Buying healthy sheep at saleyards
Farmnote 41/1995 [Reviewed July 2005]
By Preston Suijdendorp, Veterinary Officer (Chemicals), and Dianne Evans, Veterinary Extension Coordinator, South Perth
Summary
Minimise the risk of introducing disease on to your property by inspecting sheep carefully before buying, and by taking the listed precautions after the sheep arrive at your property. Methods are given for examining sheep for footrot, foot abscess, lice, scabby mouth, fleece rot, lumpy wool, pink eye, cancer and cheesy gland.
There is always a risk that sheep bought at a saleyard will introduce unwanted disease to your property. Buyers have little opportunity to find out the disease history of sheep before purchase. However, by carefully observing the sheep and taking some simple precautions, you can minimise the chances of disease being introduced.
Inspecting sheep in a pen
As you approach the pen, look for sheep holding feet in the air or limping. This can be a sign of virulent footrot, foot abscess or benign footrot. As you get closer to the pen, the sheep tend to forget about sore feet in their eagerness to get away.
At the pen side, observe sheep for the following:
- Head - scabs around the corner of the mouth, lips and muzzle may be scabby mouth. Watery, red or cloudy eyes may be pink eye.
- Back - areas of open and matted fleece may be fleece rot or lumpy wool.
- Sides - matted fleece may be lumpy wool. Rubbed or pulled fleece may indicate lice. Small, dirty matted areas in front of the shoulder or on the flanks may be cheesy gland.
- Rear - scouring may be due to worms. Scabby or ulcerated areas on the vulva of ewes may indicate cancer.
- Feet and legs - hair worn off the knees may indicate a sheep with sore front feet, which may be due to virulent footrot. Scabs on the skin of the feet above the coronet may indicate scabby mouth. Pus or blood at the coronet may be foot abscess.
- Distorted or overgrown feet are usually caused by running on soft ground. Lameness may result from breakoffs exposing sensitive tissues or abnormal strain placed on tendons and ligaments.
Closer examination
Checking for some diseases will require handling the sheep.
To check for lumpy wool, run a hand along the withers, back and flank of the sheep and feel for lumps in the wool. Parting the wool along the back may show fleece rot.
Tip over a few of the scruffiest sheep and part the wool down the flanks to detect lice, small brown insects about 1 to 2 mm long that move quickly away from the light.
Tip over sheep to check for virulent footrot. Reddened moist skin with hair loss between the digits or under-running of the horn of the hoof are early signs. If an Agriculture Western Australia Inspector is at the saleyards, consult her or him about suspicious cases. Footrot is most likely to be found in saleyard sheep in late spring.
On your property
When purchased sheep arrive at your property, take some precautions to minimise the chances of introducing disease:
- Drench sheep with ivermectin or moxidectin to prevent the introduction of drench-resistant worms onto the property.
- Treat introduced sheep for lice and isolate for the period recommended on the product used. If using a long wool treatment, treat again at the next shearing.
- Vaccinate sheep to the same standard as your existing flock as there is no guarantee that saleyard sheep have had any vaccinations.
- Keep introduced sheep separate from others for one to two months for observation. This has several advantages. Grass seeds will fall off, confining weeds to the 'introduction' paddock, and other diseases and conditions may show up.
Before mixing the introduced sheep with the existing flock, examine them again as previously described.
Diseases
Virulent footrot
Virulent footrot is difficult to detect in penned sheep, so any lameness or evidence of tender feet should be viewed with suspicion. Reddened, moist skin with hair loss between the digits or under-running of the horn of the hoof can be signs of footrot.
Properties infected with virulent footrot in sheep and goats are quarantined.
Footrot vendor declaration scheme
The footrot vendor declaration scheme is a voluntary, industry-based scheme co-ordinated through livestock selling agents who can provide declaration forms to vendors. Agents cannot make the declaration on behalf of clients.
The most important aspects of the scheme are that the owner believes that virulent footrot is not present on his/her property, and that the sale sheep have been inspected for signs of footrot.
The footrot vendor declaration does not guarantee freedom of disease.
Buyers should isolate the purchased sheep and look for signs of footrot. If virulent footrot is found within 14 days of the stock leaving the property, the vendor is required to remove the stock from the purchaser's property within seven days, pay all transport costs and accept that the sale is null and void.
Foot abscess
Foot abscess is another cause of lameness that may be confused with footrot. Foot abscess usually affects only one claw of one foot and is an infection of the deeper structure of the foot. There is usually considerable swelling and heat at the coronet at the top of the hoof, and there may also be a lot of pus. The hair loss and reddening of the interdigital skin seen with footrot is not seen with foot abscess.
Foot abscess mainly occurs during winter and spring, and mainly affects adult sheep. Even though it is caused by a bacterial infection, it is not contagious. Foot damage from rocky ground may increase the risk of foot abscess.
Lice infestation
Signs of lice infestation are rubbed or pulled wool on the flanks, but this is usually only seen in medium or heavy infestations in long wool. Lice infestation of sheep will reduce wool value.
Scabby mouth
Scabby mouth is a viral disease of sheep, goats and occasionally cattle. These scabs usually start at the corner of the mouth and move to the lips and muzzle. Scabs may also occur at the coronets above the hooves and on the ears.
The disease mainly affects young sheep and can cause a severe setback as a result of restricted grazing. Scabs remain infectious for long periods, and each new lot of lambs can be infected. Mixing infected bought-in sheep may lead to the rapid spread of the disease, especially if the property's sheep have not been previously exposed to it.
The disease can also affect people handling infected sheep, causing itchy sores.
Fleece rot
Prolonged wetting of long fleeces may lead to fleece rot. Tissue fluid from the wet skin causes matting of the wool fibres, and depending on the bacteria involved, coloured pigments may be produced. The value of affected fleeces is reduced.
Fleece rot is most common over the withers and along the back. Look for a more open tip to the fleece over the affected area, and saturated wool. Parting the wool will show matting and possibly discolouration of the fleece. Affected sheep are susceptible to recurrence of the disease and should be avoided, especially in wetter areas of the State.
Lumpy wool
Lumpy wool, also called dermatophilosis or dermo, is a bacterial infection of the skin which causes hard lumps of scab in the wool staple. This reduces fleece value and can make shearing difficult. Susceptibility to blowfly strike is greatly increased in affected sheep.
The lumps in the wool are easily found by running your hand along the withers, back and flanks. The infection can spread rapidly in suitable conditions such as when sheep are wet and kept in close contact with infected sheep. Jetting, dipping, yarding and transport of sheep on wet days can lead to infection.
Scouring sheep and worms
Scouring sheep could have one of a number of conditions, including nutritional scours caused by lush feed in winter and spring. Scouring at other times of the year is more likely to be due to disease, most commonly, worm infestation.
Resistance of worms to worm drenches is an increasing problem. Farmers buying saleyard sheep without a resistance testing history should drench introduced sheep with ivermectin (Ivomec®) or moxidectin (Cydectin®). After drenching, release the introduced sheep onto the wormiest paddocks on the farm, to dilute any resistant worms with the 'on farm' worms.
Pink eye
Pink eye is a bacterial infection of the eye which can result in reduced weight gain that normally lasts for about one week.
The first signs are watery eyes and blinking, then reddening of the eyes and cloudiness of the cornea. Signs usually disappear in one to two weeks although cloudiness can persist for several weeks. Occasionally an eyeball may rupture, causing permanent blindness.
The disease is spread mainly in summer by flies, dust and direct contact.
Cancer
Merino ewes that have had the radical mules operation are susceptible to vulval cancer as they get older. This is caused by exposure to sunlight and is not curable.
Signs of the disease are scabs or eroded areas on the vulva. Purchase ewes with tails docked level with the tip of the vulva, with some wool left on the top of the tail.
Cheesy gland
Cheesy gland is an extremely common disease of sheep. It causes abscesses of the lymph nodes and is a major reason for condemnation of carcasses. Most sheep show no obvious signs, although there may be discharging abscesses on the skin. It can be prevented by vaccination.
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