of negative energy balance (NEB) can indirectly affect oocyte quality. The endocrine and biochemical changes, which are associated with NEB, are reflected in the microenvironment of the growing and maturing female gamete, and may result in the ovulation of a developmentally incompetent oocyte.