Comparing Continuous Milking with Sixty-Day Dry Periods in Successive Lactations

Abstract

Five pairs of identical-twin dairy cows were used in a continuous comparison of dry period effects through four lactations. Prior to the second and third parturition one of each pair was milked continuously but the mates were given 60-day dry periods. All twins were given dry periods of 60 days or more before the fourth lactation. Average milk yield of the continuously milked cows in the first lactation was 2.6% above the controls, because they lactated an average of 21 days longer. In the second and third lactation the continuously milked twins produced only 75 and 62% respectively, as much as the controls; and in the fourth lactation they yielded slightly more than the controls. Twins of each pair were fed alike, except that extra grain was fed prepartum only to those milked continuously. This feeding difference resulted in heavier body weights of the continuously milked cows during the second and third lactations, so nutrient reserve difference should have favored the cows milked continuously. The inhibiting effect of continuous milking on the next lactation is more likely due to effects on the mammary gland and its regulating factors than to nutritional factors. © 1965, American Dairy Science Association. All rights reserved.