The 2020 Genetic Evaluations seen a lot of change for farmers. One such change was to the calving evaluations.


As part of the January 2020 genetic evaluation, there has been a significant update to how calving difficulty is displayed. Until now, each bull had a single Calving Difficulty PTA (and reliability). This provided an indication of the expected incidence of calving difficulty, irrespective of the type of female that bull was mated with (i.e., heifer or cow).


In January, the board of ICBF approved the implementation of changes to the calving difficulty evaluation, in this proof run. With the new update, the calving difficulty PTA % will be split into two: Dairy Heifer Calving Difficulty PTA % and Dairy Cow Calving Difficulty PTA %. These will reflect the truer incidence of on-farm calving difficulty.

This is a considerable change to how we as an industry have understood the calving difficulty figures. Until now, farmers considered bulls with a calving difficulty PTA of less than around 2.4% and a high reliability as ‘safe’ on heifers; this will no longer be considered best practice. From herein, the advice from ICBF is to use the calving difficulty figures relevant to the type of female to be bred. (i.e., heifer or cow)


When selecting bulls for use on cows, use the dairy cow calving difficulty PTA (and associated reliability). When selecting bulls for use on heifers, use the dairy heifer calving difficulty PTA (and associated reliability).

To help with the change-over to this new method of displaying calving difficulty, we have developed a ready reckoner that will aid farmers in the transition from the single calving difficulty PTA to the two new traits: Dairy Heifer Calving Difficulty PTA % and Dairy Cow Calving Difficulty PTA %. ICBF will be posting a ready reckoner and further information to all HerdPlus farmers over the coming weeks.


The Animal Search, Active Bull Lists and Stock Bull Finder have all been updated with the new calving evaluation data. Reports (EBI, Euro-Star, BDGP Eligibility, etc.) will be updated over the coming weeks. Farmers will be notified by text as soon as these reports are available online.

Ready Reckoner explained:

The purpose of the Ready Reckoner is to help farmers to visualise the change from one single calving difficulty PTA to two and how this varies between heifers and cows.

For example: If previously you were selecting a Hereford bull to use on your dairy heifers with a calving difficulty of 1.8%, this figure will now display (on average) as 9.2% for dairy heifers and 3.8% for dairy cows. This more accurately represents the incidents of calving difficulty on the ground.

Old Calving Difficulty Range Breed Dairy Heifer Dairy Cow
0.1% to 2.4% HE 9.2 3.8
2.5% to 3.4% HE 10.4 4.5
3.5% to 4.4% HE 11.8 5.1
4.5% to 6.0% HE 13.9 5.8
6.1% to 7.3% HE 16.3 6.6
>=7.4% HE 19 7.4

Calving Difficulty Ready Reckoner Dairy

Click to view figures for all breeds

Calving Difficulty Ready Reckoner Beef

Click to view figures for all breeds


For more information, please view the ‘New calving evaluations’ presentation from the recent ICBF & Sheep Ireland Genetics Conference.