USE OF REPRODUCTIVE BIOTECHNOLOGIES TO IMPROVE THE FERTILITY OF REPEAT-BREEDER AND HEAT-STRESSED DAIRY COWS

Abstract

Cows that do not become pregnant during early lactation after successive inseminations are usually classified as repeat-breeder cows. Furthermore, heat stress has a pronounced deleterious effect on fertility in dairy herds throughout the world, especially in hot and humid summer months in tropical and subtropical areas. Studies describes the detrimental effect of heat stress on reproduction, with emphasis on carry over effects of heat stress on oocyte quality, embryo development and P/AI. Additionally, lower fertilization rate is also an important characteristic associated with repeat-breeder cows. In repeat-breeder cows, decreased fertility has been related to a deleterious effect on oocyte quality. Thus, the fertility problems observed in repeat-breeder and heat stress cows may be related to poor oocyte quality associated with a metabolic status. Studies support thar embryo transfer can be a practical and effective solution to achieve pregnancy in repeat-breeder and heat-stressed dairy cows (with reduced oocyte quality and fertility to insemination).