21 July 1995

Changes now promise more accurate proofs

TWO changes to the evaluation system for UK dairy proofs should guarantee the improved accuracy of future figures.

Animal Data Centre geneticist Gordon Swanson says he is confident he will now have access to enough test day records to enable records-in-progress to give an accurate 305-day prediction.

The second improvement recognises that imported daughters of foreign bulls may be treated differently from home-bred daughters in certain herds.

When this happens it could affect the bull rankings, says Mr Swanson. This was illustrated when he removed the 1600 imported daughters in the UK from the evaluation run. PTAs of some bulls changed significantly.

Such a record loss would be impractical. To overcome this, the ADC will now batch all imported daughters within a herd and compare like with like. Home-bred daughters within a herd will be compared only with other home-bred daughters and not with a group that includes imported animals.

The result has seen a change in the UK PTAs of a few high profile bulls, says Mr Swanson.

For example, based on Jan 1995 figures, the US sire Blackstar sees his UK proof drop 137kg milk, 3kg fat and 4kg protein. Sunny Boys UK proof goes up 42kg milk 0.5kg fat and 1.1kg protein.

Mr Swanson says the changes for Blackstar and other US bulls bring their UK proof more in-line with their converted proof. Sunny Boy still remains below his converted figures which could be due to his daughters flat lactation curves and the fact that his UK proof is 40% records in progress.

Another reason for his below average performance is that his imported daughters are very average compared with imported contemporaries-whereas his UK daughters are performing well compared with contemporaries. Mr Swanson explains that as more UK-bred daughters contribute to Sunny Boys evaluation, the effect of his imported daughters will decrease.

&#8226 Changes will be introduced in the July UK evaluation run (see Livestock, Aug 4).