Impact of chronic stress on reproductive functions in animals

Abstract

Chronic stress is a widespread condition with a profound negative impact on animal reproductive functions such as fertility, pregnancy and offspring production. The persistent activation of the hypothalamic-pituitary-gonadal (HPG) axis under chronic stress conditions leads to hormonal imbalances as elevated cortisol levels can suppress the reproductive hormone secretion. Hormonal imbalances adversely affect key reproductive processes such as ovulation, spermatogenesis, fertilization and embryo development. In livestock, these impairments significantly reduce reproductive efficiency, hence contributing to substantial economic losses in animal production systems. Furthermore, chronic stress induces oxidative stress, resulting in cellular damage to reproductive tissues and modulating immune system function, exacerbating the decline in reproductive health. Stressors which result into significant impact on animal production in daily basis are from poor managemental conditions, amongst which heat stress due to global climate change. All these stressors have compounded to reproductive challenges imposed by chronic stress. Heat stress, driven by higher ambient temperatures, further disrupts reproductive processes by altering hormonal balance, reducing gamete quality, impairing embryo survival and increasing pregnancy complications. The synergistic effect of chronic stress and heat stresses creates an additional burden on reproductive functions, particularly for less heat-intolerant livestock. This review critically explores the multifaceted mechanisms by which chronic stress disrupts reproductive function in animals, emphasizing the roles of hormonal dysregulation, oxidative stress and immune system alterations. Thus, addressing both environmental and physiological factors is of utmost importance to improve the reproductive functions of domestic animals. Highlights  Chronic stress disrupts the HPG axis, causing hormonal imbalances that impair fertility in animals.  Elevated glucocorticoids from chronic stress inhibit gonadal hormones, reducing reproductive success.  Understanding the impact of chronic stress on reproduction aids welfare in conservation and management.