Agriculture Minister Andrew Muir has set out the criteria against which farmers will be required to use the interferon-gamma blood test for TB.

Initially, herds with 10 or more skin reactors at a test, or herds with more than 40 reactors within a rolling 12-month period, will be required to undertake mandatory blood testing, although this will not apply to beef fattening herds.

Animals that have given an inconclusive reaction to a skin test in non-breakdown or single reactor herds where TB has not been confirmed, will also have to be blood tested.

The blood test has a higher sensitivity than the skin test, so it will miss fewer TB infected animals. However, it has a lower specificity and therefore will lead to more “false positives” than the skin test, which is why it is not used more widely across herds.

The changes will come into effect from 29 June 2026.