Selecting Thermotolerant Animals as a Strategy To Improve Fertility In Holstein Cows

Abstract

The objective of this review is to approach current information on the effects of heat stress on the embryo and cow´s fertility and the selection of heat tolerant animals as a strategy to improve fertility and diminish the deleterious effects of heat stress. Heat stress decreases fertility by diminishing quality of oocytes and embryos through direct and indirect effects. Furthermore cows submitted to heat stress show decreased hormone secretion, reduced folliculogenesis, endometrial alterations and increased secretion of cytokines. These effects are exacerbated in high producing lactating cows due to their intense metabolism. The identification of molecular markers to thermotolerance in high producing lactating cows would allow an improvement in fertility without relinquishing on their milk production. Several single nucleotide polymorphisms (SNPs) have been identified and associated to heat tolerance. These SNPs could be the key to divert from the reduction on fertility and economical losses that the milk industry is suffering due to heat stress.