Effects of heat stress on ruminant physiological changes in dry arid regions: a review

Abstract

Heat stress in ruminants can have a profound effect on their bodies. Every part of the body is affected in some way, and it’s an entirely caused systemic disorder. The characteristics of the animal, the environment, and the way the animal is managed all have an effect on the type and magnitude of the reaction. The development of effective measures to address heat stress (HS) has proven challenging due to the complex nature of the stress and the diverse array of ruminant production systems. The present matter has acquired significant urgency due to the ongoing expansion of the global economy and the concurrent rise in global temperatures.
The objective of this study was to examine the physiological mechanisms employed by ruminant animals inhabiting arid and semi-arid regions in order to mitigate the effects of HS. The responses provided can be categorized into three distinct groups: the reduction of feed intake to decrease the production of metabolic heat, the enhancement of heat-loss capacity, and the activation of hormones, enzymes, and genes associated with heat tolerance. In light of HS, ruminant animals exhibit a decrease in their level of physical activity, feed consumption, and rumination, while concurrently increasing their water consumption, evaporative loss through sweating, respiration, panting, and rectal temperature (RT), in the specified sequence. The increased dissipation
of heat caused by perspiration in ruminants would have made it unnecessary to have an elevated respiration rate. In order to meet the demands of perspiration and minimize the risk of respiratory alkalosis resulting from alveolar ventilation in the lungs, it is crucial to optimize the utilization of water and minerals in ruminant animals. Hormonal levels in the bloodstream are diminished due to HS, specifically affecting anabolic hormones like growth hormone, cortisol, triiodothyronine, and thyroxine.
Ruminants exhibit discernible inclinations towards specific types of shade structures, contingent upon the characteristics of their immediate surroundings. Therefore, it is crucial to take these preferences into account when making well-informed decisions regarding heat mitigation strategies in agricultural environments. In conclusion, HS has a negative impact on ruminant physiology that reflects on productivity and welfare. With a better understanding of how HS affects livestock, researchers can come up with ways to manage it and show the need for more research on the topic of HS in livestock.