December 02 2008
Rog Wood
The National Beef Association has called for a more serious approach to eradicating bovine viral diarrhoea by the livestock industry because those animals that are persistently infected may spread bluetongue, even in vaccinated herds.
According to the association, animals suffering persistent infections may not respond to bluetongue vaccination, because their immune response system has been damaged by the viral infection before birth.
Therefore, they could remain carriers of the midge-borne bluetongue virus, as well as continuing to shed the diarrhoea virus. Such animals, even though vaccinated, could infect vulnerable calves before they are old enough to be given bluetongue vaccine.
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"Over 85% of all UK beef herds have this viral infection, and most farms will perpetuate this because about 1% of their cattle will have persistent infections," said the association's chairman, Christopher Thomas Everard.
"Because of the high level of infection and a previously high cost of testing, little was done about these animals. Now, however, persistent infections can be diagnosed and removed easily and cheaply."
According to Everard, the testing and removal of persistent infections of the virus is a single capital investment in a herd and should be a once-in-a-herd-lifetime event. "In the first year, all suckling calves, cows, replacement heifers and bulls should be tested.
"As long as reasonable care is taken, only purchased animals need to be screened for persistent infections from then on. The tests cost £20 for groups of ten. Each herd's economic performance should improve markedly, resulting in savings of about £45 per suckler cow per year from reduced calf losses and fewer drugs, and up to £30 a head for store cattle after weaning, if the viral disease is no longer present."
Everard cites Orkney, with the densest population of beef cows in Europe, as an example of what can be achieved. With 28,000 cows on 100,000 hectares, 537 Orkney farmers have cooperated to identify and remove 402 animals with persistent infections and, after further testing, their herds are proven clear of the virus.
"Now Orkney herds are rearing 1500 to 2000 additional cattle a year, generating more income as a result of having fewer barren cows, fewer abortions and better thriving animals. And, should it ever become a problem to them, they have also increased their protection against bluetongue," Everard added.
Nigel Miller, NFU Scotland vice-president and a qualified vet, agrees that eradicating this viral disease would be a real benefit for everyone in the industry, but reckons the bluetongue issue is "a bit of a side show".
He said: "There are several entirely good reasons to eradicate this viral disease, but to mix them up with bluetongue is a bit convoluted."
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