Once-a-day milking of multiparous Holstein cows throughout the entire lactation: milk yieldand composition, and nutritional status

摘要

Eighteen multiparous Holstein cows were distributed into two similar groups immediately after calving: the control group (M2) was milked twice a day throughout lactation whereas the other group (Ml) was milked only once a day in the morning. During the indoor (winter) period, all animals received the same total mixed ration ad libitum. In the summer, they were turned to pasture at the same time. The seven cows of group M2 (2 cows were excluded) produced 7323 kg of milk on average in 305 days. The nine cows of group Ml produced 5114 kg of milk (-30%; P < 0.01) over an entire lactation that lasted 12 days less than the twice daily milked cows. Fat and protein concentrations were higher by 3.5 g kg~(-1) (P < 0.01) and 2.1 g kg~(-1 )(P = 0. 06), respectively, in the Ml group. Mean lactose contents (entire lactation) did not differ between groups (P > 0.10) Mean somatic cell count (log_(10) = 5.043 per mL and 4.946 per mL in groups Ml and M2, respectively) did not differ between the groups despite the sharp increase noted in group Ml during the last third of lactation. Casein and whey protein contents also were not significantly different between the groups, Plasmin and lipoprotein lipase activities were unchanged although the plasminogen-derived activity tended to be higher in the milk from group Ml. The dry matter (feed) mean intake amount of the first 14 weeks of lactation did not differ between the two groups although it gradually became higher in the M2 group. Group Ml cows' liveweight and body condition gradually improved over those of group M2, with a difference as high as 56 kg (P < 0.01) and 0.94 point on the body condition score (P = 0.02) on the 36th week of lactation. Eight of the nine Ml cows and four of the seven M2 cows were diagnosedas pregnant. The Ml cows did not show any specific sanitary disorder or abnormal behaviour throughout the lactation.