AgriSearch co-funded studies have played important roles in both the decision by Animal Health and Welfare Northern Ireland (AHWNI) to implement a BVD eradication programme for Northern Ireland and in the structure of the programme.
In the first study 181 dairy herds were selected providing a geographical spread around NI. Bulk tank milk samples were collected over 3 years to monitor antibody levels to BVD and IBR. In addition, the first sample from each herd was tested for the presence of BVDV virus.The second study included 589 dairy and suckler herds from across NI that were undergoing a brucellosis herd test. Blood samples from 5-10 young stock (12-24 months old) from each farm were tested for antibodies to BVD.Both studies included questionnaires on herd management. The data has given a picture of current management practices within NI herds. The results obtained generated the following key messages:
The first study showed that a high proportion of NI dairy herds were seropositive to BVDV: over 85% had high levels of antibodies to BVD in their bulk milk and in nearly 10% of the herds BVD virus was detected in the bulk milk.
Identification and removal of persistently infected (PI) animals is essential for BVD control. Most of the dairy herds with active BVD infection (positive for BVD virus in the bulk tank milk) were already vaccinating for BVD.
A high proportion of NI dairy herds were seropositive to IBR. The use of conventional IBR vaccine makes the results difficult to interpret. It is recommended that only marker vaccines that allow differentiation between infected and vaccinated animals should be used.
The second study showed that exposure to BVDV is very widespread in NI dairy and suckler herds, 66% of all herds tested had at least one seropositive animal within those tested. In the context of control and eradication, these herds would require further individual animal sampling.This high prevalence of seropositive animals supports a NI programme that directly identifies PI animals (similar to programmes in Switzerland, Germany and Republic of Ireland (ROI)) over those which use initial serological screening to categorise herds (Scandinavian approach). Another advantage is the ‘two for one’ result. All PI dams will have PI calves so a calf that is not PI will have a dam that is not PI.
A copy of the full report can be found by clicking here