Johne’s disease affecting herds’ lifetime yields

A high incidence of Johne’s infection means many UK herds could be facing reduced lifetime yields and lower fertility, as Rhian Price reports from the DairyUK, DairyCo Johne’s conference

Between 60-70% of UK dairy herds are infected with Johne’s disease, according to Ben Bartlett, NMR business development manager.

Speaking at Sixways Stadium in Worcester last week, he explained how results from a 2011 NMR study of 710 herds, showed 73% of herds had one or more cows test positive for the disease.

“The encouraging thing is the level of infection was not that high, which suggests most people have it but it hasn’t bitten yet,” Mr Bartlett explained.

He said studies into the origin of infected animals found about 25% had been brought in.

“The risk of spreading disease is far greater than it has been in the past,” he added.

Mr Bartlett said red cows – those that frequently showed high results for Johne’s – were the most problematic and Johne’s dramatically affected the lifetime performance of these animals.

A sample of 3,950 cows tested under Herdwise in 2011 showed that average 305-day lactation yield was poorer in red cows.

In the first lactation a red cow was only giving an average of 6,500kg compared to uninfected animal giving almost 8,000kg.

Mr Bartlett said the figures were “surprising” given that the disease was not thought to impact on young animals.

Average cow lifetime yield (LTY) was also compromised in cows testing positive for the disease, with red cows yielding an average of 11kg a day of life, compared to an uninfected one averaging nearer 14kg.

“Herds languishing at the bottom of the LTY are showing much higher results of Johne’s,” said Mr Bartlett.

And further investigations conducted by the University of Reading found positive cows were nearly 50% more likely to suffer from lameness.

The university studied milk records from a total of 13,720 cows from 80 UK herds between January to March 2012 and found the disease also affected fertility.

In cows testing negative for the disease, calving to conception averaged 119 days, but in those testing positive for Johne’s calving to conception rose to 150 days.

Cows with Johne’s were also twice as likely to suffer from repeatedly high somatic cell count.

“The suspicion is that Johne’s will affect the immunity system with the cow, so she is going to be more susceptible to infections,” he added.

Mr Bartlett said the cost of the disease varied enormously depending on the level of disease on farm.

He estimated that a herd of 200, averaging 7,800kg of milk, at 30ppl could be losing £5,148 from their annual milk cheque if they had 2% clinical cows and 8% subclinical, losing yields of 15% and 10% respectively.

He added: “The cost of Johne’s is not visible to many dairy farms. However the controls do have a cost and they are visible.”

In the short-term control costs could exceed economic loss, but in the long term, when Johne’s takes hold the case for control was clear, he added.

Mr Bartlett said it was therefore vital that controls were put in place so problem cows were spotted early and culled before they impacted on herd profitability.

“By spotting them early they can be sold while they still have a cull value and you can save yourself approximately £840 a cow [in replacement and carcass removal costs],” he added.

Case study: Andrew Mycock, Derbyshire

Dairy farmer Andrew Mycock, from Buxton, Derbyshire, completely changed his management system after getting a wake-up call from a Johne’s test result.

“In December 2009 25% of the heifers showed up positive which frightened the life out of me,” Mr Mycock admitted.

Since then he has implemented protocols to control Johne’s disease more effectively in his herd of 330 cows.

Cows that test positive for the disease are given a purple tag and any red cows aren’t served again and are culled.

Once calves are born they are separated from their dam and are given two to three litres of defrosted colostrum, which is only taken from animals uninfected with Johne’s.

Furthermore all milk given to calves is pasteurised at 60C to prevent infection.

“It isn’t going to get better if you do nothing,” he stresses. “Now herd levels are fairly low and we are keeping on top of it.”