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This article was published in 1949
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK
BENT LEG IN LAMBS
GRAHAME EDGAR, B.V.Sc., Director of Veterinary Research. Glenfield
"Bent Leg" is a popular name employed to describe an unusual non-infectious condition involving the fore limbs of young lambs. On account of the deficiencies in the knowledge and etiology of the condition a more scientific name has not been given as yet to the condition. Most cases occur in lambs from three to four months of age, but younger animals may be affected and in one instance we encountered the condition in lambs several months of age. It is characterised by a bending out or straightening of the knee joint. It will be recalled that the fore limbs of lambs normally have a slightly knock-kneed confirmation, which in some flocks is developed to a more mnrked degree.
The condition has been encountered only in the Holbrook, Jerilderie, Bombala, Tamworth and Bathurst Districts.
A considerable amount of investigational work has failed so far to throw any light on the cause of the problem. A comprehensive series of experiments were undertaken on a property in the Jerilderie district. The experiments were based on the hypothesis that the condition was a type of Rickets, which had been suggested following histological examination of costo-chondral articulations and the epiphesial cartilages of long bones. A vitamin D supplement was administered to one group of lambs, but this failed to indicate nay improvement in the growth rate of the lambs as compared with on identical group which was not given the supplement. Bent Leg did not appear in either the treated or control groups of lambs.
The variable evidence of the condition has proved one of the most baffling features in our investigational work. The property on which these experiments were conducted has experienced cases of "Bent Leg" in successive lamb drops and the history of the incidence on this property suggested it as it favourable centre for investigational work. However, as stated above, following the inauguration of experimental work not a single case appeared amongst the lambs in either group. This course of events has been characteristic of "Bent Leg." It will occur on a property for one season and, without any significant change in management, does not appear in the lamb drops of successive seasons. In some instances it has happened only during one lambing and has not been encountered again.
The theory that the condition is a form of Rickets is difficult to reconcile on histological grounds and in the light of our experience in administering vitamin D to lambs a property in the Jerilderie district. The indications are that lambs in New South Wales receive an adequate intake of vitamin D from their environment to maintain normal rates of growth.
We have examined the possibility of the condition being linked with a manganese deficiency. On one of the effected properties in the Holbrook district analysis of the pastures for manganese showed a variation between 250 and 480 parts per million; which is relatively high.
We have been unable to collect any evidence that the condition is associated with a calcium-phosphorus metabolic disturbance.
It is possible that some trace element excess or deficiency are contributing factors in the etiology; and we are interested in having reports of cases appearing in flocks in any parts of the State.