ISSUE FOCUS FEED & ADDITIVE MAGAZINE July 2025 49 butyrate. These VFAs are absorbed through the rumen wall and are used by the cow as a primary source of energy, generating more heat through processing, particularly during gluconeogenesis in the liver. This makes the cow a true “thermal power station on four legs.” WHEN SUPERPOWERS FAIL Although a biomechanical masterpiece, the dairy cow is vulnerable to high ambient temperatures. As soon as the temperature rises, her finely tuned balance of heat production and loss is disrupted, and the consequences can be severe. Heat stress—the invisible kryptonite of dairy cows worldwide—has a significant impact on their health, welfare, and production. Thermoregulation is the process of maintaining core body temperature within a narrow range and is thought to optimize organ and system function. Homotherms, such as cows, control the exchange of heat between their body and the environment so that the heat gained from metabolism is balanced by the heat lost to the environment (Figure 2). In this way, body temperature remains stable. The relationship between core body temperature and the temperature of the environment can be described in terms of several zones that distinguish different physiological responses. The narrowest zone is the thermoneutral zone (TNZ). BACTERIA PROTOZOA FUNGI Figure 1. The rumen is home to a wide variety of bacterial, fungal, and protozoal species. All these make up the rumen microbiome HEAT GENERATED HEAT LOST RADIATION EVAPORATION CONVECTION CONDUCTION GESTATION FEED INTAKE ACTIVITY GROWTH LACTATION MAINTENANCE METABOLISM Figure 2. To maintain thermal energy balance, heat generated by metabolism (maintenance, activity, growth, lactation, gestation, and feed intake) must be compensated for by heat lost to the environment. This thermal balance cannot be maintained if an animal does not give off enough heat
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