UK - Cows with Johne’s disease give an average of 4,000 kilograms less milk over their lifetime, US data shows.
The majority of the loss comes from early culling and is a ‘conservative estimate’ in the eyes of some industry experts, National Milk Records Veterinarian Karen Bond told the Livestock Event yesterday.
She explained that the far reaching health effects of the condition make it so costly to yield.
Mrs Bond said: “Research shows that a cow with Johne’s is 1.5 times more likely to become lame, has double the chance of getting mastitis and 1.8 times more times likely to suffer digestive or respiratory disease.”
She added: “Johne’s has a big impact on lameness, mastitis and fertility – these represent the cull list on farms.”
Whether Johne’s disease cases are rising is difficult to say, according to Dr Alistair Macrae of the Dairy Heard Health and Productivity Service.
His message was that improved tests may mean farmers are more aware of the cases they had and urged regular testing, be it of blood, muck or milk to get to grips with disease presence on farm.
Once identified, Johne’s infected cows can be segregated, calved separately and kept away from any milk or colostrum pooling that may occur.
But Dr Macrae told TheDairySite that, regardless of farming system and calving strategy, Johne’s can be a problem.
“Farms that appear badly managed but have closed herds can escape because they have no route to bring the bacteria on farm,” he said.
“Contrastingly, well managed farms buying cows can be unknowingly bringing in Johne’s problems.”
This is because of a ‘triangle of factors’ which firstly requires a bacterial presence and then farm management and farm environment to allow the disease to spread, he explained.
Passing from infected dams into calves via muck, Johne’s can frequently contaminate colostrum and milk and calves.
This requires close attention of calves in the six months of life, said Dr Macrae.
The ‘biggest problem’ facing farmers is that an infected calf may not show clinical signs until the calf is three to five years old.
This means common dairy practices are a major risk factor for spreading bacteria to calves.
“Pooling colostrum is a recognised risk factor for Johne’s, as is not segregating infected cows at calving,” said Dr Macrae.
“Multiple cross suckling, feeding waste milk from cows and having group calving pens also represent a risk of transmission if a Dam is infected and not identified.”
Find out more information on Johne's disease by clicking here.