Journal of Veterinary and Applied Sciences

Abstract
The reproductive performance of cows is significantly influenced by stress-induced cortisol release, especially in situations of physiological and environmental stress, like heat stress. The zona fasciculata of the adrenal cortex produces cortisol, a glucocorticoid hormone that is a major indicator of stress, and is mostly controlled by the hypothalamic-pituitary-adrenal (HPA) axis. The processes by which high cortisol levels negatively impact bovine reproduction are examined in this review. Increased cortisol concentration in the circulatory system impairs follicular development, ovulation and oestrus behaviour by blocking the secretion of gonadotropin-releasing hormone (GnRH) and gonadotrophins [luteinizing hormone (LH) and follicle stimulating hormone (FSH)], which upset the hypothalamic-pituitary-gonadal (HPG) axis. Cortisol affects steroidogenesis, lowers oocyte quality and modifies folliculogenesis at the ovarian level by interacting with glucocorticoid receptors. Furthermore, the important reproductive hormones like progesterone and oestradiol are suppressed by stress-induced cortisol which results in poor follicular maturation, decreased embryo viability and lower conception rates. Long-term stress especially heat stress, increases embryonic mortality and modifies gene expression linked to embryonic development thereby aggravating these consequences. In general, high cortisol levels negatively affect fertility by disrupting oocyte competence, hormonal balance and gestational processes. Developing efficient management techniques to reduce stress and increase the reproductive performance of cows requires an understanding of these mechanisms.

Keywords: Cattle (cows); Heat stress; Cortisol; Female reproduction; Folliculogenesis; Gonadotropin-releasing hormone.

How to cite this article:
Ornguga N (2026). Mechanisms of cortisol-mediated inhibition of reproductive hormones in heat stressed cows: A mini-review. Journal of Veterinary and Applied Sciences, 16(2): 1607 – 1617..

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