Gestation Length EBVs provide an estimate of genetic differences between the period from the date of conception (i.e. when the female gets in calf) to when the subsequent calf is born. Shorter gestation length is generally associated with lighter birth weight, improved calving ease and improved re-breeding performance among dams. In addition, calves born with a shorter gestation length may be heavier at weaning due to more days of growth.

How do I record Gestation Length Information?

Gestation Length EBVs are calculated from both the joining date and date of birth records for calves conceived by either AI or Hand Mating.

The information that needs to be recorded for the calculation of Gestation Length EBVs includes:

• the date of birth details for each calf
• the joining (or AI) date of any AI or Hand Mating joinings

Importantly, you do not need to calculate the gestation length for each calf. BREEDPLAN will calculate this from the information specified above.

What considerations should be made when recording Gestation Length Information?

• No information from natural matings is used in the calculation of Gestation Length EBVs. Although some natural matings may be observed, they are not currently used in the calculation of gestation length as there is no guarantee that the observed mating is the one that successfully results in the conception of the calf.
• Gestation length information is currently excluded from the BREEDPLAN analysis if (a) the calf is an embryo transfer calf, (b) the calf is a twin, (c) only one animal is represented in a contemporary group, or (d) more than 2/3 of animals in a contemporary group have the same gestation length.

How do I submit Gestation Length Information?

Gestation length information can be submitted to your breed society when submitting your calf registration details. Please contact staff at your breed society should you have any queries about how to submit this information.

For more information regarding how to record gestation length or Gestation Length EBVs in general, please contact staff at your BREEDPLAN processing centre.