Bovine Viral Diarrhoea (BVD) continues to negatively impact herd performance and productivity across many Welsh farms and is estimated to cost beef farmers £45 per cow per year. Support is now available by the Welsh Government to reduce the financial burden of BVD as they launched a new scheme on the 1st of September 2017 that will run for three years. Free blood sampling will now be available for youngstock during routine TB tests in order to identify infected herds with additional financial support of up to £500 available for herds found to be infected.
What is BVD and its symptoms?
BVD is a highly contagious pestivirus that can impose a wide range of symptoms whilst varying in severity. Poor fertility amongst both male and female cattle is one of the main symptoms of BVD as it contributes to reduced conception rates and early embryonic death, abortion, stillbirths as well as weak premature calves. In non-pregnant cattle and young stock, it increases the severity and prevalence of other disease such as pneumonia and scours through immunosuppression whilst also reducing feed intake.
How does BVD spread?
BVD can spread through urine, faeces, direct nose to nose contact with carriers, through the semen of infected bulls and from infected damns to their unborn calves. When an individual animal becomes infected with the virus, it will usually remain present in the animal for about two weeks making them infectious to others during this time. After two weeks, the animal will build an immunity to the virus for a period of time by producing BVD antibodies.
BVD can also be spread through persistently infected animals (PIs). A PI calf is produced when a pregnant damn becomes exposed to the BVD virus within the first 30-120 days of pregnancy, and pass the virus through the placenta to the unborn calf. The unborn calf has no immunity to the virus and will remain infected throughout its life and shed a large amount of virus. PI animals will fail to thrive showing poor growth, rough coats and may die, but a significant proportion will survive and appear normal whilst continuing to infect other animals. It is important to remember that a PI animal that will survive until breeding will always give birth to a PI calf. If a cow becomes infected during late pregnancy, she will not produce a PI calf but will occur other fertility problems such as abortion and calf deformities.
Testing for BVD
If a herd’s BVD status is unknown, testing can be carried out through blood sampling, tag and test or through bulk milk samples.
For youngstock, tag and test all calves at birth with Tissue Sampling Tags that collect ear samples whilst the animal is being tagged. Send the collected tissue samples in a labelled, air tight container to a laboratory where it will be tested to identify whether the animal is a PI. In older calves, blood sample 5-10 calves (minimum of 5 per separately managed group) aged 9-18 months for the presence of BVC antibody. If they test positive, this indicates that they have been recently infected and that BVD is a concern and that more tests need to be done to understand fully where the problem lies. Within dairy herds bulk milk can also be tested for the presence of BVD antibodies.
Once it has been indicated that there are BVD or any PI animals on the farm, steps can be taken to eradicate the virus by removing any PIs and working with the vet to set up a vaccination programme and ensure that there are adequate biosecurity measures in place.
To find out more, click here to contact a Wynnstay Beef Specialist.