Strategies for increasing fertility in high productivity dairy herds

Over the years, the dairy cow has been selected and managed for high performance and efficiency in milk production. Thus, different factors influence the fertility of dairy cows of high productivity. It has been observed that genetic selection for large productions and metabolic adaptations may explain the greater requirement to maintain reproduction at satisfactory levels. Also, these animals are more susceptible to environmental factors such as increased temperature and humidity. Studies have shown that heat stress results in reduced estrous expression and impairs ovarian function, interfering with folliculogenesis and steroidogenesis. Likewise, under heat stress conditions, dry matter intake is reduced, prolonging the after calving negative energy balance and calving-conception interval. Thus, suboptimal reproductive performance is one of the main factors responsible for the economic losses in large dairy farms. In this context, numerous management practices have been introduced to improve reproduction in high productivity animals, making reproductive management increasingly complex in dairy farms. Among them, we can mention the implementation of management and nutrition conditions adapted to the periods of heat stress, as well as protocols and biotechniques that improve the quality of the follicles and oocytes. Thus, because genetic selection for better fertility animals is a characteristic of low heritability, the success of reproductive programs in highly productive herds depends on the association of the control of genetic and physiological factors with those of environmental, nutritional and management. This paper aims to discuss reproductive aspects of dairy cows of high productivity, the role of heat stress in this context, and the implementation of management, nutrition and biotechnology conditions, to minimize the adverse effects on the reproduction of these animals.