< World’s First bTB-Resistant Bull Proofs Announced at British Cattle Conference
Macro Winters

British Cattle Conference delegates were among the first to hear about the new genetic index for Holstein bulls, designed to allow producers to select bulls whose daughters have high levels of resistance to bTB.

AHDB Dairy’s genetics expert, Marco Winters said the index was a world-first and the result of months of research, which had examined hundreds of thousands of cow records. The ‘TB Advantage’ index is expressed using a scale of -3 to +3, with many of the highest Profitable Lifetime Index bulls showing a positive score.

Mr Winters said:

“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.

“This is reassuring, as it indicates that cattle breeding is already heading in the right direction. It is also unsurprising, since health and fitness traits represent an important component of PLI.”

Health and fitness represent around 68 per cent of PLI, with analysis revealing a favourable correlation between the TB Advantage and general health and fitness, he told the audience. 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 breeding progress is being made,” he said. “Taken from a complete dataset of bulls whose average TB Advantage is zero, only the best bulls are marketed to UK farmers. This explains why the average TB Advantage for all actively marketed bulls is +1.

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

However, Mr Winters reminded breeders to consider any single trait index in context and to use it only as part of a broader breeding strategy, which takes into account all of the other factors important to a business.

“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 does not mean the index will not be valuable in predicting future performance. If all other traits are equal, it would preferable to use a bull with a positive TB Advantage.”

The new index has been widely endorsed across the farming industry, where it is seen as an effective, long-term strategy which will have cumulative benefits over the generations. However it must be remembered that current disease control measures should be followed, as part of the UK’s bTB eradication strategy.