Observations on swayback disease of lambs in South East Scotland
Barlow, R. M.
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The investigation,embodied in this thesis, comprises a re-appraisal of the swayback problem,as seen in East and. South-east Scotland. The observations ih the field, and laboratory, have shown the condition to be even more closely allied to enzootic ataxia, in Australia,than was formerly apparent.it has been shown, that the disease in the area studied) is in some cases associated with hypocuprosis of herbage, though this was not generally the case. Confirmatory evidence has been produced for the usefulness of copper supplementation as a prophylactic measure, and trials with an injectable form of copper i'have been carried out. It has been shown that on sway-back farms, a fall in the blood copper levels of ewes occurs during pregnancy, which may be alleviated, lor prevented by copper supplementation, Circumstantial evidence has been produced to indicate that the availability of natural herbage,during the last critical period of pregnancy may be a deciding factor in the development of the disease. In turn, this may depend upon the geography, and pasture management of the affected farm;in addition to climatic conditions.The clinical signs, and pathology of a representative number of cases from each outbreak, have been studied in some detail. The observations made, agree with, and extend, those of previous authors in many respects.This study has been allied to a consideration of the normal foetus, and newborn lamb, using identical techniques. It has been shown, that the cerebral lesion has little apparent, clinical, significance, and that the ataxia is not due to a true spastic paralysis, but may result from lesions in the proprioceptive pathways, on the tract controlling motor activity.Comparison with the foetus, indicates strongly: that the lesions may result from arrested development, or maturation of nervous tissue, and not from a primary demyelinating influence. The causal factor(s) in such a process, remain obscure, though deficiency of copper plays a major role. The evidence, at present available, would indicate that this may not be the only factor involved. It has been suggested that others may occur in spring herbage, and might possibly be normal organic constituents.