牛热应激的综述,Australian Veterinary Journal

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牛热应激的综述
Australian Veterinary Journal ( IF 1.3 ) Pub Date : 2023-08-24 , DOI: 10.1111/avj.13275
R W Shephard ₁ , S K Maloney ₂

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牛在不同的气候条件下将体温控制在一个狭窄的范围内。内源性体热是由新陈代谢、消化和活动产生的。辐射是牛体内热量传递的主要外部来源。牛恒温利用行为和生理控制来管理身体与环境之间的辐射、对流、传导和蒸发热交换，指出蒸发机制几乎完全将身体热量传递到环境中。牛通过寻求遮荫（热）和庇护所（冷）以及通过挤在一起或站得更远来控制辐射，并注意到辐射传输潜力存在固有的品种和年龄差异。皮肤与外部环境之间的温度梯度和风速（对流）决定了这些方式的热传递。牛通过管理流向周围的血液（生理学）、短期（行为上）寻找庇护所和站立/躺着活动以及长期（适应）改变皮毛和调整代谢率来控制这些机制。牛的蒸发热损失主要来自出汗，还有一些呼吸贡献，是当环境温度超过皮肤温度（~36°C）时散发多余热量的主要机制。牛往往更能适应较冷的外部条件，而不是较热的外部条件，而印度牛品种比金牛牛更能适应较热的条件。管理可以通过确保适当品种、适当适应环境的牛、适当的饲养密度、饲喂适当的饮食（和水）以及获得适当的庇护所和通风来更好地适应其预期的农场环境，从而最大程度地减少热应激风险。

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A review of thermal stress in cattle

Cattle control body temperature in a narrow range over varying climatic conditions. Endogenous body heat is generated by metabolism, digestion and activity. Radiation is the primary external source of heat transfer into the body of cattle. Cattle homeothermy uses behavioural and physiological controls to manage radiation, convection, conduction, and evaporative exchange of heat between the body and the environment, noting that evaporative mechanisms almost exclusively transfer body heat to the environment. Cattle control radiation by shade seeking (hot) and shelter (cold) and by huddling or standing further apart, noting there are intrinsic breed and age differences in radiative transfer potential. The temperature gradient between the skin and the external environment and wind speed (convection) determines heat transfer by these means. Cattle control these mechanisms by managing blood flow to the periphery (physiology), by shelter-seeking and standing/lying activity in the short term (behaviourally) and by modifying their coats and adjusting their metabolic rates in the longer term (acclimatisation). Evaporative heat loss in cattle is primarily from sweating, with some respiratory contribution, and is the primary mechanism for dissipating excess heat when environmental temperatures exceed skin temperature (~36°C). Cattle tend to be better adapted to cooler rather than hotter external conditions, with Bos indicus breeds more adapted to hotter conditions than Bos taurus. Management can minimise the risk of thermal stress by ensuring appropriate breeds of suitably acclimatised cattle, at appropriate stocking densities, fed appropriate diets (and water), and with access to suitable shelter and ventilation are better suited to their expected farm environment.

更新日期：2023-08-24

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