Emerging paradigms in the aetiology of hyperthermia

A new paradigm for the aetiology of heat stroke in humans has emerged recently, which invokes the possibility of novel approaches to the treatment and prevention of heat stress in livestock species. Exposure to heat results in redistribution of blood to the periphery and compensatory reduction in the blood supply to the gut, which damages cells lining the gut, permitting endotoxin to enter the body. Endotoxin causes tissue damage and an acute–phase immune response. When blood supply resumes, reactive oxygen species and cytokines are released and cause multiple organ injury. Available evidence from livestock species is concordant with this paradigm. The possibility that the integrity of the gut lining is critical to resilience against hyperthermia has great significance for livestock species because energy–dense production diets are known to damage the gut lining. Betaine would impact beneficially at several critical points in the progression of thermally induced tissue damage. These include amelioration of damage to gut and liver tissue, and protection against the effects of endotoxin. It is proposed that administration of betaine to livestock would not only ameliorate losses in heat–stressed animals but also render them more resilient to heat.