Lameness is a huge problem in the UK sheep industry.
It is estimated that each case of lameness costs a farmer £90 once the cost of medicines, time and loss of production (growth rates, fertility, twin lamb disease and milk production). With the average lameness incidence at 10%, lameness will cost £900 per 100 animals.
Footrot is caused by the bacteria Dichelobacter nodosus. There are 10 different strains, each producing chemicals of varying virulence that breakdown the hoof causing underrun horn of the sole and hoof wall, and produce a characteristic smell. Infected sheep carry the bacteria and can transmit it to other sheep even with no or minimal lameness. The bacteria spreads particularly well in long lush pastures, in heavy dew and rainfall, is found in high quantities around feed/water troughs and gateways, and can survive 10 days on pasture. So liming of high traffic areas is recommended to decrease spread, as well as liberal bedding when housed.
The advice is to NOT trim these feet – the underrun horn offers some protection to the delicate tissue underneath, and over-trimming can lead to granulomas. These animals should receive antibiotic injection and spray, and an anti-inflammatory pain relief injection.
If individual animals are treated within 3 days of the first signs of lameness (even a 1/6 lameness) then it may be possible to control footrot in a flock. If this is not possible then treatment of individual animals is unlikely to fully control the problem due to infected sheep spreading the bacteria on the pasture for other sheep to become infected. In these cases, foot-bathing should be considered (see later).
Scald is also caused by Dichelobacter nodosus and is the earlier stage of footrot. Both scald and footrot can become secondarily infected with another bacteria Fusobacterium necrophorum.
Scald manifests as inflammation of the skin between the toes, hair loss and moist oozy skin. If you run your finger between the toes, it will have the same characteristic smell as footrot. Foot bathing is also suitable if large numbers are affected, otherwise individual treatment with antibiotic sprays is recommended as soon as possible after a lameness is noticed.
Contagious Ovine Digital Dermatitis only causes 5% of lameness in sheep. The damage starts at the coronary band, where the horn meets to skin, and progresses down the inner hoof wall. There is no characteristic smell but cases may have footrot as well which will smell. As the name suggests, CODD is very contagious and 40% of the flock can become infected in a short space of time.
Formalin or zinc sulphate footbaths are NOT effective and are painful. An antibiotic footbath is required for CODD.
Foot bathing is a very useful tool in helping to control infectious causes of lameness but if not done properly it can spread the diseases more. It should be carried out on a dry day and the sheep should go through a bath of just water first to clean the feet. Sufficient concentrations of treatment and contact times are important and will vary depending what products are used.
If the handling system is not suitable or the sheep are not used to going through it then they are likely to just skip through and these contact times won’t have been achieved.
The sheep must then stand on a dry, clean surface for at least 20 minutes after bathing and then turned out onto pasture that has not been grazed for 2 week to avoid reinfection.
The advice is to NOT foot trim lame sheep as it delays healing and risks cross infection. Even routine foot trimming is not recommended, although if feet are overgrown then it should be performed with caution as over trimming can allow bacteria to penetrate more easily.
This vaccination is just one tool in the box to reduce footrot in a flock. The injection is given under the skin behind the ears and 2 injections 6 weeks apart are required initially. It is recommended that a whole flock is vaccinated to reduce disease risk from the environment. Depending on the prevalence of disease and the conditions, a further dose may be required at 4-5 month intervals, otherwise revaccination can be delayed until the incidence of disease challenge increases or climatic conditions worsen. Don’t forget the bought in stock.
In the UK, adverse condition tend to occur between March and May then again between October and December so vaccination should normally be completed 4 weeks before these periods if problems are anticipated.
AHDB have come up with a five point plan to assist in decreasing sheep lameness to the target of 2%. The combination of all 5 points gives the greatest chance of success. You may get away with just following 2 or 3 points until the flock is under any sort of stress eg. lambing, bad weather, at which point there is no ‘buffer’.
1. Cull out the worst offenders to build resilience – cull any animals that have had 2 incidence of lameness.
2. Quarantine incoming sheep for 4 weeks to decrease disease challenge. Bought in stock should be run through a footbath if available, and monitored. Ideally buy from a source that has a strict lameness policy.
3. Rapid treatment of clinical cases to decrease disease challenge. Ideally isolate clinical cases but this often isn’t possible.
4. Avoid spreading disease by liming around feed/water troughs and gateways, using a mobile handling unit and having a clean well drained handling area.
5. Vaccinate the whole flock with Footvax twice a year to establish immunity.