Since implementing an IBR vaccination programme last spring, one block calving system has witnessed almost instant improvements in milk production and fertility rates, reports Aly Balsom.
In a spring block calving system, the effects of higher return rates can be far reaching, leading to grassland management challenges, higher costs and fertility headaches the following season.
Contract herdsman, Merv Baker has witnessed the effects first hand at Court House Dairy, near Sherborne, Dorset, where he manages the 300-cow, organic herd. Up until this season – when an IBR vaccination policy was implemented – abortion had been a ‘niggling problem’ for some time, which was having a detrimental effect on calving pattern.
Mr Baker explains: “It meant more were calving at the end of the block. Those at the end of the block are the ones you have problems with as they take longer to clean up. If they calve at the front, they have more time to come cycling and you tend to get stronger bulling.”
Reduced stocking rates at the start of the grazing season also meant there was a risk of grass getting ahead of the herd, leading to grazing quality issues.
“The idea is they should milk as efficiently as possible off grass as they can and you need a tight calving block to get them out as soon as you can and get as much milk as you can off an early bite. That’s the cheapest way to produce milk,” adds Mr Baker.
With this in mind, vet Jenny Bellini, of Friars Moor Vets, decided to look into possible disease challenge on farm. The farm team had already been vaccinating for BVD for about three years, so attention was turned to Infectious Bovine Rhinotracheitis (IBR).
IBR can cause embryonic losses, milk loss and general fertility issues and can be spread by nasal and ocular discharge, typically from cow to cow. This makes shared fence lines a potential risk area. There is also some concern it can be transferred via shared cattle trailers and machinery.
The fact the herd is not fully closed creates some risk of IBR spread. The business includes a number of spring and autumn block calving herds, so although Court House Dairy does produce its own replacements, on some occasions heifers can move between farms.
Ms Bellini adds: “IBR status on those farms is unknown or positive, so I knew they posed a risk. In the South West it is also very rare to have a herd without IBR, unless it’s a truly closed herd that has been closed for some time. I’d say all farms are at risk of IBR and should be testing if they are not vaccinating.”
In the spring of last year, the farm took advantage of a subsidised bulk milk test for IBR available through MSD Animal Health. This test looks for IBR antibodies which are an indication of IBR exposure. The results came back positive, which demonstrated that vaccination would be beneficial, although vaccination should be considered in negative herds at risk of IBR to help maintain their status.
Ms Bellini says: “In a non-vaccinated herd, you should test bulk milk quarterly for antibodies. Because the test is subsidised, there’s nothing to lose. If you have a high positive result on your bulk milk test, there are merits in vaccinating, even if you don’t see any clinical signs.”
Clinical signs of the disease can include streaming noses and eyes. However, subclinical signs such as sub-optimal fertility and milk drop are more common.
“People often forget about subclinical disease. The cost can be huge in terms of fertility, milk yield and cow health. If cows are infected with IBR they are also immunosuppressed so they are more likely to get other diseases,” adds Ms Bellini.
A recent farm study carried out by vet Jonathan Statham from Bishopton Veterinary Group highlighted the substantial impact of the disease on production. The trial found cows infected with IBR gave an average 2.6kg less milk a cow a day, versus cows that did not have IBR antibodies.
To protect the herd at Court House Dairy against further effects of the disease, Ms Bellini designed a herd vaccination programme to incorporate IBR vaccination with the current BVD vaccination protocol. Vaccination would reduce shedding of the IBR virus from infected animals to reduce disease challenge and also help protect uninfected animals.
The Bovilis IBR Marker live vaccine booster was given to all breeding animals in combination with Bovilis BVD vaccine in February. This would ensure animals were fully covered before service began in May. Another dose of the IBR vaccine was then given six months later in August.
Mr Baker says the benefi ts of controlling IBR were immediately clear to see in the Holstein-Friesian and Holstein-Friesian cross Ayrshire herd.
“We got quite a few more in calf. More held to fi rst service than normal. We have a certain amount of straws allocated and there were a lot of straws left over. I reckon 70% held to fi rst service. We should have more at the front end of the calving block this spring,” he says.
Records show the farm averaged 1.4 AI straws per cow this year, versus 1.8 straws per cow last year. Mr Baker also believes milk yields have been better this season, which can partly be put down put down to IBR vaccination, as well as a good spring.
“Cows defi nitely started better and maintained yields for longer. By this time last year (November 21) we had 30 dry and we’ve only got 10-12 dry now, so they’re still going,” he says.
Milk yield fi gures show cows produced an average 6,691 litres a cow a year this year, versus 6,104 litres last year, pre-vaccination, despite little changes to management.
Moving forward, the farm will continue to vaccinate for IBR, together with BVD. BVD can also cause reduced fertility through high levels of abortion and returns, so controlling both is a must.
Ms Bellini also undertakes quarterly bulk milk testing for BVD virus to identify if there is a persistently infected (PI) animal in the herd.
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. Identifying and culling these PI animals is a crucial part of any BVD control strategy. Last year, the bulk test came back positive so all heifers that had just joined the herd were tested. This identifi ed a bought-in PI animal which was then culled, along with her calf.
Ms Bellini says it is still important to hunt out PIs, even when a herd is vaccinated. “If you do everything right and there are no PIs, the vaccine is effective. If there are PIs, they will continue to be PIs even if vaccinated, and must be culled as soon as possible. Vaccination is important to help protect the rest of the herd.”
All beef calves are also tag and tested for BVD before sale. This method of testing uses a specialist ear tag that automatically takes a tissue sample which is then tested to see if the calf is a PI. Ms Bellini says in an ideal world, heifer calves would be tag and tested too.
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:email@example.com W: www.msd-animal-health.co.uk