Effect of heat stress on pig production and its mitigation strategies: a review

Heat stress (HS) poses a significant challenge to pig production worldwide, with far-reaching consequences for productivity, reproduction, and overall animal welfare. Stress, broadly defined as the nonspecific physiological response to environmental demands, disrupts homeostasis, leading to health imbalances, behavioral changes, and reduced productive efficiency. Pigs are particularly susceptible to HS due to their limited thermoregulatory capacity, influenced by a low density of functional sweat glands and a thick subcutaneous fat layer. Rising global temperatures have exacerbated HS-induced economic losses in the swine industry, manifesting as decreased growth rates, poor reproductive performance, reduced feed efficiency, increased morbidity, and mortality. HS impairs pig production by diminishing feed intake and nutrient availability, which leads to reduced growth, suboptimal carcass quality, and compromised reproduction. Sows experience increased anestrus, extended weaning-to-estrus intervals, and smaller litter sizes, while boars exhibit reduced semen quality and fertility. The genetic selection for higher productivity has inadvertently lowered heat tolerance, as metabolic heat production increases with improved production traits. Furthermore, inadequate environmental management in pig housing exacerbates the impact of HS. Variations in heat tolerance among pigs underscore the importance of understanding genetic, physiological, and environmental factors influencing their response to HS. Research reveals genetic differences in thermotolerance, offering potential avenues for selective breeding to improve resilience. Effective management strategies, including nutritional adjustments, environmental modifications, and genetic selection, are crucial for mitigating the negative effects of HS and enhancing pig productivity. This review highlights the multifaceted impacts of HS on swine production, explores the physiological and reproductive consequences, and discusses adaptive and ameliorative measures to address these challenges, with a focus on maintaining sustainable pig production in the face of climatic changes.