Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review

SIMPLE SUMMARY: Heat stress is a significant threat to the pigs’ production performance as it greatly affects various body systems, particularly those that are responsible for nutrient digestion and absorption. Heat-stress-induced stressors such as oxidative stress threaten the integrity and functionality of the intestine by negatively affecting its morphology and histology through reduction of villus height, crypt depth, villus height to crypt depth ratio, mucosal surface and villi sloughing. Its protective function is also compromised as heat stress negatively influences the expression of tight junction proteins and disrupts the tight junction barrier function, leading to endotoxemia. These adverse effects of heat stress can be highly mitigated by supplementing dietary antioxidants, as these substances positively influence the intestinal integrity and function of pigs through the improvement of intestinal morphology and histology. Reduction of blood endotoxin through improved tight junction barrier function and depletion of oxidative stress with enhanced mucosal antioxidant capacity is also evident upon such supplementation. ABSTRACT: Heat stress (HS) significantly affects the performance of pigs by its induced stressors such as inflammation, hypoxia and oxidative stress (OS), which mightily strain the intestinal integrity and function of pigs. As heat stress progresses, several mechanisms in the intestinal epithelium involved in the absorption of nutrients and its protective functions are altered. Changes in these mechanisms are mainly driven by cellular oxidative stress, which promotes disruption of intestinal homeostasis, leading to intestinal permeability, emphasizing intestinal histology and morphology with little possibility of recovering even after exposure to HS. Identification and understanding of these altered mechanisms are crucial for providing appropriate intervention strategies. Therefore, it is this papers’ objective to review the important components for intestinal integrity that are negatively affected by HS and its induced stressors. With due consideration to the amelioration of such effects through nutritional intervention, this work will also look into the capability of dietary antioxidants in mitigating such adverse effects and maintaining the intestine’s integrity and function upon the pigs’ exposure to high environmental temperature.