Dairy Cow Heat Stress Within Building Microclimates

泌乳奶牛由于其高代谢率而产生大量的体热。多余的热量必须消散，否则会导致热应力。奶牛的理想环境温度范围在5 - 25摄氏度之间，但这受到品种，饲养水平，生产和其他个体因素的影响;温度低至20摄氏度可能会导致某些奶牛的热应激。这种情况在英国夏天很常见，甚至在冬天也会发生，特别是在室内。热应激已经是许多英国农场的一个问题，但预计平均温度的上升以及气候变化导致的热浪的频率和持续时间，使这个问题变得更加紧迫。热应激可导致一系列生理问题，包括采食量和产奶量减少，生育力和免疫功能受损，所有这些都对奶牛福利和奶牛场的经济可持续性产生负面影响。众所周知，奶牛会调整自己的行为，以帮助科普高温和潮湿：它们可能会增加冷水的摄入量，寻求阴凉或通风良好的区域，或表现出其他个人和社会行为反应。并非所有奶牛都表现出明显的热应激体征，因此监测通常基于代理测量，例如当地气象站的温度和湿度记录，或来自一些室内传感器的测量。然而，最近的研究，包括我们的团队，表明谷仓内的温度，湿度和通风具有很高的时空变化，并受到建筑设计和使用以及外部条件的影响。这些牛舍“微气候”的存在意味着奶牛会经历不同的个体特定条件，随时间和空间而变化，这将影响它们科普热应激的能力（以及随后的生理和行为反应）。社会互动和社会层面的反应也可能受到室内微气候的影响，并直接影响室内微气候：我们有证据表明，在室内饲养的奶牛在空间上随着温度的升高而聚集，这是一种潜在的适应不良反应，因为社会聚集进一步增加了局部温度。在这个项目中，我们将使用位置跟踪技术以前所未有的详细程度记录奶牛的运动，活动，以及在不同的温度条件和室内小气候下对奶牛群的空间利用。将在主研究农场（CEDAR，阅读）收集12个月的数据，并在夏季和冬季在6个具有不同建筑设计和用途的案例研究农场收集较短时间的数据。连续传感器监测畜舍微气候（温度、湿度、空气质量）和详细的通风调查将与生理测量相结合（体温，生产，健康），以便详细分析室内饲养的奶牛如何应对，我们将使用建筑工程模拟方法来确定不同农场建筑环境中的室内微气候，管理系统，以及这些微气候如何影响，并受到影响，牛的行为。我们将直接与农民研究小组合作，采用参与式方法，评估一系列潜在的缓解策略，以减少当前和未来气候情景下的热应力影响。与我们的行业指导小组合作，我们将为英国乳制品行业提供预防和管理热应激的实用循证解决方案。

Lactating dairy cows generate a significant amount of body heat due to their high metabolic rates. Excess heat must be dissipated and a failure to do so leads to heat stress. The ideal ambient temperature for dairy cows ranges between 5 - 25 degree C, but this is affected by breed, feeding level, production, and other individual factors; temperatures as low as 20 degree C may lead to heat stress in some cows. Such conditions are common in the UK during summer, and can even occur in the winter, particularly indoors. Heat stress is already a problem on many UK farms, but predicted increases in average temperature and the frequency and duration of heat waves resulting from climate change, makes the issue even more urgent. Heat stress can result in a range of physiological problems including reduced feed intake and milk yield, and impaired fertility and immune function, all of which negatively affect cow welfare and the economic sustainability of dairy farms. Cows are known to adapt their behaviour to help cope with high temperatures and humidity: they may increase their intake of cold water, seek shade or areas of increased ventilation, or exhibit other individual and social behavioural responses. Not all cows show obvious physical signs of heat stress and hence monitoring has typically been based on proxy measures such as local weather station temperature and humidity records, or measurements from a few indoor sensors. However, recent research, including by our team, has shown that temperature, humidity, and ventilation within barns have high spatiotemporal variation, and are affected by both building design and usage, as well as external conditions. The presence of these barn 'microclimates' means that cows experience different individual-specific conditions, varying over time and space, that will influence their ability to cope with heat stress (and hence their subsequent physiological and behavioural responses). Social interactions and herd-level responses may also be affected by, and directly affect, the indoor microclimate: we have evidence that cows housed indoors spatially cluster with increasing temperature, a potentially maladaptive response since social clustering further increases localised temperatures.In this project we will use location tracking technology to record, in unprecedented levels of detail, patterns of movement, activity, and space-use of full herds of dairy cows under varying thermal conditions and indoor microclimates. Data will be collected for 12 months on the main study farm (CEDAR, Reading) and for shorter periods in summer and winter at 6 case-study farms with different building design and usage. Continuous sensor monitoring of barn microclimates (temperature, humidity, air quality) and detailed ventilation surveys will be combined with physiological measures (body temperature, production, health) to enable detailed analysis of how indoor-housed dairy cows respond to, and cope with, heat stress over different timescales.We will use building engineering modelling approaches to determine indoor microclimates in different farm building environments and management systems, and how these microclimates affect, and are affected by, cow behaviour. We will work directly with farmer study groups in a participatory approach to evaluate a range of potential mitigation strategies to reduce heat stress impacts under current and future climate scenarios. Working with our industry Steering Group, we will provide practical evidence-based solutions to the UK dairy industry for preventing and managing heat stress.