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Foot Trimming of Sheep

Background

Data suggests that at least 10 per cent of the national flock in the UK is lame at any one moment equivalent to about 3 million sheep. In well-managed flocks the prevalence of lameness can be as low as 2 per cent and this figure represents an achievable target in most situations.

Responsibilities

There is a large amount of legislation detailing the necessity for daily inspection of intensively-managed sheep (lowground and upland farms) and their prompt and correct care and treatment.  Farmers must be familiar with the Code of Recommendations for the Welfare of Livestock - Sheep (2002).  Other regulations include The Welfare of Farmed Animals Regulations (2007).

Summary

Foot trimming was once regarded an essential component of treating all causes of lameness in sheep and an important skill for all shepherds learn. It is a skill that has been used extensively as a method of controlling lameness in sheep. Recent work has shown that, although a useful skill, it has been over used and in cases of an infected foot due to footrot or interdigital dermatitis, it is counter productive causing a more severe lameness, with a slower rate of healing.

Annual foot inspection is to be recommended but trimming should only be undertaken in a minority of cases. The purpose of trimming is to remove overgrown horn, leaving sufficient wall to take the weight of the sheep. The corium should not be exposed nor should bleeding be an outcome. While foot trimming is still essential to correctly locate and drain a foot abscess, recent research work has shown that foot trimming is counter-productive in cases of footrot.

Most outbreaks of lameness in sheep are caused by either interdigital dermatitis (scald) or footrot. Footrot is responsible for 90 per cent of sheep lameness.  Important recent developments in the treatment of footrot detail the importance of prompt parenteral antibiotic treatment and no foot trimming either as a curative or preventive procedure. The majority of cases of lameness in sheep do not require foot trimming; indeed, foot trimming in sheep with footrot may further damage the corium such that healing is delayed and the sheep is lame for longer.

Farmers should consult their veterinary surgeon for specific advice on the correct course of treatment for lame sheep on their farm.

fig1

Overgrown hooves result from failure of normal weight-bearing caused by lameness.  Treat lame sheep the same day they become lame and the hoof horn will not become overgrown.

fig2

Closer view of the overgrown front feet of the ram pictured above.

fig3

These hooves do not need to be trimmed.

fig4

Foot trimming in this case of footrot would have caused acute pain to the sheep and has achieved little.  Indeed, healing may be delayed as a consequence of potential further damage to the corium during foot trimming.

As a general rule, if there are signs of an obvious infection, then that should be treated before any trimming is undertaken

Veterinary attention is essential for the correct diagnosis and treatment of contagious ovine digital dermatitis (CODD).

Common causes of lameness

Most outbreaks of lameness in sheep are caused by either interdigital dermatitis (scald) or footrot.  Interdigital dermatitis and footrot are caused by the bacterium Dichelobacter nodosus.  The UK's temperate climate provides an ideal environment for transmission of the bacterium that causes footrot.  The important risk factors for foot lameness are damage to the interdigital skin by exposure to moisture and mechanical trauma, and transmission of D. nodosus from infected sheep. Other risk factors include sale and movement of sheep and a lack of effective biosecurity.

Interdigital dermatitis

fig5

Many outbreaks of lameness in lambs are caused by interdigital dermatitis.

Interdigital dermatitis is the most common cause of lameness in lambs and occurs most commonly when underfoot conditions are wet often in late spring. At grass, the prevalence is generally greater in lambs than in ewes, but interdigital dermatitis can become problematic in housed ewes, when straw bedding becomes wet and warm.

The interdigital skin is red and swollen and covered by a thin layer of white material. There is no under-running of the hoof wall or sole.

fig6

Scald: the interdigital skin is red and swollen and covered by a thin layer of white exudate.

Individual cases of interdigital dermatitis can be treated topically using oxytetracycline aerosol sprays.  When several animals are affected, treating all sheep in the group in a 10% zinc sulphate solution or 3% formalin in a footbath usually provides effective control. After footbathing, sheep must stand in a dry area so that the formalin or zinc sulphate can dry on the feet. It is usually necessary to repeat the foot bathing at weekly or two weekly intervals throughout the risk period to prevent disease transmission and more lame sheep. No foot trimming is necessary.

Footbathing is most successful in treating interdigital dermatitis in lambs and preventing footrot. There is no scientific evidence that any one type of bath treatment formulation is more effective than another.  At concentrations greater than 5%, formalin can cause severe irritation of the interdigital skin.  The practice of regularly replenishing footbaths with a few splashes of concentrated formalin solution should be avoided.

Footrot

Footrot is an extremely painful disease and affected animals can lose weight rapidly. Sheep with footrot are very lame, remain recumbent for long periods and may not bear weight on the affected leg.  When both forelimbs are affected, sheep walk on their knees.  There is swelling and moistening of the interdigital skin with infection spreading to separate the horn tissue of the sole from the corium and extend up the wall in neglected cases.  There is a characteristic foul-smelling discharge.

fig7

Footrot causing severe lameness in all three Blueface Leicester rams in this group.

fig8

Early case of footrot with infection spreading under the horn tissue so that horn becomes separated from the sole.  This foot must not be trimmed.

fig9

Footrot where infection has spread under the horn tissue of the sole.  The reddened corium has become exposed causing pain. This foot must not be trimmed.

fig10

Advanced footrot under-running the sole and extending to the hoof wall. This hoof must not be trimmed.

In chronic cases, the hoof walls and toes become overgrown and mis-shapen, trapping dirt and inflammatory exudate between the inflamed, granulating soft tissues of the sole and overgrown horn. Such cases should be treated with an injection of long acting antibiotic (10 mg/kg of oxytetracycline) together with removal of all debris from the interdigital space and application of an antibacterial spray.  Affected sheep must be isolated with other sheep undergoing similar treatment.  The grossly overgrown horn should be trimmed with sharp foot shears after about one week when the footrot lesion is much less inflamed.  Only grossly overgrown flaps of horn which could trap dirt should be removed.

fig11

The hoof walls and toes become grossly overgrown and mis-shapen,

fig13

A neglected case of footrot where the hoof wall has become overgrown and mis-shapen.  Excess flaps of horn can be trimmed once the foot is much less inflamed.

fig14

Neglected case of footrot - this must not happen.  Only large loose flaps of horn should be removed with sharp hoof shears after antibiotic treatment.

The best current treatment for footrot is an injection of long acting antibiotic (e.g., 10 mg/kg of oxytetracycline injected intramuscularly), together with removal of any debris from the interdigital space and use of an antibacterial spray.  Most sheep recover from lameness within a few days, a few may take up to 10 days and lesions heal over a similar period. Paring the hoof horn to expose the lesion exposes the corium, which is a sensitive tissue. This delays healing and is not recommended.  Foot paring may be undertaken when the sheep is no longer lame and the foot is grossly overgrown.  However, it must be recognised that the foot has become overgrown because the sheep has not been weight-bearing on that foot as it has previously been lame (neglected) for several weeks or more.

fig15

Foot trimming has no role in the treatment of footrot nor should it be considered as a preventive method.  Excessive trimming of the wall in this case causes most of the weight to be carried by sole which is not normal.

White line abscesses

Abscess formation arises following bacterial entry into the white line area, commonly at the toe, which may extend to discharge at the coronary band. Foot paring releases pus with removal of the under-run horn.  The corium must not be exposed as this results in delayed healing and may result in granuloma formation.

figure16

Toe abscess - pus released after careful paring.  Note the there is no damage to the corium and no bleeding.

figure17

Hoof trimming exposing an abscess which has under-run the hoof wall. Note that careful paring of the foot has caused no bleeding.  Dirt trapped in the white line has led to abscess formation which is only corrected by careful foot paring but only when there is no footrot present.

Some farmers do not trim hooves correctly and such sheep are more likely to become lame.  Cutting into sensitive tissue and causing the foot to bleed is a poor technique, causing pain, lameness, and reduced growth/weight loss.

figure18

Cutting into sensitive tissue and causing the foot to bleed is a poor technique, causing pain, susceptibility to granuloma, and infection.

Toe Fibroma/granuloma

Toe fibromas most commonly result from overzealous foot paring with exposure of the corium and excessive use of formalin footbaths.  Toe fibromas can occur in association with footrot where under-running of hoof horn exposes the corium.  This condition can be resolved by careful foot paring with excision of the growth and application of a pressure bandage to the affected area.

figure19

Toe fibromas most commonly result from overzealous foot paring with exposure of the corium and excessive use of formalin footbaths

Contagious ovine digital dermatitis (CODD)

Contagious ovine digital dermatitis (CODD) is an apparently new, severe condition first described in 1997. The characteristic clinical picture is a primary lesion at the coronary band of the outer wall with
subsequent invasion and under-running of the hoof wall from the coronary band towards the toe causing detachment then shedding of the horn capsule.  Sheep show severe lameness affecting one digit of one foot in most animals but both digits of one foot in some sheep. The damage to the corium may be so severe that re-growth of the horn is permanently affected. Typically, there is also loss of hair extending 3-5 cm above the coronary band.  There is no interdigital skin involvement.

figure20

Under-running of the hoof wall from the coronary band towards the toe causing detachment then shedding of the horn capsule in this case of CODD.  This foot must not be trimmed; veterinary advice is essential.
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