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“Holstein breeders know that too much emphasis on any one area in breeding can detract from others, so they should continue to select their service sires on the basis of all of the traits important to their business,” he says.
“There are many factors which should influence whether they choose to add the TB Advantage to their breeding criteria,” he
continues. “These are likely to include whether their herd is within or close to a bTB affected area or whether they feel that having progeny by a bull with a better TB Advantage will give them some commercial benefit, such as when selling livestock.” However, he says that if all other traits are equal, it would definitely be preferable to use a bull with a positive TB
Which animals will have a TB Advantage?
Only Holsteins will initially have a TB Advantage because there’s considerably more data available for the Holstein than for any other breed. The index will be calculated for bulls which either have daughters milking in the UK (daughter-proven bulls) or have had their genotype measured (genomic bulls). In effect, this means there will only be a few commercially available Holstein bulls which don’t have a figure calculated for TB Advantage. However, breeders should note that some bulls which have obtained their progeny indices outside the UK will have a larger genomic contribution to their TB Advantage than for other components of their genetic index due to the lack of bTB information from international sources. Longer term, this information may be available from countries such as Ireland. Any breeder obtaining a genomic index for females in their herd will also now obtain a score for TB Advantage.
How reliable is the TB Advantage?
Genetic indices are published with a reliability figure which gives an indication of how likely the index is to change as more information is added. The reliability for the TB Advantage ranges from 20% to 99%, with an average reliability of 65% for bulls with UK daughters and 45% for those with a genomic index only. Although the reliability of genomic predictions for the TB Advantage is currently less than for some other indexes, it can still be used a part of a herd’s breeding strategy and has shown to be valuable in predicting future performance.
When and where is the TB Advantage published?
The TB Advantage is published by AHDB Dairy as part of the routine dairy cattle genetic evaluations service. Indices are published three times a year in April, August and December. They are always available on the AHDB Dairy website at:
dairy.ahdb.org.uk
Holstein UK and CIS offer a full range of genomic tests.
Advantage and that using bulls with an extremely negative TB Advantage is inadvisable as it is likely to increase the susceptibility of a herd to bTB. “Like all genetic improvement, this is a step-by-step approach, but by taking those steps in the right direction, you are undoubtedly helping to stack the odds in your favour,” he says.
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