How long does a cow need to be dry? Everyone has a slightly different idea. Most people agree that a cow should have a dry period between 40 and 60 days. Research consistently shows that second lactation cows will produce more milk and have lower cell counts with a 55-to-60-day dry period. Older cows with longer calving intervals can maintain productivity with shorter dry periods. Too long can be as bad as too short. Long or short dry periods may result in more days open in some herds. Analyzing your own records can help you determine what is best for your cows on your dairy.
But the question is, how long was she dry? According to the Dairy Records Management System (DRMS) database the average herd has 4% of dry periods shorter than 40 days and 8% of dry periods longer than 70 days. That is a tight window. At 4%, early calvings can account for most of the short dry periods. But the extreme herd in the DRMS database had 54% of dry periods less than 40 days. How does that happen? How many long and short dry periods do you have in your herd?
Is the gestation length set correctly in your herd management software? 283 days is a common default gestation length in herd management software. 274 is a much more common gestation period with modern Holstein genetics. Your program can tell you the actual value for your farm. Think about that difference. Even if the dry off list is followed perfectly, the default setting means the average cow is dried off 9 days late. Even if you use Dairy Comp or PC Dart to generate your dry cow list, the gestation setting in Horizon or DelPro is determining when cows move to the late lactation feed table and late lactation milking permission. Sometimes those don’t start until 10 days before dry off.
How often do you dry cows off? Some farms dry cows off one at a time, when they reach the target date. It is more common to dry off batches of cows every week or even every other week. If your target is 45 days dry, and you dry cows off every other week, you need all the cows that are less than 59 days to calving. If you skip a week for a holiday or field work, it goes to 66 days. Again, the length of the dry period isn’t the only thing affected. Late lactation feed tables and late lactation milking permission need to be adjusted to account for the dry off schedule on the farm.
How long does she need to be in the prefresh pen? If your transition program includes anionic salts or zeolite for prevention of milk fever, the time in the prefresh pen is critical. Too short and the product doesn’t have time to work – too long and it is overfed. The gestation length in your herd management software also controls the time in the prefresh pen.
Don’t rely on the default gestation setting in your herd management software. I can help you determine the actual gestation length for your farm and make appropriate adjustments. Then we can make sure your management lists match the management practices out in the barn. Finally, we can check the late lactation feed tables and milking permission to make sure they are right for your cows and your management practices. Getting the dry period right is reason enough. But so much more depends on it.
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