Genetic index to breed out bovine TB

The TB Advantage, a genetic index that could help UK farmers breed dairy cows with better resistance to bovine TB (bTB), is to be published from mid-January.  

The index is claimed to be the first in the world to help farmers combat bTB through breeding stock that has a genetic resistance to the disease. It will indicate an animal’s genetic susceptibility to bTB, highlighting those with a higher degree of resistance, as well as those that may be more prone to the disease. BTB susceptibility will be indicated in the scale by a score ranging from -3 to +3, which is similar to the scales used in many other genetic indexes. The average TB Advantage score for bulls with an index is zero.      

The initiative was developed through extensive research at the University of Edinburgh, the Roslin Institute and Scotland’s Rural College (SRUC), with support from Defra, the Welsh Government and the Agriculture and Horticulture Development Board (AHDB). The AHDB will publish the TB Advantage index three times a year as part of routine genetic evaluations. Almost all Holstein bulls, daughter-proven and young genomic sires, will have an index, and female Holsteins that have had their genotype measured will also be scored for the TB Advantage list. 

The AHDB says that together with the current bTB control measures, the index could play a part in eradicating bTB from UK farming.   

“Tackling any problem through breeding is a long-term, sustainable approach and can yield worthwhile rewards,” says Marco Winters, head of genetics at AHDB. “However, breeders of dairy cattle have to consider a number of traits that are important to their business and their cattle, and breeding for TB resistance should be only a small part of their broader breeding strategy. 

“This index is another tool in the breeding armoury. Once a farmer has shortlisted the bulls which meet his other chosen breeding criteria, it will always be best to avoid those which have a poor index for TB Advantage. We know that improvement through breeding is a long-term approach to any problem but this will stack the odds of fighting bTB in the farmer’s favour and play a part in the plan to eradicate bTB from the UK,” he concludes.