A combined approach to BVD and IBR control which involves timed vaccination, tag and testing calves and good biosecurity is proving a winning recipe for one Scottish dairy farm.
The need to calve in two distinct blocks means Dumfries and Galloway farmer, Mark Caygill, can ill afford anything which detrimentally affects fertility.With that in mind, he believes a belt and braces approach to vaccination is a must, especially considering the risk of buying in disease to his flying herd of 250 cows.
By working closely with farm vet, Will McCarthy of Galloway Veterinary Group, Mr Caygill has been able to adopt a timed vaccination policy which provides the required protection. This, along with good biosecurity and routine tag and testing of calves, puts him in a good position to ensure cows calve in their target slots.
Mr Caygill says: “We need to keep the herd as productive as we can and tools like vaccination and tag and testing help us to keep cows fertile and healthy.”
The herd calves in two blocks; one 12-week block starting in February and a new, eight-week block from July. This second block was introduced this year by buying-in 40 fresh calvers to make the most of August milk premiums. These animals were purchased instead of the usual batch of in-calf replacement heifers traditionally bought in December to calve in spring.
Moving forward, Mr Caygill is keen to do all he can to keep the two blocks distinct.
“We don’t want cows calving all summer. We need to be disciplined and cull infertile animals. We will push round some, but we’ll be strategic – they need to be giving a lot of milk,” says Mr Caygill, who farms in partnership with wife Aileen at Blue Hill Farm, Auchencairn.
To avoid the potential impact of disease on fertility, BVD and IBR have formed the main focus of infectious disease control on farm. BVD can cause reduced fertility through high levels of abortion and returns, while IBR can lead to embryonic losses and general fertility problems.
Although Scotland’s national BVD eradication scheme means regular surveillance testing for BVD is mandatory, vaccination is not a requirement of the programme. However, both Mr Caygill and Mr McCarthy believe protecting animals is essential considering replacements are coming in from numerous locations.
Mr McCarthy stresses timing of vaccination is also vital. “To ensure maximum protection from BVD infection, cattle should have their primary BVD vaccination course completed prior to service. Vaccination boosts immunity at this important time and prevents the birth of persistently infected [PI] calves.”
An unborn calf can become a PI when the dam is exposed to BVD virus during early pregnancy. The calf is unable to mount an immune response and thinks the virus is part of its body. It is then born carrying and shedding the virus.
To ensure vaccinations are timed to give the most effective protection, the spring calving group will receive their Bovilis BVD vaccine booster before service begins in May. This will be administered as part of a combined vaccine with Bovilis IBR Marker Live to save time by minimising the number of injections.
Although the aim is to buy from pre-vaccinated herds, any bought-in animals will be immediately placed on a primary vaccination programme on arrival to ensure they are covered.
Mr McCarthy adds: “Ideally you want to buy from vaccinated herds, but we would vaccinate anyway as a back up, rather than assuming vaccination had been done and timed right.”
For Mr Caygill, vaccinating the batch of fresh calved animals in July this year was a priority.
“We vaccinated with IBR and BVD vaccines as soon as they came in as our first job. It makes sense as they’re coming into contact with my cows and they’re vaccinated,” he says.
From now on, this July calving group will also get their booster as a combined BVD/IBR vaccine.
IBR vaccination is necessary as cows have shown obvious signs of the disease around housing. Continued disease pressure was also evident this season, while cows were at grass, so the vaccine was given at the start of October. Another dose will be given in spring.
Mr McCarthy says: “Once IBR is in the herd, you get latent infection and latent carriers, so you never really get rid of it. Vaccinating reduces shedding and keeps clinical disease to a minimum.”
As part of Scotland’s BVD Eradication programme, all farms also have to undertake regular surveillance testing. Mr McCarthy explains these ‘check tests’ usually involve blood testing nine to 18 month-old calves for BVD antibodies.
“This test is used to identify virus presence on farm and BVD circulation in the herd. If the test comes back negative, you can presume there is no BVD as they have never been challenged.”
Conversely, if they come back ‘not negative’, they are likely to have been exposed to BVD. Stock from these ‘not negative’ farms can only be sold direct to slaughter, unless animals are tested for BVD. Any BVD virus negative animals can then be sold live.
Because all calves at Blue Hill Farm are sold at three to four weeks of age or six to eight months old, this check test is not applicable. Therefore all calves are tag and tested within seven days of birth. This method uses a specialist ear tag which automatically takes a tissue sample which is then tested to see if the calf is a PI.
Mr McCarthy adds: “The benefi t of this is you get two generation’s results in one test as, if a cow is negative, by reason her calf is negative too. For Mark, it’s a really good way to screen what he buys in.”
This is a better way of establishing status than testing in-calf animals as a dam could test negative for BVD, but still be carrying a PI calf. Because true status of any bought-in, incalf animals and their calves cannot be known prior to calving, these animals will be kept away from the main herd at Blue Hill Farm prior to calving.
“They are then mixed at a point where BVD infection is of limited consequence as cows are about to calve and it won’t have a huge effect on the calf in the womb, and any PI would be identifi ed before breeding,” says Mr McCarthy.
Any PI animal would be culled out of the herd, although to date, no PI has been identified.
This information was provided by MSD Animal Health, makers of Bovilis® BVD, Bovilis® IBR Marker Live, Bovilis® IBR Marker Inac and Leptavoid™ H. Always use medicines responsibly. More information is available from MSD Animal Health, Walton Manor, Walton, Milton Keynes, MK7 7AJ. T: 01908 685 685 E:firstname.lastname@example.org W: www.msd-animal-health.co.uk