Over-trimming can be worse than rot
By Jonathan Riley
OVER-TRIMMING of sheeps feet represents more of a welfare problem than foot-rot itself, says David Henderson, head of the Moredun Foundations farm and clinical studies division.
"Lameness in sheep is a very obvious ailment raising its profile in terms of animal welfare. Foot-rot is an infectious disease but is frequently not treated as such," Dr Henderson told a meeting of sheep farmers in Kent.
Air temperatures over 10C (50F) enable the disease to spread when combined with long periods of wet weather. On wet grass the skin between the animals cloves can become denatured exposing it to infection. In housed sheep wet straw beneath the surface layer can heat up to 10C providing an excellent medium for bugs to survive and infect feet.
The first organism to invade causes scald of the foot, which can be cured usually by foot bathing.
Footrot itself is caused by more aggressive organisms which eat away the sole of the foot leading to separation of the horn on the outside.
"Four treatment methods can be used in conjunction with each other if necessary – paring, bathing, antibiotics and vaccination. The most virulent types need a combination of the four," he said.
"When sheep are not wearing feet down, paring is necessary. But over-trimming leaves the foot open to infection, abscesses and other serious lesions."
Dr Henderson advised that foot-bathing should be carried out on a dry day otherwise the treatment would be less effective. And that zinc sulphate at 10% should be used rather than formalin.
"Wash feet in a water-bath before sheep enter the zinc sulphate bath and keep them standing for at least 5-10 minutes, although the longer the better. When there is a severe case of foot-rot dont pare the foot until antibiotics have been used," he warned.
Australian research has shown that penicillin plus streptomycin administered in one large dose produced the best results. "Seek advice from your vet on the dose required for your sheep. As an example 10-12ml given to a Mule should cure 95% of foot-rot in a week.
"Any not responding to the treatment should be sold off as quickly as possible or they will reinfect the flock.
"When a virulent form of foot-rot is present vaccination is advisable because it has a curative effect as well as helping to prevent further spread.
"Once under control judicious paring can then take place leaving a wall of horn around the foot to protect and keep clean the softer tissue beneath," he said.
"Over-trimming leaves the foot open to infection, abscesses and other serious lesions," says Dr David Henderson.
Rather than alleviate the problem of foot-rot over-zealous trimming has caused this sheeps foot to bleed, exposing it to risk of further infection.