Evidence suggests that although sheep lameness incidence is not getting worse, it is also not getting better and this is partly due to the fact farmers have not been provided with a practical, manageable protocol.
Laura Green, professor of epidemiology at Warwick University, explains that national lameness prevalence has stayed at about 9-10% since 1994.
However, there is huge variation between farms, with the best producers achieving an incidence of 1-2% and the worst at 20% or more.
And with the cost of foot-rot from treatment and labour alone, standing at £8.38 a ewe, getting on top of the problem makes sense from both a welfare and financial perspective.
Prof Green says the main difference between the top and bottom performing flocks is the speed at which sheep are treated.
The cause of lameness
More than 90% of lameness is due to foot-rot (pictured right) and interdigital dermatitis (scald), both of which are caused by the bacteria Dichelobacter nodosus, Prof Green explains.
Contagious ovine digital dermatitis (CODD), is a less understood, but problem disease, with a flock tending to see 50% of sheep affected in the first year with the disease rumbling on from then onwards.
Dichelobacter nodosus is spread via the ground and thrives in warm, damp conditions, meaning most farmers see problems when stock are housed and closely stocked.
Ideally lame sheep should be housed separately to reduce the cycle of infection. Scald is a precursor to foot-rot, so by tackling scald early, the problem can be prevented from escalating.
The only time foot-bathing is a relevant treatment is in response to scald, however, it has a role to play in preventing disease, says Prof Green.
“Ideally stock should be run through a foot-bath every time they are gathered or housed. And a long acting antibiotic such as oxytetracycline is recommended for the treatment of foot-rot.”
One of the main benefits from effective control of foot-rot in ewes is a reduction in lamb scald because of less overall contamination at pasture.
Lameness has a highly complex epidemiology which means a combination of steps are needed to solve the problem, explains consultant vet for FAI Farms, Ruth Clements.
“We know scald is a precursor to foot-rot, but we can’t solve the issue with just one step. The bottom line is lameness is a huge problem on most farms, but up until now there has been no clear, practical protocol to tackling the problem.”
However, by working alongside sheep farmer, Ryan Haydon and drawing on research carried out by Prof Green, FAI Farms has created a new five-step management protocol designed to provide a long-term solution to lameness.
The approach is currently being trialled on three farms over a three-year period (see case study), with the hope to role out the protocol nationally:
1 Cull badly or repeatedly affected animals
- When a ewe has had more than one bout of foot-rot in a season she should be given a cull tag – this will help prevent the cycle of infection.
- When culling at this level is not practical, producers will have to accept it will take longer to get on top of the problem.
- Strategy will vary depending on lameness incidence and will need to be adjusted to fit individual farm circumstances.
- When farmers are breeding their own replacements, they can very quickly reduce lameness by culling lame sheep.
2 Quarantine incoming animals
- Make sure a good procedure is in place to separate bought in stock for four weeks after purchase.
- If practical to do so, run bought-in stock through a foot-bath and monitor lameness to ensure you are not bringing a problem into the flock.
- Buy from a source which is carrying out a strict lameness protocol.
- The idea is by all working to reduce lameness, lameness transmission is reduced down the supply chain.
3 Treat clinical cases early
- Treating lame sheep early brings strong financial and performance benefits with a greater proportion of lambs from early treated ewes staying alive and growing faster.
- Treating lame ewes with an antibiotic injection, and costing in time for doing so was shown to bring a net benefit of £6 a ewe in 2006. With increasing lamb prices, the cost benefit is only going to be higher today.
- Trial work found half of sheep that were lame once were lame more than once, meaning it’s crucial lameness is prevented from becoming a problem.
- It does take some effort to catch and treat stock, but it is well worth doing so – if needs be get in an extra pair of hands or a good dog.
4 Avoid the propagation of infection at gathering and handling
- Look at what is practical on farm as to whether foot-bathing is appropriate.
- Look at the handling area – if you gather on to a dirty holding area, is it possible to clean and improve drainage?
- Remember dirty concrete is just as bad as soil.
- Investing in a mobile handling unit may be worth while to prevent propagation of infection in one place.
- Gravel on entrance to the handling facility will help prevent poaching.
- Applying lime around water troughs, when poaching is a problem will reduce infection risk.
5 Vaccinate animals to stimulate immunity
- Foot-rot vaccination should be used in combination with a whole flock approach.
- The aim is to encourage immunity within the flock as an aid to improve the success of the other four steps.
- Treatment frequency will vary between farms, but could be biannual to start with going down to once a year as the challenge decreases.
- If a farm is continuously buying in stock, biannual vaccination may need to be maintained. For example, FAI Farms vaccinates in the winter before housing and then again in the summer after shearing.
- It’s important to vaccinate all breeding stock and rams.
Graham Dixon, Alwinton Farm, Rothbury
Following the five-step approach to lameness control has allowed Northumberland farmer Graham Dixon to cut lameness by 50% over two years in his flock of 1,200 ewes.
Alwinton Farm, Rothbury, is one of three commercial sheep farms trialling the protocol over a three-year period and his participation has resulted in a drop in foot-rot and scald from 10.25% to 5%.
Prior to implementing the new approach, Mr Dixon says 5% of lambs were not finishing in the target window before Christmas, because of lameness and subsequent growth checks.
Scald in lambs and ewes was at a high enough level to mean extra handling and added difficulties, and past protocol had meant spot treating and foot-bathing ewes about every three weeks./p>
All ewes and replacements are now vaccinated for foot-rot in the autumn, a step that has helped reduce lameness to the extent that they have almost stopped foot-bathing.
“We have seen much less scald in lambs and now there is no need to foot-bath lambs and we just spot treat. Prompt treatment of ewes and lambs is crucial to stop scald from developing into foot-rot,” says Mr Dixon.
The handling system has also been moved inside on to a concrete, easy to clean standing and hydrated lime applied where necessary.
Bought-in stock tups are quarantined, vaccinated, generally foot-bathed and monitored for lameness. “Ultimately when a ram is lame, he won’t do the job so it’s crucial they are sound,” he adds.
Mr Dixon has seen a big improvement in ram mobility since managing them in this way. “Vaccination has been a major success, but it cannot be done in isolation – it must be part of an overall programme.”/p>
Although the farm had always culled persistently infected ewes at about 3% a year, by implementing all the other steps the number of culls is becoming less and less as the trial progresses.
For foot-rot control, vaccination as part of an overall flock lameness reduction programme provides effective treatment for infected sheep, as well as long-term protection against the onset of the disease.
The Footvax vaccine allows sheep to build immunity to Dichelobacter nodosus – the key bacterium implicated in foot-rot. Unfortunately, unvaccinated sheep do not develop lasting immunity to this bacterium, which means they will always remain susceptible to the disease.<
Footvax vaccination programmes should be tailored to meet individual flock disease control requirements. Wherever possible, whole flock vaccination should be adopted.