The Council for Dairy Cattle Breeding released a new trait this week, Gestation Length (GL), that will allow dairy farmers to more accurately pinpoint the time of calving.

For example, females bred to a Holstein bull with a GL Predicted Transmitting Ability (PTA) of +4 days are expected to carry their calves about 281 days, or four days longer than the breed average of 277 days. A Holstein bull with a GL PTA of -5 would be expected to have mates carry calves just 272 days, on average.

According to CDCB, the new trait offers three benefits:

  • For grazing herds or seasonal herds, it will allow farmers to more tightly concentrate calvings.
  • In all operations, farmers should be better able to time dry dates, pinpoint expected calving dates and better manager maternity pen usage and flow.
  • The new traits will also allow researchers to better understand other traits such as calving ease, stillbirths and age at first calving.

GL PTA will be available for all six breeds and even crossbred animals if parentage of the crossbred female is known.

There is breed variation in gestation length. Below is the average gestation length by breed for the base year (2010).

  • Ayrshire: 281
  • Brown Swiss: 286
  • Guernsey: 284
  • Holstein: 277
  • Jersey: 278
  • Milking Shorthorn: 279

Read more on GL PTA here