For Cheshire beef suckler producer Nigel Potts, poor growth rates in some calves – highlighted by dramatic variation in performance across groups – had become an unacceptable drain on profitability for his 160-cow enterprise.
AS well as poor growth rates in some calves, Nigel Potts, who farms at Mount Farm, near Macclesfield, was also seeing periodic abortions among his herd as well as other fertility issues, such as heifers apparently not holding to service.
The situation was frustrating, because Mr Potts had always worked hard at maintaining good health status in his herd, and it was a surprise when the farm’s vet Hollie Dale of Wright and Morten, near Macclesfield, suggested bovine viral diarrhoea (BVD) might be at the root of his problems.
Mr Potts says: “We maintain a lot of the good herd health habits we applied as dairy farmers before going out of milk 10 years ago and this includes vaccinating against BVD and leptospirosis.
“We also run what is essentially a closed herd, with bulls being the only stock coming in from outside, so I think our biosecurity is pretty good.
“I was not initially convinced we could have had a major infectious disease problem, but it was clear something was not right and blood testing was available through our vet which enabled us to check the herd’s status.”
Blood samples were initially taken from unvaccinated heifers by Ms Dale, and the results from this were the first step in establishing the root cause of problems.
Ms Dale says: “We started with a group of heifers which were not holding to natural service, checking five of the animals for evidence of exposure to the BVD virus.
“Several heifers were positive for BVD, so we then tested another group of nine-month-old heifers and found some of these also to be positive for BVD. It was clear the disease was circulating in the herd.
“When we investigated the vaccination procedure on the farm, it became clear heifers were at times not being vaccinated before bulling, and hence they were at risk of creating persistently infected [PI] calves if they became infected with the virus in early pregnancy.”
This situation at Mount Farm provides a classic example of how infection can circulate and present problems, despite vaccination taking place. It is also an illustration of how the first step must be to remove PIs before a vaccination programme can be effective.
Ms Dale says: “Once we had established BVD was present, the next important step was to identify and remove all PIs.
“In an ideal world we would test every animal and remove anything which is confirmed as a PI, but economics and practicalities come into play so a strategy has been put in place to minimise short-term risks and ultimately eliminate the disease.”
The strategy involves the use of eartag tissue sampling, which enables a sample to be taken as the eartag is attached to the calf, with the sealed capsule containing the sample then being sent away for laboratory analysis. This system is central to a new scheme which is being widely promoted by XLVets, a nationwide organisation of 53 vet practices, including Wright and Morten among its members.
Called BVD Check Tag and supported by MSD Animal Health, the scheme aims to promote the testing of calves and provide verification of a negative test result for the disease through a central and fully accessible online database.
Significantly, the scheme includes the use of branded white tags as part of the testing procedure in order to provide an easily identifiable and highly visible prompt for calf buyers to check test results before purchase.
As Ms Dale explains, the scheme has value within a specific herd and also more widely to help prevent the spread of BVD.
She says: “By identifying PIs, ideally shortly after birth and certainly before they move from their home unit, we can minimise the spread of BVD and offer more targeted control programmes in herds identified as infected.
“In the case of Mr Potts’ herd, we are using the eartag tissue testing as a crucial part of control and eradication. If the calves are clear, so are their mothers. We are blood testing all bulling heifers before they are served and screening any cows which do not calve.
“This strategy, together with correctly applied vaccination protocols and vigilant biosecurity, provides the best protection we can achieve against BVD.
“It is important to be clear of PIs and stick firmly to the correct vaccination procedures. Other factors also play a part, such as good data recording, tight calving patterns and applying best practice in areas such as biosecurity and farm hygiene.”
For Mr Potts, working closely with his vet practice has been an important catalyst for change, with the most visible benefit so far being a return to the consistently good growth rates in store cattle which have traditionally been achieved.
“Our aim is to sell weanlings in batches as they reach about 350kg liveweight,” says Mr Potts.
“In the case of better cattle, this will translate to average growth rates of about 1.2kg/head/day. If we can achieve this consistently we will maintain strong demand for our cattle, so staying free of BVD and other infectious diseases is crucial.”