TB Herd History Risk Statements: What do they entail?

The Department of Agriculture, Food and the Marine has issued Bovine TB Herd History Risk Statement and Report letters to thousands of livestock farmers around the country.

But what do these letters contain – and how is one’s herd history risk calculated?

The statements break down Irish herds into 12 status risk categories.

The first code is INF, which means that a herd is currently restricted; the latter 11 categories include codes listing from C0 to C10, with C0 herds explained as herds clear of TB for less than one year (i.e. zero years), and C10 defined as herds clear of TB for 10 years or more.

The remaining nine codes (C1-C9) are defined as the number of years a herd has been clear of TB. In addition, a figure in brackets is given which indicates the number of TB breakdowns had by recipients’ herds in the last 10 years.

The letters state: “All herds do not have the same risk of a future TB breakdown.”

Much of this risk, the department says, is based on the following:
  • How long it is since your herd last had a breakdown;
  • How severe that breakdown was;
  • At-risk animals in your herd;
  • Your purchasing history.

The statement and report letters say: “This report provides information about your purchasing pattern from herds within different risk categories. It also details the animals within your herd which are at a greater risk of testing positive for TB in the future.

“To minimise the chances of your herd developing TB you should consider very carefully the TB risk of herds you purchase animals from – particularly breeding stock, including stock bulls.

“The longer a herd you buy from has been clear of TB, the less likely it is that your herd will go down with TB from this source,” the letters add.

A purchasing history by risk is produced for individual herds, which details the percentage summary of movements to your herd over the last three years by the current risk category of source herds.

In a breakdown of the national purchasing history by risk in 2019, it was noted that, last year, 63.5% of purchased cattle came from lower risk category (C7-C10) herds, 11.8% originated from medium risk  (C4-C6) herds and 24.7% were from higher risk (INF-C3) herds.

Finally, a summary of outward movements from the individual recipients’ herds in the last 12 months is given with the figure showing the number of animals which were classified as: mart movements; farm-to-farm movements; factory; abattoir; export; and knackery destinations.