New group of dairy bulls

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Australian dairy farmers now have access to a new category of bulls, with the inclusion of genomically-tested bulls in the April release of Australian Breeding Values (ABVs) by the Australian Dairy Herd Improvement Scheme (ADHIS).

Until now, dairy farmers using artificial insemination (AI) have had the choice of using progeny test or proven bulls or both.

Progeny test bulls are young bulls whose straws are marketed by breeding companies at lower prices to dairy farmers who herd record. Production and other performance data is collected from the daughters of these joinings. When enough data is available to calculate a reliable ABV, the bull is considered proven 

Progeny test bulls represent newer genetics so should have higher genetic potential, but without daughter data, they are ‘unknown' and daughter performance is unpredictable.

While proven bulls are more reliable they are also older, as it takes a number of years to collect the performance data needed to calculate an ABV, which is a prediction of its commercial performance.

Genomics is the use of DNA data, (or gene markers) to help in the calculation of breeding values. Genomic testing - or genotyping - can done on an animal at any age, allowing breeding values to be estimated for young bulls, long before they have daughters in production. In Australia it is expressed as an ABV(g).

Genomics will fast track genetic gain, by allowing dairy farmers to use young bulls with greater confidence.

When purchasing bulls to use over their herd, Australian dairy farmers can now include progeny test, genomically tested and proven bulls in their bull team.

Daniel Abernethy from the ADHIS said the April release of ABVs includes the first ABV(g)s for young bulls that have been genomically-tested.

"This is a very exciting development. Dairy farmers now have more choice, in terms of genetic potential and reliability when selecting bulls to use over their herd."

ABV(g)s are directly comparable to ABVs, enabling farmers to easily compare bulls, whether they are proven or genomically tested.

"When using genomically-tested bulls, we recommend using a team of several bulls to spread risk. Remember, bulls with an ABV(g) are not yet proven so their reliability is less than proven bulls," said Mr Abernethy. For every proven bull that is replaced, make sure you use at least two bulls with an ABV(g) and make sure at least half the doses are from proven bulls from the Good Bulls Guide."

Mr Abernethy said ABV(g)s are the best estimate of a young bull's performance in Australia because the evaluation draws on performance data from the Australian herd.

"The calculation is based upon results from genomic testing and pedigree data and linked to a strong reference population of animals whose performance is well known in Australia."

The ADHIS uses world's best practice and has no commercial association.

The April release of ABVs will occur on Monday 11 April 7am, from the ADHIS website. The release includes ABV(g)s and ABVs for a new trait, called Rear Teat Placement. Summaries of the results can also be found in the April 2011 edition of the Good Bulls Guide which will be published by ADHIS on the web 11 April and in print early May.