ISSUE FOCUS 42 FEED & ADDITIVE MAGAZINE July 2023 “Ruminants’ prolonged exposure to high heat conditions results in significant changes in the physiological and biochemical parameters in the animal, making heat stress one of the most concerning issues facing producers. This is particularly relevant in the case of high-producing dairy cows. Mitigating heat stress is crucial to achieving efficient, profitable and sustainable animal agriculture operations.” CLIMATE CHANGE AND HEAT STRESS IN RUMINANTS Farm animals are commonly exposed to various stressors that can negatively affect their health and well-being. Heat stress is a condition in which the body has problems dissipating excess heat, impacting animal function, including growth, health, digestibility, lactation and reproduction (Wang, J., Li, J., Wang, F. et al., 2020). Although most common during summer months, a heat wave can occur at any period of the year, with significant effect when animals are not adapted to changes in ambient temperature, relative humidity, wind speed and solar radiation (Habeeb, A.A. et al., 2018). Heat stress is one of the most significant stressors at a time when ever-changing climate conditions are impacting ruminants of all sizes, from sheep and goats to beef and dairy cattle. While detrimental to all agriculturally important species, effects on the dairy industry are the most economically severe (St-Pierre et al., 2003). Analysts have noted rising cattle mortality rates because of heat waves in the mid-central United States (5-10% in July 1995, Hahn, 1999) and France (12-24% during 2003 and 2006, Morignat et al., 2014). An animal's thermoneutral zone (TNZ) is the temperature range in which they don’t have to expend energy to maintain normal body temperature. For healthy cattle, that range depends on a variety of factors, including breed, age, adaptation or animal status, among others, and is influenced by other environmental conditions such as relative humidity and wind velocity. For example, a lactating dairy cow’s TNZ is in the range of 5° to 25°C (Kadzere et al., 2002). Above 25°C, the animal must modify physiology and behavior. Consequently, animal productivity and feed efficiency decrease. Despite remarkable advances in the construction and design of animal housing facilities and cooling technology, high heat events are a costly issue for the dairy industry [estimated at $900 million annually in the United States (St-Pierre et al., 2003)]. HOW DOES HEAT STRESS IMPACT RUMINANT PERFORMANCE? Nicolas Cirier Ruminant Technical Sales Support – EMEA ADM Animal Nutrition
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