Combined effects of once-daily milking and feeding level in the first three weeks of lactation on milk production and enzyme activities, and nutritional status, in Holstein cows

Twenty-four multiparous cows were divided into 4 groups immediately after calving ac-cording to a 2 × 2 factorial design: 2 milking frequencies (1 daily [morning only] milking for the firstthree weeks of lactation, then 2 daily milkings vs. 2 daily milkings throughout) under two diet energyconcentrations (normal or low). The trial lasted 30 weeks, on average, and ended in the pasture on28 May 2000. During the winter period, the cows were housed together in a free-stall barn, and weregiven complete rations ad libitum. The cows that were not milked were significantly more vocal thanthe controls, close to the omitted milking, and in a large number of them, milk leaked from the udder.Once-daily milking gradually reduced the amount of milk secreted in relation to that produced bycows milked twice a day, with differences of 8.5 kg·d–1 (P < 0.01) at week 3. As early as the first weekof resumption of twice-daily milking, that difference ceased to be statistically significant butamounted to 1.3 kg·d–1 (P > 0.10) throughout the rest of the trial. Once-daily milking did not affectthe contents of milk fat, true protein, serum albumin and lactose contents or somatic cell count,plasmin activity and plasminogen-derived activity. That treatment also increased the G1 immuno-globulin concentration (P = 0.02; measured at week 3) and reduced milk lipoprotein lipase activity.Once-daily milking improved the nutritional status at the beginning of lactation (reduced live weightand body condition losses, and increased the computed energy balance) and had no effect on the rationintake. The normal- energy diet produced expected results, in relation to the low-energy diet: a signifi-cant increase in intake (1.2 kg DM·d–1), milk yield (3.1 kg·d –1), milk protein content (2.0 g·kg –1), andnutritional indices, in particular. The decrease in milk yield induced by once-daily milking during the first three weeks of lactation was 5.5 kg·d –1 in the low-energy group and 8.5 kg·d –1 for the normal en-ergy group (non- significant interaction; P > 0.10)