With all of the hype recently regarding M.bovis there is even greater appeal for keeping a closed herd where possible. With this in mind, it is just as important to ensure the animals you are keeping for replacements are healthy and disease free. At this time of year it is as relevant as ever to address the ever present issue of BVD infection on farm, and it’s impacts on breeding and rearing replacements.

BVD is one of the major diseases affecting dairy cattle across the country and is responsible for a staggering loss in production. It is estimated around 80% of dairy herds in New Zealand have been exposed to BVD virus and the disease alone is estimated to be responsible for a loss of $70,000 annual for an average sized dairy farm.

BVD is a viral infection which causes many non-specific clinical symptoms ranging from diarrhoea, ill thrift, abortion or weak calves to the suppression of the animals immune system. It spreads very easily between animals from nasal discharges, milk, faeces or mating. If a pregnant animal becomes exposed to BVD in the first four months of pregnancy she will produce a calf that is persistently infected (PI). This animal will shed the virus throughout its life and will be the main source of infection on the farm.

So why think about BVD now?

PI calves are the main source of spreading infection on farm and are also responsible for the production of more PI calves, perpetuating the exisiting disease. If you are breeding replacement heifers or are planning to, its is important to ensure you are not producing PI calves. BVD eradication can be a lengthy process but we are here to talk you through every step of it.

Step 1: IDENTIFY the risk by confirming exposure to BVD on your farm, through a bulk milk test. This test can also identify the presence of a PI animal. Remember that bulk milk tests only cover the animals contributing to the bulk tank, therefore it will not include any dry, colostrum or penicillin mob cattle, or any young stock on farm. Peak lactation can be a good time for testing as you will have the maximum number of animals in the milking herd. Make sure your signed up for BTM testing.

Step 2: assess BIOSECURITY using the In, Out, Over
method:
In: test any cattle brought into the herd - including
bulls!
Out: Remove any identified PIs
Over: reducing contact with neighbouring cattle
through boundary fences

Step 3: TAKE ACTION! This is the time of year to start and each action plan should be tailored to your farm and your
level of infection / risk. Herd vaccinations - especially in your heifers. Primary courses of vaccinations require two vaccinations 4 weeks apart and must be completed at least 2-4 weeks before planned start of mating date (PSM). Vaccinating breeding animals protects against producing PI animals in future seasons. If BVD is an issue - ear notch testing every calf is an important way to identify a PI animal. If you would like to find out about BVD on your farm, or need some tailored advice to getting rid of the disease, please contact your VetEnt Clinic and we will be happy to help.

17 October 2018, 03:58
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