Heat Stress: A Serious Disruptor of the Reproductive Physiology of Dairy Cows

Global warming is a significant threat to the sustainability and profitability of dairy sector, not only in tropical or subtropical regions but also temperate zones where extreme summer temperatures have become new challenging reality. Prolonged exposure cows high compromises animal welfare, increases morbidity, suppresses fertility, resulting devastating economic losses for farmers. To counteract deleterious effects heat stress, cattl e employ various adaptive thermoregulatory mechanisms including molecular, endocrine, physiological, behavioral responses. These adaptations involve immediate secretion shock proteins cortisol, followed by complex network disrupted metabolic reproductive hormones such as prolactin, ghrelin, ovarian steroid, pituitary gonadotrophins. While strategic stress mitigation measures can restore milk production through modifications microclimate nutritional interventions, fertility records remain at low levels compared those thermoneutral periods year. This because sustainment multifaceted process that requires appropriate energy balance, undisrupted mode sustain maturation fertilizing competence oocyte, normal development early embryo unhampered maternal—embryo crosstalk. In this review, we summarize major molecular endocrine responses elevated cows, well impacts on maturing oocytes embryos, discuss consequences brings about cattle fertility.