Interbull have an animal evaluation system which collates cow breeding values from all around the world. The relevance of how a bull’s daughters are performing overseas depends on how similar the environment and farming systems are between NZ, and the home country of each daughter.
Most dairy farms in New Zealand are predominately pasture based, and almost all NZ dairy cows graze pasture every day of the year. This makes our farming conditions somewhat unique, which means genetics that work overseas do not necessarily work well here.
Interbull account for the relationship between NZ and other countries, and then use daughter information from around the world as best they can to create NZ specific breeding values.
These breeding values are received by NZAEL after each Interbull AE run (three times each year).
Because of the differences between NZ and other countries, Interbull breeding values on the NZ scale often have low accuracy. As a bull accumulates daughters in NZ, the performance information will be gradually blended with Interbull breeding values, until the international data is disregarded and the BVs are based entirely on the performance of a bull’s NZ born daughters.
Why are BWs for international bulls less accurate?
- NZ farming conditions are very different to the rest of the world.
This means that daughter performance overseas is not a good indicator of how a bull’s daughters will perform in NZ
- NZ performance data is often limited.
International bulls are not progeny tested in NZ, which means that there is less data collected, and they are compared against fewer bulls.
Why are BWs for international bulls typically low?
In NZ, poor fertility in dairy cows has a very big impact on profitability. Overseas the economic impact is substantially less, as cows are often calving year around. For this reason, international bulls often have lower genetic fertility when compared to NZ bred bulls.
- Production efficiency
The ratio of milk solids to mature liveweight is a key driver of cow profitability in NZ. Internationally bred bulls tend to produce daughters who have a higher mature liveweight. This creates cost for a farmer, as that animal requires more feed to be reared, and more feed for maintenance once fully grown. High liveweight cows must produce additional milk to justify the cost that their liveweight incurs, if they are unable to do so, a penalty will come through in their BW.