The Effects of Parity and air condition on milking performance during a hot summer

Abstract

The effects of parity and environmental temperature on milking performance were investigated during the summer months of 1982,involving 4 primiparous and 4 multiparous dairy lactating cows. The cows were separated into two groups. One group involving 2 primiparous and 2 multiparous cows stayed outside during the entire day except for milking time and 1600h-2030h of sampling periods (Group N). The other group involving 2 primiparous and 2 multiparous cows was air conditioned from 0800h to 2030h and stayed out side from 2030h to 0830h (Group A). The temperature in the air-conditioned barn was controlled at 23±1℃. The results are as follows : 1) The body temperature and respiration rate of Group N paralleled with the change in ambient temperature and increased markedly in early August during which the ambient temperature at 1400h exceeded 30℃. The body temperature and respiration rate of multiparous cows had a tendency to be higher compared with those of primiparous cows in Group N. But those of Croup A were around 38.6℃ and 40 resp./min, respectively. 2) The estimated dry matter intake of Croup A was higher than that of Group N. The estimated dry matter intake per body weight of primiparous cows was not different from that of multiparous cows. 3) The rate of decrease in milk yield of primiparous and multiparous cows in Group N was about 4 and 9 % , respectively, as compared with each yield expected by the normal lactation curve from late June to middle September. Although the rate of decrease in milk yield of Group N was not different from that of Group A for primiparous cows, the former was higher than the latter in the case of multiparous cows. 4) The change in milk fat percent of Group N was different for primiparous and multiparous cows according to the degree of decrease in milk yield. 5) These results suggest that the effect of high temperatures on milk yield was higher in multiparous cows compared with primiparous cows, and that air-conditioning during a hot summer was more effective for the milk yield of multiparous cows. Jpn. J. Livest Management, 28(2) : 62-70. 1992. Received February 28,1992.