Keepers of breeding herds of cattle in Scotland must have their herds screened every year for BVD. There are two options available for 'not negative' herds and three for 'negative' herds.
You do not have to individually test every animal in your herd to find out if you have BVD. Instead, you can do a screening test which will indicate if BVD may be present in your herd. Once you have done your screening test the result will tell you and your vet whether you are free of BVD or whether you need to do follow-up testing to find out if there is an active BVD infection in your herd.
Your vet will be able to provide further advice about which method should be used and whether it is appropriate to test for antibodies to BVD or BVD antigen/virus in your case. You must use one of the following methods:
Mandatory annual screening methods for breeding herds with a 'negative' status
0. NEW - The dairy check-test - for year-round calving 'negative' herds
The standard check test is appropriate for herds that have distinct block calving periods. In dairy herds that calve all year round it can be difficult to ensure that the heifer groups are surveyed properly. To ensure that exposure is detected in these herds more animals must be sampled more frequently.
If you have a dairy herd that calves all year round, your vet should blood sample no less than 10 calves between the ages of 9-18 months, the youngest and five oldest unvaccinated cattle within each group. This test must be carried out twice per year at roughly six months apart, more than seven months apart will indicate an expired test result. If you have a dairy herd that calves in distinct seasons you can use the normal check test providing all separate groups are tested.
The number 0 has been allocated for the dairy test in order that the database can recognise that the dairy check-test has been used.
1. Sampling calves - the check-test
Whenever possible for a check test, use Option (a) below. Where this is not possible options (b) and (c) should be followed in order. All of these three tests are for antibody.
Before deciding to do a check test, speak to your vet to identify how many separately managed groups you have in your herd. Your vet will decide how many animals need to be tested.
(a) Five calves aged 9 to 18 months
Take samples of blood from not less than five calves in the age range 9 to 18 months in each separately managed group. If there are fewer than five calves in a group, then test all the calves in the group.
(b) Ten calves aged 6 - 18 months
If any of your sample of calves are aged 6-9 months, then take a sample of blood from not less than ten calves in the age range 6 to 18 months in each separately managed group. If there are fewer than ten calves in a group, then test all the calves in the group.
Shetland only: in recognition of the successful eradication of BVD from Shetland, you may take blood from not less than five animals in the age range 6-18 months. If there are fewer than five calves in a group, then test all the calves in the group.
(c) Five over 18 months and on the holding since birth
If you have no calves in either of the above age categories, but only then, can you choose to use the following method:
Take a sample of blood from not less than five animals that have been on the holding since birth in each separately managed group.
Mandatory testing methods for breeding herds with a 'not negative' status
2. Calf screen - test all calves
Individually test all calves born in the herd in the past year for virus by blood or tissue sample. You can test the calves as they are born or all at once. Ear tissue tag testing (explained below) can be a particularly useful way to do this and is the only method, apart from 'method 3: Test all animals' (detailed below) which you may do without the assistance of a vet.
Ear Tissue Tags
Ear tissue tags are designed to take a tissue sample from the ear whilst tagging the animal. The tissue goes into the labelled capsule when the animal is tagged, which is then snapped off and sent to the laboratory.
If you want to purchase ear tissue tags then contact your usual ear tag supplier. If they do not stock them they should be able to direct you to somewhere that does.
3. Whole herd screen - test all animals in the herd
Individually blood or tissue sample all the animals in the herd within that year. This is a test for virus and has the advantage that all the persistently infected (PI) animals in the herd can be identified and removed. The farmer may choose to tissue tag everything, in which case a vet does not need to be consulted, however, if they choose to take blood samples a vet will need to be involved. If all the animals are negative for BVD virus this will constitute a negative result for that year.
This testing method is the most expensive option, but it may suit herds where BVD infection is suspected or herds where no other method is entirely suitable.
Important welfare note on ear tagging
If you wish to use ear tissue tags you should, if possible, use those that are also the official ID tags, either primary or secondary. Applying additional ear tags can cause welfare problems for cattle.
If you decide to use ear tissue tags, make sure you use the correct applicator – some may appear to work with other tags but can apply them too tightly, causing pain and leading to infection.
Testing options summary table:
|No ||TESTING OPTION ||DAIRY/BEEF ||TEST FOR ANTIBODY/ANTIGEN |
|0 ||Dairy with year-round calving |
10 animals 9-18 months twice a year
|Dairy ||Antibody |
|1a ||5 animals between 9-18 months per separately managed group ||Either ||Antibody |
|1b ||10 animals between 6-18 months per separately managed group |
Shetland only: test five animals from this age range
|Either ||Antibody |
|1c ||If neither above are possible - 5 animals 18 months+ on holding since birth per separately managed group ||Either ||Antibody |
|2 ||Calf screen ||Either ||Antigen/Virus |
|3 ||Whole herd screen ||Either ||Antigen/Virus |
Antibody: Tests for exposure to the virus
Antigen/Virus: Tests for the presence of virus
Persistently Infected cattle (PIs)
Cows that get infected with BVD in their first four months of pregnancy can give birth to a persistently infected (PI) calf. These PI animals are the major source of BVD infection, as they will have the virus all of their lives and spread it in huge quantities. Many will die within the first year of life, but some can live much longer and may appear normal. Cattle infected with BVD after birth are transiently infected and will normally recover in around four weeks, but do suffer from a reduced ability to fight other infectious disease and are likely to have impaired fertility until they recover.
Health Scheme Members
Most herds fully participating in the CHeCS BVD programmes meet the testing requirements. If you are testing BVD as part of your health scheme membership you need not do anything extra, but check with your vet.
Separately Managed Groups
The correct identification of each separately managed group is critical to the effectiveness of check-testing. A management group consists of those animals that can be freely achieve nose to nose contact with all others within the group.
The virus relies on PI animals as they spread the virus efficiently when in nose to nose contact with other cattle. Housing with trough feeding will ensure repid spread whereas spread will be slower among cattle at grass.
Because BVD spreads so easily it is not necessary to test every animal in every group. Five animals are sufficient providing the following conditions are met:-
- All the animals in the group have been together with close contact for at least two months
- They will have had nose to nose contact during that period
- You must consult a vet when identifying the separately managed groups in your herd before choosing animals to be tested.
The second point about nose to nose contact is important when deciding about housed animals. Animals either side of a central passageway for example are separately managed groups.