BVD

Our autumn bulk milk BVD tests are in, and we have noticed that many farms in the district have seen a major jump in the level of antibody circulating. So… is there more BVD in the area? Are our herds protected?

You have probably noticed that we biannually test your herd’s milk for evidence of BVD. It’s not just looking to see if your cows are infected with a virus; it is to protect you from reproductive losses. BVD has the potential to significantly decrease your pregnancy rates, which is why we are so concerned with keeping an eye out for it in your herd.

This year, a lot of farms have seen a large spike in their levels of antibody. It is common to see an increase in autumn due to lower milk volumes, but these increases are much greater than normal.

What is BVD?

Basically, BVD represents a huge risk for reproductive losses on farm. It is a virus that may affect your herd in a variety of ways, the most significant of which being through losses around mating and pregnancy.

·         If cows are pregnant when infected, they may abort or produce an offspring that is persistently infected (PI).

·         PI animals pose the biggest risk to your herd as they are persistently shedding huge volumes of the virus, meaning that pregnant animals are at a greater risk of becoming infected and aborting their calves in the season following the birth of a PI.

· Infected bulls will have decreased fertility and will also reduce the reproductive performance of your herd.

Are you at risk of being affected by BVD?

The greatest risk factors for being affected by BVD include:

·  animals of unknown disease status being introduced to the farm.

· grazing animals on blocks where they are likely to be exposed to BVD though

interaction with infected animals from other farms.

· over boundary fences (i.e. from infected animals on neighbouring properties)

·       leasing infected bulls.

How should you monitor for BVD?

Given the huge potential risk that BVD poses, we biannually screen for evidence of exposure using a bulk milk samples, typically in early lactation so that as much of the herd as possible is screened.

· It is important that any animals that are not being milked into the vat are recorded at this time.

·      If this test indicates that there has been a change in the infection status of your herd, we initiate an investigation into finding the animal(s) responsible.

·    It also allows us to evaluate the level of protection against BVD is in your herd- ie whether or not you are vulnerable to the disease and should consider vaccination.

·      These animals are identified and culled, ideally prior to the start of the mating period, so that abortion risk and foetal losses are minimised. 

You can also test your replacements to see if a PI has been created and potentially about to be introduced to the herd. 

Can you prevent BVD?

·     BVD can be prevented by managing biosecurity risks, such as through minimising contact with animals from outside of your farm.

·    PI creation can be prevented through vaccination of susceptible dams to prevent pregnancy losses. 

·     When bringing new animals onto your property, it is important that they are not infected with the virus.

o   Ensure that bulls originate from BVD free farms and have been tested to confirm that they are not PI, and that they have been vaccinated.

o   Also confirm that they are not transiently infected, as this will affect their reproductive performance, again resulting in decreased pregnancy rates.