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item Kuhn, Melvin
item Hutchison, Jana
item Norman, H

Submitted to: Animal Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2005
Publication Date: 11/14/2005
Citation: Kuhn, M.T., Hutchison, J.L., Norman, H.D. 2005. Minimum days dry to maximize milk yield in subsequent lactation. Animal Research. 54:351-367.

Interpretive Summary: Identifying the minimum dry period length (the period between lactations when a cow is not being milked) needed to maximize milk yield in the subsequent lactation was the objective in this study. A dry period length of 60 to 65 d maximizes subsequent lactational milk yield. This research is useful on a farm level to dairy producers trying to determine how many days before calving a cow should be dried off.

Technical Abstract: The objective of this research was to determine the effect of days dry (DD) on actual milk yield and to identify the minimum dry period length needed to maximize milk yield in the subsequent lactation. Field data collected through DHI from January, 1997 to December, 2003 and extracted from the Animal Improvement Programs Laboratory national database were used for analysis. Actual lactation records calculated from test-day yields using the test-interval method were used in this study. The model for analysis included herd-year of calving, year-state-month of calving, previous lactation milk yield, age at calving, and days dry as a categorical variable. Interactions were added to this model to determine if the effects of DD on subsequent lactation milk yield depended on previous lactation milk yield, age at calving, SCS, or DO. Milk yield in the subsequent lactations was generally maximized with a 60 to 65-d dry period, regardless of parity. DD effects on milk yield were, for the most part, consistent across lactations, although short dry periods after first lactation are somewhat more detrimental to milk yield than short DD after second and later lactations. Dry periods less than 20 d results in very pronounced losses in subsequent lactation yield. A short dry period for high producing cows that bred back early in lactation proved to be the worst combination in terms of maximizing subsequent lactation milk yield.