Osteochondrosis and arthrosis in pigs. 3. A comparison of the incidence in young animals of the Norwegian Landrace and Yorkshire breeds

An investigation concerning the occurrence of osteochondrosis and arthrosis in 2 materials totalling 63 pigs of the Landrace breed and 63 of the Yorkshire breed is described. The animals were bred under the same conditions of feeding and housing. The differences should therefore mainly be of genetic origin. Both breeds were highly improved, Landrace the most. In general, Yorkshire pigs showed a lower incidence and a less marked degree of osteochondrosis and arthrosis than Landrace pigs. Statistically significant differences (P < 0.01) were demonstrated in the distal epiphyseal plate of the ulna, in the intervertebral joints of the lumbar region and in the medial condyle of the femur in 1 of the materials. The Landrace pigs had longer bodies, broader hindquarters, shorter femurs, and the stifle had a different shape as compared with Yorkshire pigs. There thus seemed to be a connection between exterior features, joint and bone shape and the occurrence of joint lesions. Differences among litters within breed were also demonstrated.

Osteochondrosis and arthrosis in pigs. VI. Relationship to feed level and calcium phosphorus and protein levels in the ration

Eight feeding experiments, each comprising 48 boars or gilts, were carried out. The factors feed level, Ca, P and protein levels were varied within practical physiological limits. The animals were slaughtered at close to 100 kg live weight. Lesions in joints and bones were of a noninfectious, non-rachitic nature and of the osteochondrosis and arthrosis type. Ten to 12 g Ca and approx. 10 g P/kg ration gave histomorphologically seemingly more optimum structure of the spongious bone tissue and a higher ash percentage in bones than 7 g Ca and 6 g P, or unbalanced mineral levels in the ration. However, there was no significant difference in degree or incidence of joint and bone lesions between mineral groups. Neither were there such differences present between feed level groups or protein level groups. This may for the feed level groups be partly due to the low feed level pigs having a longer period of time during which they were highly susceptible to the development of lesions. The low feed level animals had longer long bones at 100 kg live weight than the high feed level animals. The length of the vertebral column was, however, approximately similar in the 2 feed level groups. The angles of the condyles and head of the femur according to the length axis were influenced by feed level or growth rate, most probably by an effect on the endochondral ossification.

Osteochondrosis and arthrosis in pigs. IV. Effect of overloading on the distal epiphyseal plate of the ulna

The effect of overloading on the distal epiphyseal plate of the ulna is described. The right forelegs of 6 pigs were fixed such that the pigs were forced to walk on 3 legs during 2 periods, the first of 12 days duration at about 50 kg live weight, and the second of 7 days at about 100 kg live weight. Osteochondrosis developed to a more marked degree in the left than in the right epiphyseal plate of the ulna, but this did not lead to reduced lengthwise growth of the bones to any great extent. The overloading led to reversible changes in the distal epiphyseal plate of the ulna. It is conceivable that this was due to disturbances in the metaphyseal blood flow. It is also conceivable that the overloading was neither great enough nor of sufficient duration to affect the epiphyseal blood flow with consequential irreversible damage to, and premature closure of, the epiphyseal plate.

Osteochondrosis and arthrosis in pigs. II. Incidence in breeding animals

Joint and bone lesions in Norwegian breeding pigs are described on the background of an investigation involving 174 sows and 155 boars from 7 months to 4½ years old. Lesions, which consisted predominantly of arthrosis, degeneration of intervertebral discs, spondylosis and epiphyseal separations, were demonstrated frequently in both sexes. Osteochondrosis, a condition previously demonstrated frequently in slaughter pigs, had either completely healed, undergone repair or developed into an arthrosis by the time the animal reached an age of about 1½ years.

Whereas a higher incidence of arthrosis of the intervertebral joints was found in boars than in sows, the reverse was true as regards degeneration of the intervertebral discs and anchylosing spondylosis. Possible reasons for this are discussed. Norwegian pigs show a higher incidence of lesions in the lumbar region of the vertebral column than has been described up to the present time in other countries.

Osteochondrosis and arthrosis in pigs. V. A comparison of the incidence in three different lines of the Norwegian Landrace breed

Investigations were carried out on 289 slaughter pigs, 56 breeding boars, and 51 breeding sows in a selection experiment started in 1964. The animals belonged to 4th–6th generations. One line has been selected for thin backfat and rapid growth (LBL) and 1 for thick backfat and slow growth (HBL). In addition a control line (GL) not subjected to selection was established in 1967. The pigs were kept as far as possible under identical conditions of housing and feeding, so that differences between lines should be primarily of genetic nature. The skeleton, measured as the length of bones and vertebral column, was statistically significantly smaller (P < 0.01) in HBL than in CL and LBL. The difference between CL and LBL was slight. No essential proportional changes in the skeleton took place. Patho-anatomical findings in the skeleton comprised, in all 3 lines, osteochondrosis, arthrosis, degeneration of the intervertebral discs, spondylosis, and epiphyseal separation. There were a lower incidence and statistically significant (P < 0.01) lower degree of total lesions in joints and bones in HBL, both as regards the slaughter pigs, boars and sows. The fact that the lumbar region of the vertebral column consistently showed the greatest difference in degree and incidence of lesions between the lines, suggests that this becomes the weakest skeletal part in pigs with a rapidly growing skeleton.

Osteochondrosis and arthrosis in pigs. I. Incidence in animals up to 120 kg live weight

Joint and bone lesions in growing pigs are described on the basis of post-mortem examination of 341 gilts, boars or castrates from 10 to 120 kg live weight, and 869 separate bones from pigs between 80 and 115 kg live weight at slaughter. No evidence of rickets or generalized osteodystrophia fibrosa was found. Lesions occurred in both sexes. The typical osteochondral lesions were most often symmetrical, occurred at certain sites in joints and epiphyseal plates and were most obvious in the elbow and stifle joint, and in the distal epiphyseal plate of the ulna. Lesions of varying degree could be demonstrated in most pigs at 90–100 kg live weight. The use of the diagnosis osteochondrosis is suggested for local primary non-inflammatory disturbances which lead to a failure of endochondral ossification in joint cartilage as well as in epiphyseal plates. The diagnosis arthrosis is used when the superficial layer of the joint cartilage is affected. Investigations of the early changes in the medial condyle of the femur suggest that the osteochondral lesions start in the deep layers of the joint cartilage. Arthrosis occurred frequently in the lumbar intervertebral joints of Norwegian pigs. Otherwise the lesions appeared to be identical with those described from other countries.

Perthes' disease: an experimental and clinical study

Images