Lame sheep are a costly presence in any flock due to the costs of treatment, the costs of control and most significantly due to the adverse effects of lameness on productivity, fertility and longevity. These costs will reduce the output per ewe, as well as the output per hectare in a flock.
In order to decide on the control measures to take it is important to first establish the prevalence of lameness in a flock. If more than 5% of the flock is lame then a control plan is needed. The most common causes of sheep lameness include scald and foot rot. These diseases are infectious and can be spread easily from sheep to sheep.
Control measures that a flock should undertake can be summarised in a Five Point Plan
Number 1 is Treatment – It is essential that all lame sheep are caught, the cause of the lameness is established and then treated appropriately. A good time to do this is after weaning. Treatment may include the use of injectable antibiotics or footbaths. Your veterinary practitioner is best placed to advise you on the treatments that are likely to yield the best results for the condition you are treating.
Number 2 is to Avoid spread – Diseases such as foot rot and Contagious Ovine Digital Dermatitis or CODD are infectious and will spread between sheep at high traffic areas such as gateways and feed troughs, as well as anytime that the sheep are gathered. Footbaths can be helpful to reduce the spread of disease when sheep have been gathered. It is important that the sheep’s feet are reasonably clean before foot bathing as the footbath will not be able to penetrate through to feet that are clogged with mud. Ensure that the footbath is mixed to the correct concentration, that you allow the appropriate amount of contact time recommended and that the sheep have a dry concrete area to stand on for about an hour or so after the footbath so that the feet will dry.
Number 3 is to Vaccinate – It is possible to vaccinate in order to prevent foot rot. The vaccine can be used to reduce the overall levels of foot rot in a flock. It contains 10 strains of Dichelobacter nodosus, the bacteria that causes foot rot. For correct advice on how to use the vaccine it is important to speak to your veterinary practitioner.
Number 4 is to Cull – It is recommended that persistent offenders, that is sheep that are recurrently lame and don`t respond to treatment, should be culled. For this it is important to keep accurate records so that the same ewes are not retreated on multiple occasions. These ewes are not paying their way and are a constant source of infection to others.
Finally number 5 is to Quarantine – All incoming sheep should be quarantined to avoid the introduction of a different and perhaps more virulent strain of foot rot or CODD. During quarantine their feet should be examined and they should be run through a footbath. Lame sheep should never, ever be added to the flock.
Foot rot is one of the most common infectious causes of lameness on Irish farms. It causes economic losses through reduced live weight gain in lambs, reduced fertility in ewes and reduced mobility. It is a debilitating and painful condition. It is highly infectious and spreads easily from sheep to sheep. Foot rot can be recognised by a foul, very distinctive smell and underrunning of the hoof causing the sole and the hoof wall to separate.
Footrot is caused by two separate bacteria. Fusobacterium necrophorum, the bacteria that causes scald, is found in the intestines of ruminants and is passed out in dung onto the field. This bacterium first infects the hoof space, particularly when it is damaged due to trauma or wet conditions. Foot rot occurs where scald is already established and the sheep come in contact with a second bacterium called Dichelobacter nodosus. This second bacterium is able to enter the hoof and cause significant damage. Foot rot is a sheep-to-sheep disease and control and prevention must focus on a whole flock health plan.
Control includes first trying to prevent foot rot from ever entering the flock. Foot rot can enter a flock on the feet of infected ‘bought in’ sheep. It is important therefore for farmers to have a biosecurity plan in place. All sheep should be isolated on arrival on farm and quarantined for 4 weeks. Sheep should be regularly checked for signs of lameness during this time and treated as advised by your veterinary practitioner.
Foot trimming was long recognised as an appropriate management technique for sheep until considerable research suggested that routine trimming can increase levels of lameness. Routine hoof-paring is therefore no longer advised. In fact it has been shown that trimming even the hooves of lame sheep may lengthen the time it takes for them to heal. Hoof-paring is therefore now only recommended for very particular cases of lameness such as shelly hoof.
Formalin or zinc sulphate footbaths are an important part of foot rot control. Solutions must be used at the concentrations recommended by the manufacturer. Stand sheep on a clean, dry surface for at least an hour afterwards. Then turn sheep out onto a clean field, that is a field that has not held sheep for at least the past two weeks.
It is important to treat cases of foot rot early – the sooner the better. Your vet will advise you on the most appropriate treatments for clinical cases. Early treatment with an injectable antibiotic is associated with a greater chance of success.
Chronic cases that don`t respond to 2 or 3 treatment attempts must be culled otherwise they will act as a constant source of re-infection for the rest of the flock.
There is a foot rot vaccine available and this should be incorporated into any foot rot control plan in a flock. The vaccine contains ten strains of Dichelobacter nodusus the organism that causes foot rot. Sheep do not produce a natural antibody response to this bacterium. This means they will never develop a natural immunity to foot rot and will remain susceptible year after year. This is why vaccination is so important. It has been shown that there is a cost-benefit to vaccination when levels of foot rot exceed 2% of the flock at any one time. Used correctly, this vaccine is an important part of successful foot rot control. For advice on the correct use of the foot rot vaccine speak to your veterinary practitioner.