Friday, March 29, 2024

Keeping BVD out the best option

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A Hamilton pathology company hopes a shift in focus around bovine viral diarrhoea (BVD) detection will significantly reduce its occurrence in cattle herds.
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The insidious and complex disease has been under increased scrutiny by the pastoral sector over the past decade, with its main symptoms of ill-thrift, empty cows, deformed calves and poor production often confused with seasonal conditions or other diseases.

Hamilton-based SVS Laboratories chief executive Richard Campbell said the focus on bulk testing milk samples in recent years has proved effective in identifying if herds had the disease.

“However, if we are serious about actually reducing the number of infections in herds after almost a decade of monitoring it, we need to start identifying new replacement animals coming into herds that are carrying the infection in the first place.”

His company decided to embark on a campaign to push farmer awareness of the disease beyond a straight “monitor and cull” approach, to a more preventive phase that tested replacement animals before they entered the main herd.

The nature of the complex disease meant it could be passed on in-utero from mother to calf, should the cow become infected before or during pregnancy.

Work done late last decade by a BVD steering group found 60% of herds had been exposed to BVD and 15% were infected at any one time.

The group estimated the average cost of the disease was $20,000 a year per infected herd, with a national cost to the dairy sector of $30 million a year.

Campbell said NZ risked being left behind by countries including Ireland that were embarking on campaigns to eliminate the disease. Switzerland already claimed it was eliminated.

“But, given NZ’s free market, subsidy-free environment and the fact BVD does not have a human health risk, unlike, say, leptospirosis, we are unlikely to see such a campaign here.

“It will come down to the industry itself to deal with it.”

Modern farming practices including wintering off and grazing young stock off home properties had increased the risk and susceptibility of herds to BVD infection.

Vaccination was available but farmers had also been encouraged to practice good biosecurity procedures whenever new stock went onto a farm and to ensure neighbouring stock could not enter the farm to infect a herd.

Campbell said new testing methods for viral antigens meant calves no longer had to be over 35 days old before being tested, making the job one that could easily be fitted in around other veterinary tasks like de-budding.

“We would encourage vets to talk to farmer clients about redirecting how they spend the money they have been on bulk milk sampling.

“Do we still want to be just sampling and identifying infected herd members in five to eight years’ time or would we rather divert some of that money and time to keeping them out in the first place?”

The greatest cost to farmers came from rearing a high-value replacement calf that was infected and not identifying it until she was in the milking herd, only to have to cull her.

“That cost would be into the thousands.

“And it is true that often it may be the poorest, snottiest cows in the herd that have BVD but we have also found herds with what appear to be very good cows in them that are also infected.

“We need to identify them sooner so they are not even getting into the herd in the first place.”

SVS intended to work closely with vets to help farmers focus more on BVD identification in coming months.

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