16 February 1996

ROT NOT ONLY FOOT SNAG

As on-farm welfare considerations increase, tackling flock lameness should move to the top of producers lists of priorities. Jeremy Hunt reports the latest research, highlighting major conditions with their treatments outlined alongside

FOOT ROT may not be the only important cause of lameness in sheep flocks, according to work undertaken by leading sheep vet Dr Agnes Winter of Liverpool University.

She is concerned many farmers are treating all lame sheep as foot rot cases when this may not be the correct diagnosis and treatment therefore inappropriate.

"I have inspected flocks where the farmer has been tackling lameness with standard foot rot treatments and not achieving any improvement," says Dr Winter. "In fact the incidence of foot rot has been quite low in these cases but the other conditions present, which have been responsible for the lameness, have not responded to normal foot rot controls."

One of the main areas of confusion, and something that is often mistaken for foot rot, is a condition affecting the white-line of the hoof – the area where the horn joins the sole – known as shelly-hoof.

This is caused by separation of the hoof from the underlying structure along the white-line leaving a "pocket" which then becomes impacted with soil.

"Its best to pare the loose horn away to leave a half-moon shape in the hoof wall. Any soil impacted should be removed taking great care not to delve too deeply into the hoof itself," says Dr Winter. "If this condition is left the soil will track up into the higher part of the foot causing an abscess in the hoof and lameness."

If the condition is identified before it becomes too advanced and treated as part of routine foot trimming there should be no serious consequences. If neglected it is likely an abscess may form which will burst out at the top of the hoof. Dr Winter recommends a poultice treatment should be applied to the top part of the foot and left for three days, if necessary.

Another condition occurring on the white-line area of the hoof has been identified by Dr Winter and is referred to as a white-line abscess. This will cause acute lameness but can be extremely difficult to detect. The foot appears free of any clinical infection or physical problem and yet the sheep is very lame and will show signs of pain if pressure is applied to the affected digit.

The cause in this case is not fully apparent until the sole is carefully pared to reveal the white-line which may well contain a tiny black or discoloured mark. This is the clinical sign of infection running deep into the upper part of the foot. If the mark is pared, pus may be released.

"We arent sure what causes this but it can affect a significant percentage of a flock. It is possible it is linked to changes which take place in the horn when ewes are fed higher levels of concentrates before lambing but this is pure speculation," says Dr Winter who suggests the infection can be treated with a poultice if necessary.

Aggressive paring of over-grown feet, especially at the toe, causes bleeding and may lead to the formation of a granuloma. This fleshy, strawberry-like growth will never heal, although new horn growth will hide it. The only corrective treatment is to have the granuloma surgically removed under anaesthetic.

Dr Winter believes foot trimming standards are improving but recalls a time when farmers were advised to "trim until they bleed and expose the infection."

"That is not necessary and thankfully many farmers now realise that to pare feet to that degree is totally unacceptable and doing more harm than good," she says. "Its best to trim until you can reach a diagnosis and then treat it. Dont work on the theory that excessive exposure of the infected area to air will rectify the problem."

An abscess forming in the pedal joint of the foot can also cause severe prolonged lameness and is most often seen in mature, heavyweight rams. It is thought to be caused by infection spreading through the thin area of skin between the cleft and the pedal joint. The claw is swollen and very painful if manipulated and pus can appear from several sites. Amputation of the infected claw

is often the most effective

and successful treatment.

One of the most common causes of foot problems in sheep is scald. "This may well lead into foot rot if the foot rot bugs are present but scald can be difficult to deal with. Most foot bath treatments will work but may only be effective for a short time," advises Dr Winter.

But more fundamental causes of lameness can often be identified. Lumps of soil which become trapped and compacted between the clefts of the hoof can start to rub and irritate the skin and lead to scald. Lame sheep should be checked for this problem and the irritant removed. The lameness may recur and there is no way of preventing it.

Less common conditions which have been identified in the hoof include interdigital fibroma which is an outgrowth of skin in the cleft. This grows and rubs and, though it may be tolerated in young sheep, the larger fibroma in older sheep can be painful. This is a genetic problem so consideration should be given to culling persistent offenders. The only treatment for the fibroma is removal of the outgrowth by a vet.

Foot rot remains one of the major causes of lameness and always starts in the cleft area of the hoof with scald-type lesions. The infection spreads and invades to the horn which lifts and separates starting from the heel.

"Farmers can greatly reduce the incidence of lameness by being fully conversant with the full range of problems affecting sheeps feet and treating appropriately," says Dr Winter. &#42

A granuloma is a fleshy, strawberry-like growth which will never heal, although new horn growth will hide it. The only corrective treatment is

to have the granuloma surgically removed under anaesthetic.

Major conditions responsible for lameness

&#8226 Foot rot: major cause. Starts in the cleft area with scald-type lesions. Infection invades the horn which lifts and separates from the heel.

&#8226 Shelly-hoof: affects the white line. Often mistaken for foot rot. If neglected abscesses will burst from top of hoof.

&#8226 White-line abscess: Causes acute lameness, but is difficult to detect. Foot appears free from clinical infection or physical problem, yet sheep shows signs of pain when pressure applied to affected digit.

&#8226 Granuloma: result of aggressive over-paring. Fleshy, strawberry-like growth which never heals.

&#8226 Abscess in pedal joint: often seen in mature heavyweight rams. Amputation of infected claw often most effective and successful treatment.

&#8226 Scald: can lead to foot rot if two specific bacteria present. Most foot bath treatments work, but may only be effective for short period.

Scald can lead to foot rot when two specific bacteria share the same environment. The latter condition (pictured above) remains one of the major causes of lameness.

A case of severe foot-rot. Infection starts in the cleft area of the hoof with scald-type lesions. If left untreated, it then spreads and invades the horn which lifts and separates starting at the heel.

Shelly-hoof is often mistaken for foot rot. It affects the hoofs white line. Best treatment is paring away loose horn to leave a half-moon shape in the hoof wall.

Pedal abscesses are most often seen in mature heavy-weight rams. Amputation of the infected claw is currently the most effective and successful treatment.

Lumps of soil which become trapped and compacted between the clefts of the hoof can start to rub and irritate the skin, leading to scald.