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Lameness in sheep is one of the main welfare problems in the UK sheep population. It can also be well managed by following simple preventative and treatment measures. Lameness can cause huge welfare and economical problems in flock: an animal in pain will spend less time feeding and grazing and more time lying down with decrease in body condition, lower lambing percentages, reduced growth rates in lambs, poor fertility in rams and many more.
Some of the more common causes of lameness are as follows:
Scald is the most common cause of lameness in sheep and is most prevalent when conditions underfoot are wet. It can be a precursor to some other more severe causes of lameness so needs to be treated promptly. It can affect all age groups but is more prevalent in lambs than ewes. It is caused by the bacteria Fusobacterium necrophorum, which is found naturally in the environment. It is commonly spread in warm, damp conditions during grazing periods. Skin in between the claws is affected. It becomes swollen, sore and inflamed and covered by a thin layer of white material There is no under-running of the hoof wall and no foul smell although sheep can appear quite lame with this condition.
Individual cases of scald can be treated topically using oxytetracycline aerosol sprays. When several animals are affected, walking sheep through a 10% zinc sulphate solution or 3% formalin in a footbath usually provides effective control. It is usually necessary to repeat the foot bathing at weekly intervals throughout the risk period. Afterwards foot bathing sheep must stand in a dry area so that the formalin or zinc sulphate can dry on the feet. At concentrations greater than 5%, formalin can cause severe irritation of the interdigital skin.
Footrot is very common condition, it is extremely painful and very contagious. Animals will often be found carrying the affected leg or will be recumbent for long periods of time. If both front feet are affected, animals will walk on their knees. It causes rapid loss of body condition. It is caused by two different types of bacteria- Dichelobacter nodusus and Fusobacterium necrophorum. The first sign of footrot is swelling and moistening of the inter-digital skin. A break occurs at the skin horn junction from where infection spreads under the horn tissue so that the wall of the hoof becomes separated and the sole under-run. Wet conditions soften the inter-digital space making it more susceptible to bacterial penetration. Housed sheep are also at risk from damp, warm bedding. Affected feet have a very characteristic foul smell. In chronic cases, the hoof walls and toes become overgrown and misshapen, trapping dirt and inflammatory exudate between the inflamed, granulating soft tissues of the sole and overgrown horn. Affected feet may be fly-struck.
Peaks occur normally between April and June then again later between August and October in the UK. Rotational grazing and isolating those animals with the disease can help to control as the bacteria can survive off the foot for up to 12 days.
This is an apparently new disease in which sheep are extremely lame and a large proportion of the flock can be affected. The lesion begins at the coronary band of the hoof and runs downwards towards the toe often resulting in the loss of the whole hoof capsule. The foot is often so badly damaged that the horn does not grow back properly. There is usually hair loss for 2-3cm above the coronary band and there is no inter-digital involvement. The condition is not well understood, but it is believed that different kinds of bacteria may be involved including possibly a spirochaete similar to that which causes digital dermatitis in cattle.
Control depends on purchasing all sheep from known sources and/or health status to reduce the risk of infection, isolation of all purchased sheep for at least 30 days, regular inspection of all purchased sheep during the quarantine period, and the isolation of any sheep found to be lame and prompt treatment with a suitable antibiotic recommended by your veterinary surgeon.
Tilmicosin (Micotil) is often found to be more effective than oxytetracycline during the acute phase of CODD. Veterinary administration of tilmicosin should ensure accurate diagnosis of CODD on clinical examination but it is equally effective, although more expensive, for virulent footrot.
No antibiotic is licensed for use in footbaths but lincomycin and tylosin have been used.