Shock D A, LeBlanc S J, Leslie K E, Hand K, Godkin M A, Coe J B, Kelton D F
Department of Population Medicine, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.
Strategic Solutions Group, Puslinch, Ontario, Canada, N0B 2J0.
J Dairy Sci. 2016 Mar;99(3):2169-2179. doi: 10.3168/jds.2015-9795. Epub 2016 Jan 6.
High ambient heat and humidity have profound effects on the production, health, profitability, and welfare of dairy cattle. To describe the relationship between summer temperature and relative humidity in the barn and determine the appropriateness of using meteorological station data as a surrogate for on-farm environmental monitoring, a study was conducted on 48 farms in Ontario, Canada, over the summer (May through September) of 2013. Within-barn environmental conditions were recorded using remote data loggers. These values were compared with those of the closest official meteorological station. In addition, farm-level characteristics and heat-abatement strategies were recorded for each farm. Environmental readings within the barn were significantly higher than those of the closest meteorological station; however, this relationship varied greatly by herd. Daily temperature-humidity index (THI) values within the barn tended to be 1 unit higher than those of the closest meteorological station. Numerically, 1.5 times more mean daily THI readings were in excess of 68 (heat stress threshold for lactating dairy cows) in the barn, relative to the closest meteorological station. In addition, tiestalls, herds that were allowed access to pasture, and herds that had no permanent cooling strategy for their cows had the highest mean and maximum daily THI values. Minimum daily THI values were almost 4 units higher for tiestall relative to freestall herds. Overall, due to farm-specific and unpredictable variability in magnitude of environmental differences between on-farm and meteorological station readings, researchers attempting to study the effects of environment on dairy cows should not use readings from meteorological stations because these will often underestimate the level of heat stress to which cows are exposed.
高环境温度和湿度对奶牛的生产、健康、盈利能力和福利有着深远影响。为了描述牛舍夏季温度与相对湿度之间的关系，并确定使用气象站数据作为农场环境监测替代数据的适用性，2013年夏季（5月至9月）在加拿大安大略省的48个农场进行了一项研究。使用远程数据记录器记录牛舍内的环境条件。将这些值与距离最近的官方气象站的值进行比较。此外，记录了每个农场的农场层面特征和防暑策略。牛舍内的环境读数显著高于距离最近的气象站的读数；然而，这种关系因牛群而异。牛舍内的每日温度湿度指数（THI）值往往比距离最近的气象站的THI值高1个单位。从数值上看，相对于距离最近的气象站，牛舍内平均每日THI读数超过68（泌乳奶牛的热应激阈值）的数量是其1.5倍。此外，拴系牛栏、允许进入牧场的牛群以及没有为奶牛制定永久降温策略的牛群，其每日THI的平均值和最大值最高。拴系牛栏的每日THI最小值相对于散栏牛群几乎高4个单位。总体而言，由于农场与气象站读数之间环境差异大小存在特定于农场且不可预测的变异性，试图研究环境对奶牛影响的研究人员不应使用气象站的读数，因为这些读数往往会低估奶牛所面临的热应激水平。
