The Study On Effects Of Seasons On Body Temperature And Activity Of Holstein Cows, And The Rules Of Returning Estrus After Cows Breeding

Summer heat stress has led to a serious reduction in dairy cows production performance,thus increasing the stress of feeding and reproduction management.Although the temperature and humidity index(THI)is an important environmental index and can help to infer the degree of heat stress,it does not reflect the physiological changes and health status experienced by dairy cows undergoing heat stress.However,the body temperature is an important physiological parameter in the evaluation of the health state of dairy cows.Therefore,the body temperature and activity of dairy cows were monitored by using the estrus monitoring system developed by our team and the changes of body temperature during heat stress and non-heat stress were explored,and it is expected to monitor heat stress through physiological indicators and environmental index,so as to reduce the adverse effects of heat stress.In addition,cows are prone to returning estrus after artificial insemination,so revealing the activity changes of return estrus cows can provide theoretical guidance for breeding and reproductive management of dairy cows,as well as monitoring of dairy cows with estrus.For improving the technology for rearing dairy cows,the vaginal temperature(VT)and walking activity of young Holstein cows in summer(n = 20),autumn(n = 20),and winter(n = 20)were measured using the estrus monitoring system developed by our team.The effects of ambient temperature and humidity on diurnal body temperature and walking activity were investigated,and heat stress monitoring was explored.We found that VT fluctuated slightly at approximately 38.3°C when the ambient temperature was < 20°C or temperature-humidity index(THI)was lower than 68.However,when the ambient conditions were above this range,VT increased significantly with increasing ambient temperature and THI(P<0.001),while walking activity decreased significantly(P<0.001).Moreover,in summer,the relative increase in VT and activity during estrus differed significantly from those in autumn and winter(P<0.05).In addition,from 02:01 to 07:00 h,activity of cows during summer did not significantly differ from that in autumn and winter(P>0.05),and the average body temperature of the cows was 38.4°C,which suggested that heat stress might be alleviated during this period.Therefore,the combined monitoring of body temperature and THI might provide accurate guidance for preventing and controlling heat stress.Pregnancy diagnosis is an important part for the management of cow's reproduction,and revealing the rules of return estrous cows after artificial insemination is a basis of better guidance for the management of cow's feeding and reproduction.Therefore,our team collected the data of returning estrus and activity of 214 multiparous cows after artificial insemination in a dairy farm.Statistical analysis found that the proportion of return estrous cows in the first,second,third and fourth estrous cycle after artificial insemination was 48.7%,29.9%,16.2%,5.1%,respectively.The activity before and during returning estrus showed a downtrend with the increase of parity,time of returning estrus as a whole.Simultaneously,the duration of returning estrus also gradually decreased with the prolongation of pregnancy,and the activity of cows in return is significantly decreased in summer(P<0.05).The management of cow's reproduction should be paid more attention during the first and second estrous cycle after artificial insemination,and the feeding management and pregnancy diagnosis should be strengthened.At the same time,considering the effects of above factors on activity,the automatic monitoring of return estrous cows can be carried out scientifically by using activity parameter.In addition,it is necessary to explore the mechanism of cow's pregnancy for us to improve the pregnant effect of cows.