热应激对不同生长阶段荷斯坦奶牛异常行为的影响

Abnormal Behavior of Holstein Cattle at Different Growth Stages under Heat Stress

为探究热应激下荷斯坦奶牛异常行为发生率,本研究调查了夏季北方地区5家规模化养牛场的断奶犊牛、后备牛、泌乳牛3个生长阶段共2152头奶牛的异常行为发生情况,记录每天各牛群08:00—17:00的温热环境和异常行为参数,每家牛场观测3 d。结果表明:牛群总体样本异常行为发生率为18%~25%,异常行为发生率随温湿指数(THI)升高而显著减低,同一THI区间下异常行为发生率为断奶犊牛>后备牛>泌乳牛;泌乳牛和后备牛的异常口部行为随THI增加显著降低,断奶犊牛在THI低于89的环境中,异常口部行为发生率随THI增加显著增加,在THI高于89时显著降低;奶牛异常交互行为和异常体况行为发生率随奶牛生长而极显著减低,但不受THI变化影响;泌乳牛和后备牛的异常交互行为发生率低于2%,断奶犊牛发生率为4%~7%;后备牛异常体况行为发生率低于9%,断奶犊牛发生率为8%~12%。综上可知,热应激水平增加会降低奶牛异常行为的发生,且对泌乳牛和后备牛的影响大于断奶犊牛,异常行为发生率为断奶犊牛>后备牛>泌乳牛,呈现显著降低态势。

In order to investigate the incidence of abnormal behavior of Holstein dairy cows under heat stress,this study investigated the abnormal behavior of 2152 cows in 3 growth stages of weaning calves,replacement cows and lactating cows from 5 large-scale dairy farms in northern China in summer.Animals’performing abnormal behavior was recorded hourly from 8:00 to 17:00 in three consecutive days.The temperature and humidity of the environment were recorded at the beginning of each observational hour.The results showed that the incidence of abnormal behaviors in the overall observational herd was 18%~25%,and it decreased significantly with increasing THI.The incidence of abnormal behavior in the same THI interval decreased with increasing growth stage;The abnormal oral behavior of lactating and replacement cattle decreased significantly with the increase of THI.The incidence of abnormal oral behavior increased significantly with the increase of THI in weaned calves below the THI range of 89,and when THI is higher than 89,the incidence is significantly reduced;The incidence of abnormal interaction behaviors and abnormal body behaviors of dairy cows were not affected by THI changes;The incidence of abnormal interaction behavior in lactating and replacement cattle was less than 2%,and the incidence of weaned calves was about 4~7%.The incidence of abnormal body behavior of replacement cattle was less than 9%,and the incidence of weaned calves was 8%~12%.In conclusion,cattle under heat stress performed less abnormal behavior,and this reduction effect was more pronounced in lactating and replacement cattle compared with weaned calves.In addition,the abnormal behavior incidence decreased with the increasing growth stage.