New breeding figures will help in battle against TB

Published 18 February 16

The new TB Advantage index, launched by AHDB Dairy on 19 January, is set to improve resistance to bovine tuberculosis (bTB) in herds – without compromising on other important fitness and production traits. 

Marco 4.155220

Expressed on a scale which, typically, runs from -4 to +4, Marco Winters, head of genetics for AHDB Dairy, says many of the highest Profitable Lifetime Index (£PLI) bulls also have a good positive score for TB Advantage. 

“£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. The youngest sires with the most modern genetics have, on average, the highest TB Advantage, with scores ranging from -2.2 to +3.3 for the actively marketed group.” 

Top 5 daughter-proven bulls ranked on Profitable Lifetime Index (£PLI) showing new TB Advantage (January 2016)

Rank £PLI £PLI Rel % Bull Name TB Adv TB Rel %

Company

GB

Company

NI

1

603 83 KINGS-RANSOM ERDMAN CRI 0.3 49 BUL AIS
2 599 91 GEN-I-BEQ LAVAMAN 1.6 48 SMX SMX
3 591 75 DE-SU RANSOM 1.1 43 TAG  
4 573 73 CO-OP ROBUST CABRIOLET 0.7 43 BUL AIS
5 570 77 NO-FLA ALTAEVERGLADE 0.2 44 ALT GG

Top 5 young genomic bulls ranked on Profitable Lifetime Index (£PLI) showing new TB Advantage (January 2016) 

Rank £PLI £PLI Rel % Bull Name TB Adv TB Rel %

Company

GB

Company

NI

1 724 64 SANDY-VALLEY-I PENMANSHIP 1.3 41 SMX SMX
2 683 63 STANTONS CHECKERS 0.4 43 SMX SMX
3 682 63 APINA NADAL 1.5 43 GEN GEN
4 676 63 SEAGULL-BAY-MJ SOLARIS-ET 0.9 40 GEN GEN
5 665 63 TOPCROFT PESKY TRIX 1.5 42 GEN GEN

Key: ALT = Alta; BUL = bullsemen.com; GEN = Genus ABS; SMX = Semex; TAG = Trans-America Genetics; PLI = Profitable Lifetime Index; Rel % = reliability.

Marco explains that the TB Advantage is calculated using data from about 650,000 animals in herds which have reactors to the official bTB skin test. “Those that react to skin tests, or who show no outward signs but have lesions when slaughtered, are the ones with a susceptibility. By comparison, their herdmates who are also likely to have been exposed to the disease yet simply do not contract it or react in any way to it are the ones we want to identify, as they are the ones with better inherent resistance.” 

“In real terms, the index indicates the degree of resistance to bTB a bull is predicted to pass on to his offspring and is expressed on a scale which, typically, runs from -4 to +4. 

“For every point of a bull’s TB Advantage, one per cent fewer daughters are predicted to become infected during a TB breakdown. The difference between daughters of the best (approx +4) and the worst (approx -4) bulls is, therefore, around six per cent. This means that six fewer cases of bTB could be expected per 100 cows in one generation if the best bulls are chosen over the worst. As with all genetic improvement, the benefits are cumulative, building up over the generations.” 

Tim GueTim Gue, who milks 400 cows at Huddlestone Farm near Steyning in West Sussex, says the release of TB Advantage has at last given farmers a tool that should, over time, increase resistance to bTB in both their own cows, and in any animals they may be marketing to higher risk areas.   

“This new information is used in the same way farmers have used other health trait indexes in the past: don’t use those bulls that are poor for bTB resistance and, if choosing between two bulls that are otherwise similar, pick the one with the better TB Advantage.” 

“The positive relationship between £PLI and TB Advantage means farmers don't have to compromise other breeding goals. Therfore, bulls with high health traits will usually have good TB Advantage scores, although as ever with genetics there are outliers, so it’s important to check.” 

Tim adds that despite West Sussex being a low risk area, he’ll be keep a close eye on the TB Advantage scores of bulls he uses at Huddlestone. “We may wish to sell stock into higher risk areas in the future and, sadly, the incidence of the disease shows no sign of reducing anytime soon.” 

TB Advantage sits alongside other current disease control measures and must continue to be adhered to as part of the UK’s bTB eradication strategy. Further information on all bTB control measures, the TB Advantage and other aspects of bTB can be found at the recently launched TB Hub