Infections picked up in summer, rather than reduced efficacy of treatments, are largely responsible for the increase in herds reporting lameness caused by digital dermatitis this winter.
Stroud, Glos-based vet Chris Watson of the Wood Vet Group says some herd managers are saying their existing treatments are failing, but in cases he’s seen it is simply that control measures need better implementation.
“Unless treatment is carried out correctly, its success will be limited and infection will continue to spread.”
It is vital to clean feet properly before applying treatments, he says.
“Otherwise chemicals will make insufficient contact with the infection and cases will continue to develop.
“The most common form of treatment is a formalin footbath, but unless it is mixed at the correct rate its effectiveness will be compromised.”
To be effective, he advises a 2.5-5% concentration.
“So long as it is used regularly – preferably five days out of seven – and the solution is changed regularly then a lower concentration can be effective.”
Wilts-based vet Keith Cutler adds that formalin has been used successfully at about 10-12% concentration on some farms.
“But this is only for controlling infection, it should never be used at that strength when treating lesions.
It would do more harm than good.”
When treating individual cases, Mr Cutler advises treatment with an antibiotic spray.
But feet must be thoroughly cleaned first and then dried before spraying them.
“I tend to spray them once then hold the foot up for a minute until the spray has dried and then treat it again before putting the foot back down.”
The key to limiting the effects of digital dermatitis is to keep cows’ feet as clean as possible, says Mr Watson.
This means keeping housing clean and ensuring slurry scraping is done effectively, as the organism is spread in slurry.
Mr Cutler suggests rapid expansions on dairy farms could also be partly to blame for increasing infection rates.
“More cattle are being kept in existing accommodation, increasing stocking rates.
This means there is more slurry around cows’ feet, increasing the risk of infection.”
When considering cattle stocking densities, Wilts-based Andrew Norton says it is better to think in terms of bodyweight/sq m rather than cattle numbers.
“Dairy cows have increased in size dramatically over the last 10-15 years, but much housing hasn’t been adjusted to cope with this. Bigger cows will produce more slurry, so the increased digital dermatitis risk this poses must be taken into account.”
However, no matter what farmers do to limit its spread, it is unlikely that digital dermatitis will ever be eradicated from a herd once its there.
“The key is to keep on top of it,” adds Mr Watson.
But it’s important to correctly diagnose lameness problems, says Cheshire-based Neil Howie.
“Be on the lookout for superfowl, a combination of fowl of the foot and digital dermatitis.
This needs treating hard and quickly, often with anti-inflammatory drugs and an antibiotic.”