Diagnosis and control of lameness in sheep

LAMENESS in sheep is a common and persistent disease.

As sheep’s feet are exposed, lameness can occur at any time of year. Lame ewes, rams and lambs do not thrive well, and this loss in production – and the costs associated with treating lame sheep such as antibiotics, footbath solution, and so on – incurs a significant cost to sheep farmers.

The two main causes of lameness are scald and footrot. The key to controlling lameness is the proper diagnosis of lame sheep. A scald is most likely the diagnosis if there are sores between the digits at the back of the foot, no smell, and the sheep become severely lame very quickly. If the hoof horn is lifting, the hoof is rotting and foul smelling, then it is most likely footrot.

Another cause of lameness which farmers have become familiar with is Contagious Ovine Digital Dermatitis (CODD). CODD begins in lesions or ulcers in the coronary band. The infection starts small but can spread under the horn towards the toe, and in severe cases the whole horn can fall off.

As CODD can spread rapidly through the flock, a quick diagnosis is important to differentiate CODD from footrot. A veterinary surgeon should be called out to your farm to confirm a CODD diagnosis and give advice on products for treatment.

Footrot is a highly contagious disease and spreads more readily in warm, moist weather outdoors and when sheep are housed. Outbreaks of scald are typically seen in lambs on pasture and among ewes housed on straw. Wet conditions predispose interdigital skin to an outbreak of scald.

Other causes of lameness include shelly hoof, white line absess and toe granuloma.

Once diagnosis is completed, treatment should begin immediately. Scald can be treated using oxytetracycline aerosol spray or walking sheep through a 10 per cent copper sulphate solution or 3 per cent Formalin in a footbath. It usually provides effective control (allow sheep time to stand in footbath solution for a more effective treatment).

After foot bathing, allow sheep to stand in a dry area, so solution can dry into the feet.

For treatment of footrot, isolate badly affected sheep and consider paring, spraying with antibiotics or, in severe cases, a long-acting antibiotic injection. It is important to update sheep-handling facilities, as flocks with good handling/ footbathing facilities in general have far fewer problems.

Ideally, sheep should be footbathed every time they are in for handling/drafting, or if there is an outbreak of scald in young lambs’ footbath immediately. Lame sheep should be separated from the flock, put into a different paddock, footbathed every five days until they are cured, and then returned to the main flock. The aim should be to keep the number of lame sheep at any one time below five per cent.

If more than five per cent of the flock is lame, then a control plan is needed. This plan should consist of treatment (antibiotics, footbathing), avoiding the spread of footrot, or CODD, vaccination, culling and quarantine all sheep incoming to avoid the introduction of a different and perhaps more virulent strain of footrot or CODD.

Other general measures to help prevent and reduce lameness include reducing high-stocking densities in houses. This decreases your chance of damp bedding and infection spread. Ensure enough space and fresh bedding.

Farmers also find the use of lime in straw-bedded sheds effective for the treatment of lameness; however it may cause sheep to cough.

Rotational grazing ensures sheep are on clean pastures, as bacteria can survive on pastures for up to 12 days in favourable conditions.

Ensure roads and handling facilities are well maintained.

A flock-health plan should be prepared with appropriate veterinary and/or technical advice, and update annually.