山西省夏季奶牛热应激程度及奶损失调查

Investigation of heat stress degree in dairy cattle and milk losses in summer in Shanxi province

为了研究我国北方夏季奶牛处于热应激的程度及热应激导致奶损失的情况,试验采用实测2013年7月中旬山西省三个规模化牛场各一栋代表性牛舍的四个位置早、中、晚的温度、湿度和收集牛场2013年DHI数据与牛场所在或周边城市气象信息,利用固定模型分析了牛舍不同时间段、不同位置的温湿度指数(THI)的差异,并粗略估计牛群夏季热应激奶损失的情况。结果表明:牛舍THI在中午(11:00—13:00)和晚上(18:00—20:00)时间段显著高于早晨(06:00—07:00),且多数时间段THI超过72,部分时间段THI超过76;在多数时间内,牛舍中间位置THI高于两边位置,且在中午时间段THI大多超过72;当地7,8月份THI接近或超过72时,群体测定日平均产奶量开始降低,即THI每升高1个单位,群体平均日产奶量约下降0.39 kg以上,且产奶量降低趋势有延迟到9月份的现象。说明夏季山西奶牛确实受到轻度热应激影响,养殖中尤其应针对牛舍重点位置在重点时间段加强防暑降温措施,减少因热应激带来的奶损失。

To study the situation of the heat stress degree in dairy cattle and milk losses caused by heat stress in summer in northern China, tem- perature and humidity data were measured at 4 positions in each of the representative barns from three scaled dairy farms in Shanxi province three times per day （ morning, noon, and evening） in the middle of July,2013. The DHI data of the researched dairy farm in 2013 and meteoro- logical information of the city （ which the farm was located or nearby） were collected. The differences in the temperature - humidity index （THI） at different time periods and positions were analyzed using a fixed model, and the milk losses caused by heat stress in summer were roughly estimated. The results showed that THI of the barn at the noon time （ 11：00--13：00） and evening time （ 18：00--20：00） ,was signifi- cantly higher than that at the morning time period （06：00---07：00） ,and the THI at most of the time periods exceeded 72 ,and THI at part of the time periods exceeded 76; in most of time periods, the Till in the middle position was higher than that at the sides, and most of the THI at noon exceeded 72 ; when the THI was dosed to or exceeded 72 in the local in July and August, the average daily milk yield determined in the herd, started to decline,it showed that the average daily milk yield decreased at 0.39 kg and more with per unit increase in THI, and there was a phe- nomenon that the decreasing trend of milk yield extended to September in 2013. The results indicate that dairy cattle undergo mild heat stress during summer in Shanxi province. Therefore,summer cooling measures should be strengthened especially at the key positions and during key time periods for the barn to reduce the milk losses caused by heat stress