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 according to a 2 2 factorial design: 2 milking frequencies (1 daily [morning only] milking for the first three weeks of lactation, then 2 daily milkings vs. 2 daily milkings throughout) under two diet energy concentrations (normal or low). The trial lasted 30 weeks, on average, and ended in the pasture on 28 May 2000. During the winter period, the cows were housed together in a free-stall barn, and were given complete rations ad libitum. The cows that were not milked were significantly more vocal than the 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 by cows milked twice a day, with differences of 8.5 kgd -1 (P < 0.01) at week 3. As early as the first week of resumption of twice-daily milking, that difference ceased to be statistically significant but amounted to 1.3 kgd -1 (P > 0.10) throughout the rest of the trial. Once-daily milking did not affect the 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 immunoglobulin 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 weight and body condition losses, and increased the computed energy balance) and had no effect on the ration intake. The normal-energy diet produced expected results, in relation to the low-energy diet: a significant increase in intake (1.2 kg DMd -1 ), milk yield (3.1 kgd -1 ), milk protein content (2.0 gkg -1 ), and nutritional indices, in particular. The decrease in milk yield induced by once-daily milking during the 101