By Dr TB Barragry, PhD MScMVB MRCVS
LAMENESS is one of the biggest problems in sheep farming and the condition causes considerable morbidity by impacting significantly on productivity and economic returns. It is also a major animal welfare issue.
Regular and chronic lameness problems adversely affect fertility, especially conception rates in ewes, body condition score, growth, productivity, longevity, and predisposition to other diseases. It is a major negative cost factor on sheep farms in terms of production losses and costs of medication to treat the disease. In addition, the serious visual impact with welfare implications negatively impacts public perception of sheep farming.
In the UK, the farmer-estimated prevalence of lameness over a period of 10 years in English flocks was an average of 8.4 per cent and was similar a decade later at 10 per cent.
Predisposing factors and management
Deterioration of the epidermis via continuous exposure to moisture and dirt is a significant predisposing factor facilitating entry of bacteria, as well as traumatic damage and abrasion. Lack of regular, routine preventive foot bathing is also a factor, as well as poor biosecurity and/or delayed treatment of clinical cases will exacerbate the condition and facilitate the quick spread.
There is evidence to suggest inappropriate hoof trimming can increase the risk of bacterial spread and long-term hoof injury. In addition, flock owners need to be ruthless by culling persistently infected sheep to avoid a constant reservoir of infection.
All new bought-in or incoming sheep should be quarantined for 28 days to avoid the introduction of a different strain of foot rot or CODD. Sheep should be carefully examined while in quarantine for signs of foot problems with any developing lameness not to be added to the flock.
Attention to the foot health of the entire flock, and avoidance of transmission of highly infectious pathogens coupled with rapid action, regular foot baths, vaccination and good biosecurity will underpin successful management of lameness prevention.
Brief summary of some types of lameness in sheep
Foot rot and scald account for 90 per cent of lameness in most sheep farms.
Scald occurs between the hoof horns and is usually a reddish discolouration and moist with the loss of hair. Inflammation occurs in the skin between the digits. With scald there is generally no bad smell and little or no involvement of the hoof.
Foot rot is a very common disease (in 80 per cent of flocks) of the hoof that originates between digits but develops to an under-run hoof and it also has a distinctive smell. Foot rot is a highly infectious disease and is commonly caused by two bacteria, Dichelobacter nodosus and Fusobacterium necroporum.
Notably, D.nodosus thrives and spreads rapidly in the UK’s moist temperate climate. With easy transmission from sheep to sheep, proper control and prevention must focus on the whole flock as it is particularly transmissible when sheep are confined in a small area, eg, during housing, in handling yards, contaminated bedding or access routes.
Contagious ovine digital dermatitis (CODD) is regarded as one of the most severe foot conditions affecting sheep. Sheep suffering from cases of CODD can be left permanently lame due to changes to underlying tissues and bone within the hoof.
Other foot conditions include Shelly Hoof, White Line abscess, and Toe Granuloma.
A very useful vaccine is available to prevent and reduce the incidence of the foot rot disease. It is widely used and is a successful deterrent.
Hoof Care and Footbaths:
As with most conditions, “prevention is better than cure” and regular foot baths with a safe and effective compound is a sound financial investment. Footbaths have been used as routine prophylactics for lameness for many years and most have centred around copper, zinc, or formalin type ingredients.
Some new alternatives for hoof care are now available which on the basis of clinical field trials hold up very well when compared to copper or formalin. In addition, these newer compounds are safer to the handler and less toxic to the environment. Formalin, for instance, is known to be carcinogenic, toxic, and irritant, and copper is environmentally toxic and can be toxic to sheep.
A new alternative to these traditional types of footbaths is tea tree oil (TTO), an essential oil which has been shown to have many beneficial medicinal uses as an antiseptic, anti-inflammatory, antifungal, and antibacterial agent, where it is used routinely in skin and epidermal care. TTO has been proven to have potent antibacterial and anti-inflammatory actions and also promotes health in the hoof keratin.
Hoofsure Endurance from Provita is a proven and safe footbath solution, a proprietary blend of organic acids, tea tree oil, and wetting agents. It has been highly successful in the field, in both sheep and cattle, in preventing lameness and thereby avoiding the heavy financial costs arising from the subsequent appearance of lameness.
Comparative field trials were performed using Hoofsure Endurance against copper sulfate and formalin footbaths, albeit primarily on cattle lesions, but the data is very much transferrable to sheep because the infection cycle is very similar. Notable research shows that Hoofsure Endurance is up to 44 per cent more effective than formalin and copper sulfate with proven antibacterial activity.
Queen’s University Belfast performed a time kill study on Hoofsure Endurance to determine its inherent antibacterial nature compared to formalin and copper sulfate. See chart above.
Under clean test conditions, within five minutes copper sulfate and formaldehyde were 99.99 per cent and 99.9999 per cent less effective than Hoofsure Endurance. Under dirty conditions, within five minutes the efficacy of copper sulfate and formaldehyde were reduced even further while the efficacy of Hoofsure Endurance was unaffected by the presence of dirt.
The dirty conditions were designed to replicate a typical on-farm challenge for footbath preparations. Hoofsure Endurance exceeded the efficacy test requirements under all test conditions whilst copper sulfate and formaldehyde failed to meet the test criteria.
This laboratory data was backed by a recent independent study on the effectiveness of footbath solutions in sheep found that 65 per cent of sheep improved after one pass through a footbath containing Hoofsure Endurance at two per cent dilution rate.
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