Effects of Heat Stress on Metabolism in Ruminants

Heat stress is an important factor influencing animal welfare negatively, decreasing efficiency in dairy production, leading to economic loss by increasing health problems. Appropriate description of animals experiencing heat stress and comprehension of biological mechanism(s) of heat stress causing a decline in milk synthesis, growth and reproductive indices may contribute for development of new approaches in minimising low efficiency during stressful summer months and in sustaining efficiency. The biological mechanism of heat stress is partly explained by reduced feed intake. At the same time, heat stress alters endocrine status, causes reduction in rumination and in nutrient absorption, and increases maintenance requirements resulting changes in absorption of nutrients and utilisation of energy. It has been observed that there is thermal discrepancy between the utilisation of nutrients under heat stress conditions. Therefore, during heat stress all these aspects are presumably a mechanism to minimise metabolic heat production. In this paper, we discussed how animals respond to heat stress and how heat stress affects the metabolism and post-absorption of nutrients.