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。多余的热量必须散发出去，否则就会导致热应激。奶牛的理想环境温度在5 - 25摄氏度之间，但这受品种、饲喂水平、产量和其他个体因素的影响；低至20摄氏度的温度可能会导致一些奶牛出现热应激。这种情况在英国夏天很常见，甚至在冬天也可能发生，尤其是在室内。热应激已经是英国许多农场面临的一个问题，但预计平均气温的上升以及气候变化导致的热浪频率和持续时间的增加，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，生育能力和免疫功能受损，所有这些都会对奶牛的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来帮助应对高温和潮湿：它们可能会增加冷水的摄入量，寻找阴凉处或通风更好的地方，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身体热应激迹象，因此监测通常基于代理测量，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，包括我们团队在内的最近研究表明，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。这些谷仓“微气候”的存在意味着奶牛会经历不同的个体特定条件，随着时间和空间的变化而变化，这将影响它们应对热应激的能力（从而影响它们随后的生理和行为反应）。社会互动和牛群水平的反应也可能受到室内小气候的影响，并直接影响室内小气候：我们有证据表明，奶牛在室内的空间聚集随着温度的升高，这是一种潜在的适应不良反应，因为社会聚集进一步提高了局部温度。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在不同温度条件和室内小气候下整群奶牛的运动、活动和空间使用模式。数据将在主要研究农场（CEDAR, Reading）收集12个月，并在夏季和冬季在6个具有不同建筑设计和使用方式的案例研究农场收集较短的时间。对畜棚小气候（温度、湿度、空气质量）的连续传感器监测和详细的通风调查将与生理测量（体温、产量、健康）相结合，以详细分析室内饲养的奶牛在不同时间尺度上对热应激的反应和应对。我们将使用建筑工程建模方法来确定不同农场建筑环境和管理系统中的室内小气候，以及这些小气候如何影响和受奶牛行为的影响。我们将以参与式的方式直接与农民研究小组合作，评估一系列潜在的缓解战略，以减少当前和未来气候情景下的热应激影响。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实用的循证解决方案，以预防和管理热应激。

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.