2016-01-22   facebooktwitterrss

First Ever TB Index Published

A brand new genetic index for Holstein bulls – the TB Advantage – has been published by AHDB Dairy.

The index represents the culmination of months of research using hundreds of thousands of cow records, and will help dairy farmers breed improved resistance to bovine tuberculosis (bTB) into their herds.

Table 2

Top 20 daughter-proven bulls ranked on Profitable Lifetime Index (£PLI) showing new TB Advantage (January 2016)

Table 2

Top 20 young genomic bulls ranked on Profitable Lifetime Index (£PLI) showing new TB Advantage (January 2016)

Expressed on a scale which typically runs from -3 to +3, many of the highest Profitable Lifetime Index (PLI) bulls also have a good positive score for TB Advantage (see tables).

“PLI has been a national breeding goal for UK dairy farmers for a number of years and the high scoring PLI bulls have generally come through with very good indexes for TB Advantage,” says Marco Winters, head of genetics for AHDB Dairy. “This is both reassuring – in that it indicates cattle breeding is already heading in the right direction – and unsurprising, since health and fitness traits represent an important component of PLI.”

In fact, health and fitness represent around 68 per cent of PLI, and analysis has shown there’s a favourable correlation between the TB Advantage and general health and fitness.

Furthermore, Mr Winters remarks that the youngest sires with the most modern genetics, on average have the highest TB Advantage, with scores ranging from -2.2 to +3.3 for the actively marketed group.

“This is another positive trend and a further demonstration that progress in breeding is being made,” he says.

In fact, from a complete dataset of bulls whose average TB Advantage is zero, only the best bulls are marketed to UK farmers, which explains why the average TB Advantage for all actively marketed bulls is +1.

“All of this means that UK farmers will have plenty of choice when selecting bulls to breed their dairy replacements, and suggests that the bulls with the poorest indexes for TB Advantage, as with other key traits, will never reach the market,” he says.

However, he is keen to remind breeders to keep any single trait index in context, and to use it only as part of a broader breeding strategy which takes on board all of the considerations which are important to a business.

Furthermore, he remarks:
“Farmers should be aware that the reliability of the TB Advantage – or its likelihood of not changing over time as more data is added – is not as high as for most other indexes.

“This reflects the fact that bovine TB is not a problem for many of the countries with which we traditionally share genetic information so we are using a smaller dataset than would be the case when assessing many other traits.

“Of course, this doesn’t mean the index won’t be valuable in predicting future performance and if all other traits are equal, it would definitely be preferable to use a bull with a positive TB Advantage,” he says.

The new index has been widely endorsed across the farming industry who see it as an effective long-term strategy which will have cumulative benefits over the generations.

However, all are equally keen to point out that current disease control measures must continue to be adhered to as part of the UK’s bTB eradication strategy.

Department for Environment, Food and Rural Affairs (Defra) Minister of State, George Eustice, said:
“England has the highest incidence of bovine TB in Europe which is why we are taking strong action to deliver our 25-year strategy to eradicate the disease through tighter cattle measures, improved biosecurity and badger control in areas where the disease is rife.

“Reducing the risk of disease entering a farm is crucial to end the devastation bovine TB causes for farmers and rural communities.

“We welcome the new AHDB TB Advantage index which can help dairy farmers select bulls for their herd.”


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