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
Résumé
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 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 kg·d–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 kg·d–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 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 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 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), and
nutritional 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)