17 April 2019
A custom-made vaccine in combination with herd management changes are helping a Carmarthenshire dairy farm protect calves against a disease that was responsible for deaths in large numbers of its heifer replacements.
Since 2015, David and Eirian Thomas had experienced a high level of calf mortalities at Wern Farm, a Farming Connect Focus Site near Bancyfelin.
“The calves were fine when they were born but at any time from two days to two months they would get ill, often with the symptoms of pneumonia, but they wouldn’t respond to antibiotics,’’ Mr Thomas recalls.
“These were big strong calves; they were absolutely fine one day then dead the next.’’
Working with their vet David Staak, of the Market Hall Veterinary Practice, St Clears, they eventually linked the deaths to Mycoplasma bovis (M bovis), a highly contagious bacterium that is a major contributor to calf pneumonia and is also associated with meningitis, eye and ear infections as well as arthritis, mastitis, abortion and infertility in adult cows.
M bovis has no cell walls so doesn’t respond to many antibiotics but an autogenous vaccine, given to dry cows and subsequently to their calves, offered the Thomas’s an opportunity to protect their herd from this devastating disease.
They hosted a Farming Connect trial which involved creating a vaccine and inoculating the herd.
To create a vaccine, swabs can be taken from a calf’s nose or direct from lung tissue of dead animals. The vaccine is farm-specific so is only effective on the source farm.
Cows at Wern Farm were vaccinated at six weeks and three weeks pre-calving to allow a passive transfer of immunity to their calves. Calves were then given the vaccine at two weeks and four weeks old.
Calf deaths from birth to weaning in January had been 63% but the first of the vaccinated cows calved on February 10th and mortalities in February dropped to 32% with most of these caused by scours.
Mr Staak says the early signs are encouraging. “It is early days and I don’t want farmers to think that vaccinating is a silver bullet for M bovis but it does seem to be working.’’
He advises that vaccination should not be used in isolation – herd management also plays a key role in protecting cows and calves from M bovis.
Five hundred doses of the vaccine – sufficient to protect 125 calves – were produced for the trial at Wern Farm at a cost of £7.50/dose, which worked out at £30 to protect one calf.
The more vaccines a farm purchases, the lower the cost per dose as is the case when a farm re-orders the vaccine in subsequent years, says Mr Staak. “The lab holds the samples from the farm indefinitely to regrow the vaccine when required,’’ he says.
Mr Staak says it was important to consider other causes of calf mortality before embarking on a vaccination programme.
“It is important to rule out other causes because you could spend money on vaccinating for M bovis but continue to get pneumonia from another source.’’
The Thomas’s admit the cost of vaccination is a consideration but that it was economically viable in their situation.
“We have lost a lot of cows to TB in the last 18 months so heifer replacements are very important,’’ says Mr Thomas.
“It is a big relief to be getting on top of the problem, it was heartbreaking to see so many calves dying.’’
Mr Staak believes TB is indirectly responsible for the rise in the number of cases of M bovis in Welsh herds because more farmers are buying in cattle – and disease – to replace slaughtered animals.
Once M bovis is in the herd it is very difficult to control, he says. It spreads from calf to calf through direct contact and through colostrum and whole milk.
Farming Connect supported the trial because of growing levels of M bovis infection in Welsh herds and a need to understand more about this disease.
Abigail James, Farming Connect South West Wales Dairy Technical Officer, says the condition is often misdiagnosed as pneumonia or joint ill so many farmers are unaware they have M bovis.
Funding for the project was provided by the Welsh Government’s Rural Communities Rural Development Programme 2014-2020.
Farming Connect, in conjunction with AHDB, held an open day at Wern Farm to share the trial findings with other farmers.
Mr and Mrs Thomas run a 300-cow herd with cows milked by five robotic milkers installed three years ago.
In addition to vaccination, a number of other changes have been put in place to tackle M bovis in the housed herd at Wern Farm.
There is now a dedicated calf rearing area – calves were previously housed in a section of a building used for cows on the point of calving – and improvements have been made to colostrum management.
Changes have also been made to the dry cow diet – instead of running the dry cows as one group there is now a close-to-calving group where cows receive 2.5kg of dry cow blend in combination with silage and chopped straw for three weeks pre-calving.
Symptoms of M. bovis in calves include a high temperature, nasal discharge, coughing and ear droop/head tilt caused by middle ear infection. In cows, it mostly presents as arthritis (swollen joints), mastitis and reproductive issues.
Sub clinically infected animals risk spreading infection through the herd.
In New Zealand, the government is taking a tough approach to controlling M bovis by slaughtering tens of thousands of cows and that culling programme is continuing.