ISSUE FOCUS 34 FEED & ADDITIVE MAGAZINE July 2022 In warm blooded animals normal physiological processes require certain limits of ambient temperature. The temperature range in which farm animals feel comfortable and are able to give maximal productivity is called the thermoneutral zone. The mechanisms of body thermoregulation in young animals are not fully developed, meaning that their thermoneutral zone is narrower compared to adults. Elevation of ambient temperature beyond the thermoneutral zone complicates maintaining normal body temperature and leads to changes in metabolism and heat stress. As a consequence, productivity, fertility and health status of farm animals are negatively affected. The harmful effects of high ambient temperatures are enhanced by high humidity and insufficient air flow. The so-called temperature and humidity index (THI) is used in dairy cows to estimate the effective temperature based on ambient temperature and relative humidity values. When the THI exceeds 72, cows suffer heat stress. Modern breeds of farm animals are highly productive, but they have a high basic metabolic rate making them more sensitive to the extreme heat. For example, milk production of dairy cows was doubled in the last 50 years and this requires more intensive ways for cooling in hot weather. Nowadays, high-productive milking cows are affected by THI values less than 72. To maintain normal body temperature in heat stress conditions cows try to increase heat output by panting, sweating and dilation of blood vessels in the skin. At the same time, for reducing heat increment, cows HEAT STRESS IN DAIRY COWS CAN BE MITIGATED “Modern breeds of farm animals are highly productive, but they have a high basic metabolic rate making them more sensitive to the extreme heat. For example, milk production of dairy cows was doubled in the last 50 years and this requires more intensive ways for cooling in hot weather. Nowadays, highproductive milking cows are affected by THI values less than 72.” Diego Parra EMEA Technical Manager AB Vista Dimcho Djouvinov EMEA Technical Manager AB Vista
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