Response of Dairy Cows to Two Systems of Distributing Annual Total Digestible Nutrients Over the Lactation Cycle

Dairy cows fed total digestible nutrients in equal daily amounts (Treatment 1) were compared with cows fed a majority, 60.8%, of their annual total digestible nutrients in the fist 180 days postpartum (Treatment 2).One, two, or three lactations per cow were obtained from a herd of Holsteins and Brown Swiss (Herd 1) and a herd of Jerseys (Herd 2).Average 180-day 4~ fat-corrected milk yields (lactations combined) for Treatments 1 and 2 were 3,-698 and 4,207 kg in Herd 1 and 2,817 and 3,186 kg in Herd 2. The 180-day fatcorrected milk was greater for Treatment 2 in second and third lactations in Herd 2 but did not differ significandy between treatments in first, second, or third lactations in Herd 1 or in the first lactation in Herd 2. Annual (351 days in milk or less) fat-corrected milk yields for Treatments 1 and 2 were 5,516 and 5,806 kg in Herd 1 and 4,385 and 4,604 kg in Herd 2. Milk fat percent essentially was unaffected by treatment.Milk protein percent and, to a lesser extent, solids-not-fat percent were lower for Treatment 1. Annual weight gain was greater for Treatment 1 in the fist lactation in Herd 1 but was not different significantly between treatments in all other groups.Annual fat-corrected milk/total digestible nutrients did not differ significantly between treatments in any lactation in either herd.