More than 2,000 cattle on farms in west Wales were slaughtered in the first six months of this year because they tested positive for bovine TB.

According to figures released by DEFRA, there were 237 new herd incidents in Pembrokeshire, Ceredigion and Carmarthenshire between January and August.

During this period, 318,261 cattle were tested and a total of 2,110 reactors were culled. The National Animal Disease Information Service (NADIS) suggested improving herd bio-security would reduce the risk of disease entering a herd.

Most cattle infected with TB showed no signs of the disease and examination alone would not detect infected animals, said NADIS vet Mike Howe, who is based in Pembrokeshire.

"Before cattle are brought onto a farm, farmers with their vets should do a risk assessment to estimate the risk that these cattle will also bring in TB," he said.

If there is a significant risk then strategic testing should be undertaken, advised Mr Howe.

"While no testing regime can provide 100% certainty, planned TB testing is a great improvement on the current situation where most cows are bought with little thought as to their TB status.''

A report written by Richard Laven, manager of the Scottish Agricultural College's surveillance centre, said cattle should only be purchased from a known background and TB results requested from the selling farm.

"Isolation and testing significantly reduces the risk of TB entering farms that are not closed and provide a practical way of improving bio-security for the prevention of the spread of bovine tuberculosis,'' he said.

Research by the National Animal Disease Information Service, a network of veterinary practices and colleges monitoring diseases in the UK livestock industry, is sponsored by the Milk Development Council, the Meat and Livestock Commission, Elanco Animal Health and Intervet.