The Bovine Viral Diarrhoea (BVD) positive retention rate has fallen “considerably”, according to the latest figures from Animal Health and Welfare Northern Ireland (AHWNI).
The figures highlight the impact that BVD herd restrictions are having on infected farms across Northern Ireland so far this year.
Since the beginning of March, four herds had retained five BVD positives for 28 days or longer. The cut-off point after which herd restrictions are now applied is 28 days from disclosure of the positive result.
This compares to 11 retained BVD positives in eight herds at the start of February and 17 retained positives in 11 herds in early January.
The aim of reducing movements is to reduce the risk of virus transmission, and to drive down the length of time for which BVD positive animals are kept on farm.
From May 1, herd restrictions will be applied seven days after a positive or inconclusive animal is disclosed, unless the animal is disposed of or in the event of a negative retest before the seven day period elapses.
From June 1, 2025, herd restrictions will be applied to those herds that have more than 20 cattle greater than 30 days of age of BVD unknown (BVDU) status.
AHWNI has encouraged all farmers to get BVDU cattle tested as soon as possible, by using supplementary tags or by getting blood samples taken by a private vet.
The reason for these herd restrictions is to prevent the BVD virus moving out of herds that have a potential reservoir of infection in untested cattle, according to AHWNI.
All cattle born before the start of the compulsory scheme have now been assigned a BVDU status and require testing before being moved off the farm.
As infection levels decrease, a decrease occurs in the levels of natural immunity to BVD in herds, according to AHWNI.
This means that the likelihood of pregnant cattle being exposed to the virus is decreasing but susceptibility to infection may increase because there is less natural exposure to the virus.
Vaccination induces a protective immunity in breeding animals to help avoid a range of negative outcomes of infection including failure to conceive, abortion, birth defects and most importantly the creation of calves that are persistently infected with BVD virus.
The decision whether to vaccinate or not depends on the risk profile of the herd and should be discussed with the farm’s veterinary surgeon.
