Also known as Osteochondrosis
Osteochondrosis is a generalized skeletal disease which leads to leg weakness. Leg weakness affects growers / finishers, sows and boars. The effects are rising or difficulty walking, swaying, misshapen limbs.
- Causes of Osteochondrosis >
- Effects of Osteochondrosis >
- Diagnosis of Osteochondrosis >
- Treatment & Control of Osteochondrosis >
Causes of Osteochondrosis
The changes have been demonstrated in piglets 1 day of age and may be congenital. Osteochondrosis becomes more obvious with age, although developing and healing lesions may occur at any one time.
Areas remain in developing bone or cartilage from the cartilaginous physis or epiphyseal growth plate separating (and metaphyseal end (shaft) and bone at the epiphyseal-articular surface. These cartilaginous areas and lead to structural weakness or distortion of the bone fracture, separation of the from the underlying cartilage and bone to cleft in the epiphyseal plate.
The cause appears to be a defect in the chondrocytes (cartilage cells) which do not mature normally. The matrix around them may prevent blood vessel formation and the formation of normal bone. Such lesions may eventually form bone. Growth rate and Heredity appear to affect their development, but diet or flooring type appear to have no effect. These changes lead to abnormal growth and change in the shape of bones and joints, including the vertebrae.
Erosion of the articular cartilage and develop painful osteoarthritis of the joint. Epiphyseolysis can result when the head of the femur is shed in rapidly growing animals.
Effects of Osteochondrosis
Present in up to 80% of pigs, particularly heavy, rapidly growing Meaty breeds such as race or Dutchland Swedish Landrace, Duroc or kept on hard flooring.
Clinical signs include shortening of the step, and buck knock knees and swaying of the forelimbs. In the hind limb the feet may be positioned too far forward, and pigs stand with their legs apart and show weakness at the pastern and swaying of the hind quarters. Changes increase with age.
Epiphyseolysis may lead to sudden hind limb lame ness and pain at the hip but not necessarily at the stifle or Hock. The affected leg is shorter than the unaffected one, but the thickness of the muscle mass makes identification difficult. Animals may be unable to rise, adopt a dog-sitting position and resent movement.
Epiphyseolysis occurs commonly in young screams when first delivered at or service. Osteochondrosis is a common cause of leg weakness and lame ness in young breeding stock and may progress to arthrosis (degeneration of the joints) and deformation of affected bones or resolve completely by 6.9 months of age. Forelimb weakness is obvious in some Duroc boars. Kyphosis (curvature of the spine) may also develop as animals attempt to spare affected limbs.
Diagnosis of Osteochondrosis
Clinical signs or bowed legs and swaying gait suggest the presence of osteochondrosis. Epiphyseolysis should be suspected where screams are delivered or where they become suddenly lame lame at or around service. Osteochondrosis can be confirmed by radiography from 63 days of age.
Confirmation at slaughter or post-mortem is more common. Deformation of the joint surfaces may be seen with collapse of the underlying bone.
Thickening of the cartilage with separation from underlying bone is the most prominent feature of the pathology and in joints, cartilage or flakes may become "joint mice" and produce synovitis (inflammation of the joints).
Deformation may be found at points in long bones affected and they may even fracture especially at the neck of the femur. Epiphyseolysis can be detected post-mortem by disarticulating the hip. The femur ends in a Severed neck and is sometimes surrounded by blood clot or muscle or bruised. The joint cavity remains filled with the head of the femur.
Osteochondrosis must be separated from inflammatory joint conditions such as erysipelas and mycoplasmal arthritis. Joint ill is usually confined to smaller pigs. Epiphyseolysis may be confused with pathological fracture of the femur fracture especially in hypocalcaemic gilt.
Treatment & Control of Osteochondrosis
There is no treatment although lame ness may resolve after moving to softer non-slip floors or deep bedding. The production effects that result from lame boars and screams can be overcome by use of Artificial Insemination.
Where epiphyseolysis is present, animals should be killed immediately without moving them. The condition can not be prevented completely, but its severity can be reduced. It has been suggested that the calcium and phosphorus levels and high nutrient density diets should be increased in order to supply adequate levels of these minerals in rapidly-growing pig.
The growth rate of breeding stock can be reduced. Exercise may be beneficial and gilt intended for breeding may be kept in straw yards. There is evidence that the condition may be under genetic control. It is much less common in Large White than in Landrace pigs with Duroc boars and genetic studies suggest that it can be selected against. This selection may simply reduce the stress on joints provided by large hams or other features or conformation.
In all cases where leg weakness or osteochondrosis are a problem, the condition of the floors should be improved, non-slip surfaces used and the possibility of fighting or other violent exercise minimized.
