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

Abstract

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 annual 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 180- day fat-corrected milk for the respective lactations, 3,954, 4,210, and 4,332kg for Treatment 1 and 4,367, 4,312, and 4,169kg 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 6,471kg for Treatment 1 and 6,363, 6,511, and 6,457kg 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 year-end 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 1 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 1 to 180 in all lactations (P<.01, P<.05 and P<.05) and during the total lactation in Lactations 1 and 3 (P<.05).