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An article by Simon-Pierre Loiselle, T.P.
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Two clients were concerned about whether the average gestation period of their Holstein herd was normal at 276 and 277 days respectively.
A recent study showed that these gestation periods are well within the expected average. In herds with shorter gestation periods (10 days less than average), the heifers would probably be underweight (due to lack of space for the calf). Other factors, such as stress (excessive heat and/or cold), selection for calving ease and the use of sexed semen also tend to reduce the gestation period.

A study from 1932 (by J.C. Knott) found an average gestation period of 280 days and reported that the highest producers at the time had a gestation period that was 1 to 2 days shorter than average. Female calves and twins had a gestation period that was 1 to 1.5 days shorter. It would seem that gestation periods have shortened over the years and adjustments should be made. Considering that first lactation requires at least a 60-day dry period, it would be logical to aim to begin drying-off at 215 days of gestation.
Therefore, if you use a breeding wheel and you want to make sure your first calvers have a minimum of 60 days of rest, you have to begin drying-off seven days earlier than indicated by the arrow on the wheel!

As in the rest of our industry, everything is evolving and thanks to farm data management software, you can now get up-to-date information on what is happening on your farm. Take the time to check and make the necessary changes in order to give your cows the correct rest period.