DairyNZ subsidiary New Zealand Animal Evaluation (NZAEL) will update the genetic base used to calculate Breeding Worth (BW) on 20 June 2025. This routine update will cause a drop of approximately $185 in BW across all cows, bulls, and herds but does not reflect any loss in genetic value or animal performance.
To assist with ranking within a population, it’s helpful to have a benchmark. In animal evaluation, this reference point is called ‘Base Cow’. A Base Cow change causes very minimal re-ranking among bulls, cows, herds or breeds. It simply shifts animals up or down depending on the genetic base that is chosen. Base Cow creates a yard stick to measure how much genetic progress is being made with each passing generation.
“New Zealand’s dairy herd continues to make meaningful genetic improvement. Each generation of heifers enters the herd with higher BW on average, than the previous generation, leading to higher protein, fat and greater efficiency. Updating the Base Cow ensures BW remains an important and accurate ranking tool, reflecting the performance of today’s dairy animals,” says Andrew Fear, NZAEL Manager.
From 20 June, the BW of the average dairy animal will move from $241 to $56. This shift follows the introduction of an updated reference point, known as a Base Cow, which will now be based on 2015-born animals instead of the current 2005 cohort.
“Farmers should expect to see a drop in BW figures when accessing herd records after 20 June,” says Andrew Fear. “However, it’s important to remember that the relative ranking of animals will remain largely unchanged, and the actual genetic merit or production potential of animals has not diminished.”
The update has caused very little change in the rankings of cows, bulls, or herds. One trait; Udder Overall will impact BW differently after the base change due to the way it is incorporated in BW. However, the overall rankings remain highly consistent, with a greater than 99% correlation to previous positions.
When making breeding decisions or benchmarking animals, farmers are encouraged to:
- Check the date of herd data to ensure a fair comparison
- Understand that a lower BW number reflects the new Base Cow, not a reduction in animal quality
- Focus on relative rankings between animals and long-term performance trends
From 2025, the genetic base will be updated every five years, in line with international standards, to ensure BW continues to reflect genetic progress. The next updates are planned for:
- 2030 – referencing 2020-born animals
- 2035 – referencing 2025-born animals
Further information about the BW update, including a detailed breakdown of the genetic base cows and changes to Breeding Values, is available here.
Media contact
Jacob Quinn
Principal Corporate Communications Advisor
p: 027 716 4197
e: jacob.quinn@dairynz.co.nz
