WHY NOT INTERBULL FOR UK?
UK dairy farmers must still evaluate imported semen using direct conversions while other countries now use Interbull. Why has the Animal Data Centre delayed introduction of what it acknowledges is, in the long term, the best way forward. Sue Rider reports
IMPORTED semen in the UK is still markeked on the basis of converted predicted transmitting ability (PTA) equivalents.
This is despite the fact that most other Holstein-producing countries market sires using international breeding values as calculated by the Interbull Centre in Sweden.
These evaluations combine the bull PTA information from all participating countries to produce an overall ranking of bulls tested in different countries.
In the latest Interbull evaluation of international breeding values 19 countries sent their data to Interbull. The number sending data would seem to confirm that this is recognised as the best way to compare bulls tested in different countries.
Yet the Animal Data Centre has yet to adopt the Interbull evaluations as official for black-and-white cattle in the UK.
ADC geneticist Gordon Swan-son says that while accepting that Interbull is ultimately the way forward, the ADC board is concerned by unexplained anomalies in the rankings (see panel opposite), including the larger than expected reduction in the PINs of many young bulls from the USA.
"It is due, in part, to the general lack of information on daughters and pedigree," he says.
In order to understand this change more fully and ensure the industry receives the best genetic advice, the ADC is asking Interbull and the US to investigate the effect of progeny group size, pedigree information, genetic association between countries, and the caluclation of reliability for individual bulls on evaluations.
"We need to fully understand why these changes have occured in figures from some countries," explains Mr Swanson. "The UK imports about 80% of dairy semen so we must be confident all countries are treated equally."
Most AI companies now accept ADCs reasons for staying with the conversions, but will market bulls mindful of the effect Interbull evaluations will have on the future rankings of bulls.
The unofficial UK Interbull evaluation was unavailable at the time of going to press but will be made available for comparative purposes, according to the ADCs chairman, Bill Madders.
Interbull gives each country bull PTAs on the same scale as normally published in that country. In theory this should enable breeders to select the best bulls from around the world on an objective basis – and the acuracy and reliability of the bull proof should be improved.
Accuracy is said to be improved because daughter and relative details from other countries will contribute to the bulls evaluation in the home country. And reliability of the breeding value or PTA for any particular bull improved because it is based on information from all countries. This means that for a bull jointly tested in two countries, for example, the USA and Holland, both progeny tests will be used to produce a single value. The final PTA will also be influenced by any other information contributed by its relatives.
If everything was the same across countries, for example, the same environment, then the final ranking of bulls would be the same across all countries. But this is not the case and, therefore, there is no single Interbull top 10 or top 100 – with the top bull lists differing in each country.
For example, the tables show the top 10 bulls on Interbull evaluation in the US, Canada, France and Holland ranked on kilos protein.
Dutch sire Etazon Roby, by long-Haven Tradition Perry, is top in the US, Canada and Holland but with a Dutch type score of 97 is not marketed by Holland Genetics. Top bull in France, and Germany, however, is the top French sire Gibbon. *
Animal Data Centre geneticist Gordon Swanson… we need to fully understand why these changes have occured.
Table 1: Top-10 Interbull on French base
De-Su Cubby Checkmate67CubbyUSA
Etazon Labelle BL65Bell Boss BLNL
Skalsumer Kans64Bell GeneNL
Fatal BL64Ugela BLFRA
Norrielake Cleitus Luke64CleitusUSA
Table 3: Top-10 Interbull on US base
De-Su Cubby Checkmate88CubbyUSA
Etazon Labelle BL86Bell Boss BLNL
End-road Leadman Barlo78LeadmanUSA
Skalsumer Kans82Bell GeneNL
Locust-Hill RTL Bristol81LeadmanUSA
Table 2: Top-10 Interbull on Canadian base
Skalsumer Kans93Bell GeneNL
Etazon Labelle BL92Bell Boss BLNL
Fatal BL91Ugela BLFRA
De-Su Cubby Checkmate85CubbyUSA
Delta Luxemburg85Ugela BLNL
Table 4: Top-10 Interbull on Dutch base
Etazon Labelle BL+59Bell Boss BLNL
Skalsumer Kans+57Bell GeneNL
String Milton+54Sunny BoyNL
Norrielake Cleitus Luke+54CleitusUSA
Eastland Cash+53Sunny boyNL
Etazon Lutz BL+53Bell Boss BLNL
WHAT was found when comparing Interbull with conversions?
There was a larger than expected reduction in PINs of US sires. The ADC suggests it is possible that the current US to UK conversion is biased upwards due to the preferential treatment of daughters of high priced semen bulls. Since only a relatively limited number of bulls are included in the official conversion only a few bulls need to be affected to push up the conversion.
A particular problem with young US bulls is that in the Interbull analysis many tend to be regressed back towards their parent average to a greater degree than contemporary bulls from other countries. This is due, in general, to the much smaller initial progeny group sizes of US bulls at 40-50 daughters in comparison with, for example, Holland, where the number is about 80-100 daughters.