BVD in the dairy herd: now and next

Farm vet Vikki Wyse discusses BVD in the dairy herd, including the best ways to protect your herd and how the disease may be eradicated.

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The UK BVD eradication programmes are making good progress, but BVD still remains an issue of concern until eradication is complete. The persistently infected (PI) animal is central to the control of BVD on-farm, and so eradication centres around:
1. Identifying and removing PIs
2. Biosecurity to prevent introduction of BVD
3. Effective vaccination to protect the fetus

Protecting the herd

Biosecurity is hugely important, and the fourth National BVD Survey revealed an on-going theme, particularly that not all closed herds are actually closed. BVD breakdowns continue to be reported across the country, often due to an oversight when purchasing new stock, such as in-calf animals where the unborn calf had been exposed to the virus. Another common way the virus gets into a herd is when stock is moved to a field without double fencing and encounters BVD positive neighbouring stock. Of the “closed” herds in the survey 2% rear calves away, 19% bring bulls in, 2% buy in heifers or cows and 1% purchase fattening stock. Hence the need for ongoing surveillance, good biosecurity and vaccination to maintain herd protection.

Choosing the best testing options

A BVD Control Strategy is now part of the Red Tractor standards, so we advise all farms to have a plan in place for routine testing, plus control and eradication if required. The simplest and most cost-effective means of routine monitoring is to use the Tag&Test tags at around  5/animal. This is also the most used method in the UK at 33% of farms, up from 27% in 2018.

However, only 42% of producers are tagging all calves born, dead or alive, which is concerning. Failing to tag all calves means that a PI can stay on farm without detection, causing health and productivity problems, with disastrous effects on a farm’s eradication policy. Other methods include regular bulk milk screening for the presence of virus, and youngstock screening. We can help you find the best monitoring methods for your herd. If you’re not using tags, we recommend twice yearly routine youngstock screen (homebred unvaccinated 9-18 months old) and any bought-in animals, plus quarterly bulk milk virus (PCR) testing.

Should I cull the PIs? Can’t I just fatten them?

PIs should be removed when identified, and yet the survey revealed that nearly half of farmers retain them. The reasons producers held onto PIs were because the animals looked healthy, they doubted the result, they had successfully reared PIs to slaughter or another farmer advised them to.

Among farmers that had identified a PI animal 44% decided not to cull them immediately.
77% of those animals then either died before reaching a productive size, or had to be treated for other conditions.
When asked whether they would knowingly retain a PI animal again, 93% said they wouldn’t.

My bulk milk is positive, but I don’t think I can see any impact of BVD on my herd…

Unvaccinated cows in positive herds, without overt signs of disease:
• Lost up to 10% of their yield per day
• Had significantly lower 305-day milk production, fat and proteins
• Were twice as likely to be culled because of decreased milk production

Is Vaccination Worth the Cost?

Biosecurity can be problematic in the best of herds and vaccination is an effective way to protect the unborn fetus and help break the cycle of infection. In England most herds vaccinate, with key selection criteria being ease of use and the ‘best vaccine for the job’. Most farmers who vaccinate do so on vet recommendation and as an insurance policy i.e. to prevent infection rather than waiting until exposure or signs of infection occurring. Most producers estimate the impact of BVD to cost £44-100/cow/year. The economic benefit of vaccinating a dairy herd with Bovela , on milk production alone, is up to £56 per cow per lactation. Most producers also noticed a decrease in calf diseases, followed by improved fertility and decreased antibiotic usage, which is certainly a hot topic at the moment.

Increasingly farmers are opting to use Bovela  BVD vaccine, due its proven 12 months’ duration of protection and easy one dose starter and annual vaccination schedule, and is now the UK’s market leading BVD vaccine.

Eradication of BVD can be achieved, and this latest survey shows how seriously the industry is taking this important disease. For more information see https://bvdfree.org.uk/ If you would like to discuss any aspects further, then get in touch with the practice or directly with your routine vet.

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