International dairy sires
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6 min read
Selecting the right genetics is key to herd performance in New Zealand’s pasture-based systems. While international bulls offer access to a wider gene pool, their daughters may not perform the same way here as they do overseas. That’s why Interbull data is used to improve the reliability of international breeding values. This provides greater confidence when comparing overseas sires with local ones. This page outlines what to consider when selecting international bulls, how their breeding values are evaluated, and which traits are assessed for New Zealand conditions.
Selecting international dairy sires
To get the best results from our pasture-based systems, New Zealand farmers rely on the right genetics. However, the performance of daughters from international bulls depends heavily on how closely overseas environments and farming systems match ours. This means that strong results overseas don’t always translate to success here. To support better breeding decisions, international data from Interbull adds an extra layer of confidence and improves the reliability of international bulls evaluated for New Zealand conditions.
International bulls aren’t progeny tested here, leading to less data and fewer comparisons. As international bulls sire more daughters in New Zealand, their performance data will be gradually included in Interbull’s breeding values, making them more reliable over time.
When selecting international bulls, prioritise fertility and production efficiency.
Fertility: In New Zealand, poor fertility impacts profitability because our cows calve once-a-year. Overseas, cows often calve year-round, reducing the economic impact of poor fertility. Some international bulls can have lower genetic fertility than New Zealand bred bulls, but many still have daughters with good fertility here.
Production efficiency: The ratio of milksolids to mature liveweight is vital for cow profitability in New Zealand. International bulls often sire daughters with higher mature liveweights, increasing feed costs. These cows need to produce more milk to offset the extra feed required.
Key considerations for selecting international dairy sires
Some international bulls have a limited progeny in New Zealand, which lowers reliability.
Using international bulls can expands your herds genetic diversity.
Traits that perform well overseas might not perform the same in New Zealand.
Check how international bulls compare under New Zealand conditions.
When selecting international bulls, prioritise fertility and production efficiency.
Use a team of bulls to manage risk and maximise genetic gain.
Always ensure international semen meets New Zealand import standards.
To search for international bulls, use the Bull Search, and to see how they are ranked view the Ranking of Active Sires (RAS) list.
How to compare international bulls to local bulls
Interbull, an international bull genetic evaluation organisation, generates breeding values for international dairy sires. They collect international sire data and estimate breeding values for New Zealand based on known relationships between our breeding values and other countries estimated breeding values. NZ Animal Evaluation receives these breeding values three times a year, following each Interbull run, and refines their international sire data to improve consistency and accuracy. This enables reliable global comparisons to give you greater confidence when evaluating international sires against local ones. NZ Animal Evaluation also submits New Zealand bulls to Interbull, giving international farmers the option to select these sires for their own herds.
The benefits of using Interbull for international sire evaluation:
- Enables calculation of breeding values for foreign bulls
- Improves the reliability of breeding values for foreign bulls on national scales
- Provides the ability to compare sires across countries
- Enables comparison of local bulls and imported bulls directly
- Improves national breeding programmes by broadening the available gene pool
Interbull evaluations follow three key steps:
- NZ Animal Evaluation submit bulls’ Breeding Values to Interbull.
- Interbull adjusts the genetic relationships to account for environmental factors.
- The international result is translated into local evaluation to produce a more robust breeding value and its associated reliability.
What traits and breeds are internationally evaluated?
Interbull continues to expand the number of traits it evaluates, with new traits added as international data becomes available and reliable. Although not all breeds and traits are included in Interbull submissions, evaluations are only offered for those that are widely used across multiple countries. For example, the Friesian x Jersey crossbreed is unique to New Zealand and therefore not submitted. As Interbull evolves, you can expect more traits and breeds to be included over time, improving the value of international comparisons.
The following traits are currently included:
Breed Submitted: Holstein, Jersey, Red Dairy Cattle, Brown Swiss, Guernsey
- Volume
- Fat
- Protein
- Direct Survival
- Fertility
Breed Submitted: Holstein, Jersey, Red Dairy Cattle, Brown Swiss
- Somatic Cell
Breed Submitted: Holstein, Jersey, Red Dairy Cattle
- Gestation length – Trait added in 2025
- Milking Speed
- Stature
- Capacity
- Rump Angle
- Rump Width
- Rear Legs
- Front Udder
- Rear Udder
- Front Teat
- Rear Teat
- Udder Overall
Breed Submitted: Holstein, Red Dairy Cattle
- Calving Difficulty (Heifer) - Trait added in 2025
Breed Submitted: Holstein
- Body Condition Score
Dates for international bull evaluation updates
International evaluations are run three times a year. Click below to view the AE run schedule and see when international breeding values are released.
