Producers attending the latest meeting of the Moray and Nairn monitor farm were urged to make the most of Scottish Government subsidised BVD blood testing available until March 2011.
Scotland’s national BVD (Bovine Viral Diarrhoea) scheme was launched in September and the disease, regarded by vets as the most significant cattle disease in Europe and North America, was the main topic at the recent Moray and Nairn Monitor Farm meeting.
The meeting at Robbie Newland’s Cluny Farm near Forres, part of Quality Meat Scotland’s network of monitor farms, heard farm vet Mark Pearson of Moray Veterinary Practice, explain how BVD is spread, its impact on herd performance, how to prevent and get rid of it.
“BVD is spread by Persistently Infected cattle, known as PIs, which are born PIs. They are constant and heavy shedders of the virus and are incurable. The virus is highly contagious - if you have any PIs in your herd, the best course of action is to cull them as quickly as possible,” said Mr Pearson.
“PIs are only created in the womb - a calf cannot become a PI after it’s born. If an in-calf, naïve (un-vaccinated) female comes in contact with a PI cattle beast of any age, there is a strong risk that her foetus will be affected.
“In early to mid-pregnancy the unborn calf will be unable to mount an anti-body response to fight off the infection, and becomes a PI. Once born, if it survives, it will continue the cycle of infection. If the in-calf female is in late pregnancy, her calf may be able to fight off the infection but might be born with either deformities or brain damage.”
Farmers running closed herds may feel their cattle are safe from BVD. However, buying in bulls can pose a threat.
“If a bull comes in contact with a PI, say in a mart or in transit, he can become Transiently Infected”, explained Mark Pearson. “This would probably make him infertile for about two months, during which time he could be shedding virus in his semen.”
BVD impacts on many aspects of herd production and health, pointed out Mr Pearson, including fertility, which in turn results in fewer calves and a higher culling rate.
“A PI mingling with a group of cattle will suppress their immune system. With young stock, their susceptibility to health complications like scour and pneumonia is increased, resulting in higher mortality. With all ages of cattle, the challenge of BVD virus will result in poorer weight gain and overall performance.”
Many PIs either die before maturity, or are such conspicuously poor cattle, would not be retained for breeding but some can look perfectly healthy and will breed. If they do, they will always produce a further PI. Monitor farmer Robbie Newlands has recently discovered this.
“Thanks to screen blood testing we discovered a first calved heifer is a PI, along with her April-born calf,” Robbie told the group. “We’d bought her as an in-calf heifer, as part of a group last October, from a source which had always been reliably healthy.
“Both heifer and calf have been culled but our main concern is that last winter, the PI in-calf heifer ran with a group of around a dozen in-calf heifers, so could have infected their calves, making them PIs. All have calved, and thankfully the calves look fine, but until they’re tested we can’t be confident they’re ok.
“We’ve been aware of BVD for about ten years. We tested the herd then and all were clear. We buy in our replacements and felt that as our cows were naïve, they were vulnerable, so have been vaccinating our cows ever since.
“However we knew that buying in-calf heifers was taking a chance, and the two PIs we’ve recently found have confirmed this. So we’ve changed to buying in bulling heifers, testing them on arrival and after establishing they’re clear vaccinating them before they go to the bull.”
Vet Mark Pearson’s advised the group to make the most of the Government subsidised BVD blood testing which is available until March 2011.
“Then if BVD is found to be in your herd, identify and cull any PIs. Whether or not your cattle have BVD, start a vaccination programme. You can discuss this with your vet when he’s taking blood samples.
“The sooner you get started, the sooner you’ll be free of BVD, making your cattle and the Scottish industry healthier and more profitable,” said Mr Pearson.
The next Moray and Nairn Monitor Farm meeting will be held in the first two weeks of December.