Evaluation of environmental parameters in a microregion in southern Amazonas State, Brazil, and their relationship with heat stress in dairy cattle

Abstract Environmental thermal comfort provides higher efficiency in the exploitation of dairy farming, as the responses of animals to the environment are decisive in the activity’s success. This study aimed to evaluate heat stress in dairy cows in the municipality of Humaitá, located in the south of theAmazonas State (AM), Brazil.Air temperature (TA) and relative humidity (RH) data were used to calculate the temperature humidity index (THI) in the dry (August 2020) and rainy seasons (January 2021). The August data were collected at the automatic weather station belonging to the National Institute of Meteorology. The January data were collected by a Hobo® U23-001 thermo-hygrometer installed at Fazenda Nossa Senhora Aparecida. The hourly and monthly means of the data were calculated and, subsequently, boxplots were plotted. TA and RH were 0.65 °C and 0.64% below the provisional climatological normal (PCN), respectively, for August, while January presented 0.77 °C and 3.61% above the PCN, respectively. THI values ranged from 56.25 (comfortable) to 84.68 (emergency) in August and 74.15 (comfortable) to 84.07 (emergency) in January. The maximum THI was observed in August, as well as the largest range. The results allow inferring that heat stress in dairy cows in the municipality of Humaitá-AM presents a state of alert even for cross-breed animals. Thus, the use of shading in pastures is suggested to minimize the effect of heat stress on the productive performance of the animals.

摘要：环境热舒适度可提升奶牛养殖业的生产效率，动物对环境的响应是养殖活动成败的关键所在。本研究旨在评估位于巴西亚马逊州（Amazonas State, AM）南部乌马伊塔市（Humaitá）的奶牛热应激（heat stress）状况。本研究采用气温（Air Temperature, TA）与相对湿度（Relative Humidity, RH）数据，对该地区旱季（2020年8月）与雨季（2021年1月）的温度湿度指数（Temperature Humidity Index, THI）进行计算。2020年8月的气象数据由巴西国家气象局（National Institute of Meteorology）下属的自动气象站（automatic weather station）采集；2021年1月的数据则由安装在法曾达·诺萨·塞努拉·阿帕雷西达（Fazenda Nossa Senhora Aparecida）牧场的Hobo® U23-001型温湿度记录仪（thermo-hygrometer）采集。随后对数据的逐小时与逐月平均值进行计算，并绘制箱线图（boxplot）。2020年8月的气温与相对湿度分别较临时气候正常值（Provisional Climatological Normal, PCN）偏低0.65℃与0.64%；而2021年1月的气温与相对湿度则分别较PCN偏高0.77℃与3.61%。8月的THI值区间为56.25（舒适级）至84.68（紧急级），1月的THI值区间则为74.15（舒适级）至84.07（紧急级）。8月的THI最大值与波动区间均为最大。研究结果表明，乌马伊塔市的奶牛热应激状态已达到警戒级别，即便对于杂交奶牛亦是如此。因此，建议在牧场中设置遮阳设施，以缓解热应激对奶牛生产性能的负面影响。