In the December Animal Evaluation (AE) run, NZAEL (New Zealand Animal Evaluation Limited) will be implementing two key improvements that will cause some re-ranking of herds, cows and bulls. First, the economic values that are used to calculate Breeding Worth (BW) will be updated, and second, a new fertility EBV (estimated breeding value) will be published.

Breeding Worth (BW) is an index that ranks cows and bulls on their ability to breed profitable and efficient replacement heifers. The BW index is made up of ten different traits, and each trait is assigned an economic value (or weighting) according to its contribution to farm profit. Breeding Worth is calculated by multiplying an animal’s EBVs for each of the ten BW traits by the relevant economic value, and then summing those together.

An Estimated Breeding Value is an estimate of a cow’s genetic merit for a trait.

An Economic Value is an estimate of the value of an extra unit of one of the ten traits of BW when other trait values stay the same. For example: one additional kg of protein creates $5.21 of additional profit for a dairy farmer when all other trait values remain the same.

Economic Values update

Economic values (EVs) are normally updated annually in December to reflect changes in real world costs and revenue.  In 2022, NZAEL decided not to update the EVs for 2023. The update would have resulted in very little re-ranking of animals, but the EVs were likely to be unduly impacted by the high level of inflation occurring at that time. Since then, NZAEL have been working to improve how the economic value model responds to inflation.

In December 2023, the economic values used to calculate BW have been updated to include these inflation-related improvements. At the same time, NZAEL is also undertaking a routine update to key inputs such as the value component ratio (VCR), milk price and cull cow revenue. Most of the re-ranking that will result from the upcoming update is due to an increase in the five-year-rolling average milk price, and a decrease in the VCR (meaning the value of fat relative to protein is decreasing).

Read more about Economic Values.

Trait categorisation Traits (units) Economic value ($/unit change)
Productivity traits Milkfat ($/kg) $4.85
Milk protein ($/kg) $6.83
Milk volume ($/L) -$0.10
Liveweight (($/kg) -$1.59
Robustness traits Functional survival ($/%) $1.88
Somatic cell score ($/SCS) -$46.21
Fertility ($/PR42) $5.77
BCS ($/unit) $164.09
Udder overall1 $0.00
Gestation length ($/day) -$1.89

1 Udder Overall is a nonlinear value. See Economic Values for more information about how this is calculated.

Changes you will see from a new fertility EBV

New Zealand Animal Evaluation Ltd (NZAEL) will introduce a conception-based fertility breeding value (EBV) into the Breeding Worth (BW) index on December 8, 2023. The updated Fertility EBV (pregnancy rate after 42 days of mating; PR42) replaces the current calving rate (calving rate after 42 days of calving; CR42) EBV.

The new PR42 fertility EBV represents the proportion of an animal's progeny that are expected to conceive within the first six weeks of mating. Pregnancy phenotypes (the date that a cow became pregnant) are initially back-calculated by using calving dates to confirm successful matings. In the future we hope to integrate pregnancy test information into this dataset. This will allow us to confirm successful matings soon after pregnancy testing is completed.

On average, the fertility EBVs of bulls will increase by;

  • Jersey bulls (+4%)
  • Jersey cross Holstein-Friesian bulls (+3.5%)
  • Ayrshire bulls (+2.4%)
  • Holstein-Friesian bulls (+0.8%).

The correlation between the current CR42 fertility EBV and the new pregnancy rate (PRR42) EBV is 0.87. This indicates that the current and new EBVs are largely aligned, but some re-ranking among animals is expected in the future.

During this update to the fertility BV, NZAEL will also introduce improvements to how fertility records for embryo transfer donor and recipient cows are handled. This will increase the accuracy of the data feeding into fertility evaluations as animals won’t be penalised for apparent infertility due to unusual records.

Penalties will be introduced for cows culled for fertility and carry-over cows. For example, if a bull has a high proportion of daughters culled for infertility or carried over, his fertility BVs are likely to decrease following the December animal evaluation run.

Testing and validation of the new pregnancy-based EBVs has been undertaken by NZAEL research partners. Based on their results, we are confident that the move to pregnancy-based fertility EBVs will provide farmers with an improved tool for selecting fertile replacement heifers.

Read more about Breeding Values.

Contact NZAEL

For further information or any questions please email: nzael.manager@dairynz.co.nz

Page last updated:

6 Dec 2023