Dairy Cow Heat Stress Within Building Microclimates

由于奶牛的高代谢率，哺乳奶牛会产生大量的体温。多余的热量必须被驱散，如果不这样做，就会导致热应激。奶牛理想的环境温度在5-25摄氏度之间，但这受品种、饲养水平、生产和其他个别因素的影响；低至20摄氏度的温度可能会导致某些奶牛出现热应激。这种情况在英国夏天很常见，甚至在冬天也会发生，特别是在室内。热压力已经是英国许多农场的一个问题，但预计气候变化导致的平均气温上升以及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，包括饲料摄入量和产奶量减少，生育能力和免疫功能受损，所有这些都对奶牛的福利和奶牛养殖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，寻找阴凉处或通风较好的地方，或者表现出其他个人和社会行为反应。并不是所有的奶牛都表现出明显的热应激体征，因此监测通常基于替代测量，如当地气象站的温度和湿度记录，或来自几个室内传感器的测量。然而，包括我们团队在内的最近的研究表明，谷仓内的温度、湿度和通风具有很大的时空变化，既受建筑设计和使用的影响，也受外部条件的影响。这些牛舍“小气候”的存在意味着奶牛经历了不同的个体特定条件，这些条件随着时间和空间的不同而变化，这将影响它们应对热应激的能力(因此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和直接影响：我们有证据表明，在室内饲养的奶牛随着温度的升高而在空间上聚集，这是一种潜在的不适应反应，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来以前所未有的详细程度记录整个奶牛群在不同的温度条件和室内小气候下的运动、活动和空间利用模式。将在主要研究农场(雪松、雷丁)收集为期12个月的数据，并在6个不同建筑设计和用途的案例研究农场收集夏季和冬季较短时间的数据。对牛舍小气候(温度、湿度、空气质量)的持续传感器监测和详细的通风调查将与生理测量(体温、生产、健康)相结合，以详细分析室内饲养的奶牛在不同时间段如何应对和应对热应激。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奶牛的行为，以及这些微气候如何影响奶牛的行为。我们将与农民研究小组直接合作，以参与性的方式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.