Response of Dairy Cows to Two Systems of Distributing Annual Concentrates Over the Lactation Cycle

Dairy cows fed a majority of their annual concentrate during early lactation were compared to cows fed approximately equivalent amounts distributed evenly throughout the year.Forage was ad libitum for both treatments.Percentages of an~ nual concentrates consumed during days 1 to 180 postpartum of first, second, and third experimental lactations were 49.4,49.5, and 49.4 for Treatment 1 and 73.8, 66.9, and 66.6 for Treatment 2. The 180day fat-corrected milk for the respective lactations, 3,954, 4,210, and 4,332 kg for Treatment 1 and 4,367, 4,312, and 4,169 kg for Treatment 2, was different between treatments (P < .01)only in first lactation.Total lactation fat-corrected milk for the respective lactations, 6,122, 6,392, and 6,471 kg for Treatment 1 and 6,363, 6,511, and 6,457 kg for Treatment 2 was not different between treatments in any lactation.Weight loss during early lactation was slightly larger (P > .05)for Treatment 1 in all three lactations, and yearend body condition did not differ between treatments (P > .05).Average milk fat per cent did not differ between treatments in any lactation either during Days I to 180 or the total lactation.Average milk protein per cent was lower for treatment 1 for Days 1 to 180 postpartum (P < .01)and for the total lactation (P < 0.05) in the first and second lactations.Average per cent solids-not-fat was lower for Treatment 1 during Days I to 180 in all lactations (P < 21, P < .05 and P < .05)and during the total lactation in Lactations I and 3 (P < .05).