Relation of Days Open and Days Dry to Lactation Milk and Fat Yields

The relationships between days open, days d~T, and 90-day and 305-day production were studied, using 4,385 lactation records from nine North Carolina Institutional Holstein herds from June, 1950, through December, 1958. Relationships were studied separately for first, second or later, and all lactations to determine if adjustment of 305-day lactation records for days open snd days dry are warranted in compiling sire summaries.