Dry Period to Maximize Milk Production Over Two Consecutive Lactations

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Abstract
Dry period to maximize daily milk spanning 2 lactations depended on age, calving interval and daily milk on the 100th day before calving which followed the dry period. The study was on Dairy Herd Improvement records made 1975-1977 by 8981 Holstein cows in Ohio (USA). Dry period accounted for more variation of daily milk produced after the dry period (2.4%) than of daily milk produced during the calving interval including the dry period (1.1%). Days dry to maximize daily milk was most affected, in order, by age at calving in the lactation preceding dry period, calving interval spanning dry period and daily milk on 100th day before calving. Optimal number of days dry declined from 65 to 23 days as age at calving increased from 24 to 83 mo. Cows with calving intervals < 340 days required at least 55 days dry. Cows following 1st lactation required 44-70 days dry, depending on age, calving interval or 100th day milk. Twelve to 17 more days dry helped daily milk as 100th-day milk increased from 12.7 to 19.3 kg for 1st lactations. Economic benefits of maximizing days in lactation depend on production in late lactation necessary to cover costs of daily feed and labor.