# From Systemic Stress to Ovarian Failure: Heat Stress-Induced Infertility in Pigs as a Model for Reproductive Dysfunction

## TL;DR

Heat stress disrupts reproduction in pigs by affecting hormones, metabolism, and ovarian function, offering insights into infertility in other mammals including humans.

## Contribution

This review provides a comprehensive analysis of systemic and ovarian mechanisms of heat stress-induced infertility in pigs.

## Key findings

- Heat stress impairs endocrine regulation, metabolism, and immune function, which are critical for reproduction.
- Oxidative stress, autophagy, and apoptosis pathways in the ovary are disrupted by heat stress, affecting follicular development and oocyte quality.
- Increased intestinal permeability during heat stress leads to inflammation, further compromising reproductive health.

## Abstract

Heat stress (HS) occurs when animals are unable to effectively dissipate excess body heat, leading to increased core temperature and physiological imbalance. In mammals, HS negatively affects female reproduction. Infertility associated with HS is well documented in swine and is increasingly recognized in other mammals, including humans. HS disrupts several systemic processes that are essential for normal reproductive function, including endocrine regulation, nutrient metabolism, immune activity, and intestinal barrier integrity. Reduced feed intake and changes in metabolic hormones such as insulin and prolactin can impair ovarian function. Increased intestinal permeability during HS may allow bacterial endotoxins to enter the bloodstream, triggering inflammation that further compromises reproductive physiology. At the ovarian level, HS alters key cellular pathways involved in cell survival and metabolism, including Janus Kinase/Signal Transducer and Activator of Transcription (JAK–STAT), Phosphoinositide 3-Kinase/Protein Kinase B (PI3K/AKT), oxidative stress responses, autophagy, apoptosis, and heat shock protein expression. These changes disrupt follicular development, hormone production, oocyte quality, and corpus luteum function, resulting in reduced conception rates and increased embryonic loss. This review summarizes current knowledge of systemic and ovarian mechanisms by which HS impairs female reproduction in pigs and identifies areas requiring further investigation to improve fertility under increasing environmental temperatures.