The role of melatonin in alleviating summer heat stress in livestock: Implications for productivity and reproduction

Heat stress is often underestimated, but it incurs a significant negative impact on animal industry. Livestock's performance is negatively impacted by high temperatures and humidity, limiting their genetic potential. This stress affects various bodily functions, including heat regulation and energy maintenance. Consequently, animals experience reduced feed intake, disruptions in protein and energy metabolism and imbalances in hormones, leading to decreased productivity and reproductive problems. To mitigate heat stress in livestock, common methods involve providing sheds, fans and evaporative cooling or adjusting their feed. However, these approaches have limitations, necessitating the exploration of alternative solutions. Melatonin, known for its role in regulating reproduction based on the season, can effectively alleviate summer stress by influencing evaporative heat loss and the cardiovascular system. It also interacts with other hormones, such as thyroxine and modifies adrenal function. The effects of heat stress can be observed through changes in physiological parameters like rectal temperature, pulse and respiratory rate. Blood parameters such as erythrocyte count, PCV (packed cell volume) and haemoglobin value are also affected with lower than normal concentrations of triiodothyronine and thyroxine under heat stress conditions. However, supplementing with melatonin can help counteract the effects of heat stress by regulating biomarkers of oxidative stress and total antioxidant capacity. Understanding melatonin's role in mitigating summer stress can aid in developing effective strategies to improve livestock productivity and reproduction during challenging weather conditions. Further research on melatonin's role in alleviating summer stress is crucial to develop more efficient approaches to minimise the negative effects of heat stress on livestock productivity and reproduction, ultimately benefiting the livestock industry.