ICBF TB scoring – What farmers need to know
The TB score has an influence of 2-3% on a total EBI animal profile. Picture: Andy Gibson
Selectively breeding for TB resistance should be seen as valuably as vaccination, according to one of the ICBF’s senior geneticists.
Siobhan Ring spoke with the about the ICBF tuberculosis (TB) scoring on animal profiles and what this could mean for your upcoming breeding season.
“Breeding for TB resistance is a bit like vaccination. You’re protecting yourself for the future, it’s not something you do as a reactive thing. Any farmer that tells you it doesn’t interest them, should think again because TB impacts everybody, whether you’ve been locked up or not,” said Ms Ring.
The TB scores for animals were first introduced in 2019 on a trial basis via the active AI bull list on ICBF. By the end of 2023 TB scoring was added to the EBI and can now be found on all indexes and individual animal profiles.
“We [ICBF] categorise animals when they are calves and then we follow them through throughout their lifetime. What we see is that animals that were genetically ‘high risk’ for becoming reactors, they would have 26% more TB reactors than calves that ICBF have labelled for ‘low risk’ for becoming TB reactors,” explained Ms Ring.
The data used for the TB score is a combination of genomic and phenotypic data. When a calf is born and a sire and dam are listed or when that calf is tagged and genomically tested, progeny data from the sire and dam is used and applied to the calf. This data is accumulated from daughters of the calf’s sire and dam as well as sibling data.
With the TB score farmers will also see a ‘reliability’ figure on their animal profiles. This is not a new concept for regular users of the ICBF’s services and profiles across beef and dairy. For TB scoring, an animal with high reliability means the animal is well-proven with genomics, progeny, and sibling data.
Farmers might notice older animals within their herds might display lower reliability scores compared to their younger herd mates. This is because older animals are more genetically removed from the majority of animals being tested and logged today.
The phenotypic data is provided to ICBF by the Department of Agriculture (DAFM) every two months to ensure all figures are current and up-to-date for animal profiles. DAFM provides information and results of TB skin tests conducted on farms and TB-confirmed lesion cases found at factories.
All data is given equal weight when creating the score for each animal. However, it is important to note that ICBF uses data from herds that have had confirmed cases of TB. No data is reviewed from herds which have never had confirmed TB outbreaks.
Overall, a TB score only influences an animal's EBI by 2-3%. The TB scores are calculated using mixed model equations – an equation that takes into account fixed and random effects. Since the scores’ inclusion into the indexes in 2023 it makes up two thirds of the health sub-index within the EBI.
“Breeding for TB resistance is not just for the herds locked up today… You want to future-proof the next generation so how you can do that is through the bulls you are selecting this spring,” Ms Ring explains.
Farmers who are selecting bulls with high health scores are subsequently improving TB scores without having to change any of their current practices. The average bull TB score is 8.5. This means “if a herd gets locked up we expect that 8.5% of a bull's progeny will be infected with TB.”
When discussing what farmers should do when selecting their bulls Ms Ring said: “The lower you can get that TB score the better, but don’t forget to maximise the EBI.”
Based on demand ICBF has now made the TB score on herd profiles more accessible for farmers ensuring it appears on the first page on herd and animal profiles.
“This year there have been improvements on the website to ensure the TB score is front and visible on every herd’s animal search. There are 30 traits on the EBI, four to five years ago there is no way that TB scores would have come to the front screen… Just goes to show how quickly things change as we adapt to the demand,” explained Ms Ring.
If you have been affected by the recent increase in bovine TB rates in Ireland and would like to speak with a journalist, please contact our Farming reporter Zoe Geary at zoe.geary@examiner.ie.
