The composition and metabolism of bracken (Pteris Aquilina), with special reference to its influence on animal health
Raafat, Mohammed Ali
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The first cases of bracken poisoning were recorded in 1893 by Penberthy and Storrar. Since then, most investigators have come to the conclusion hat the fatal results produced by feeding cattle and horses on a diet composed of bracken, are due to he presence of a cumulative poison. No conclusive evidence of bracken poisoning in sheep has been recorded.During recent years there has been a heavy mortality of cattle grazing on bracken infested hill land in Scotland. It has been suggested that this might be due to the Hill Cattle Subsidy Scheme (196) requiring the cattle to be on the hill continuously for 16 weeks. Although bracken poisoning has caused much anxiety to farmers in Great Britain, it has also been a source of trouble in other parts of the world, e.g. Europe, the United States of America, and Australia.In spite of the work of several investigators under different experimental conditions, the aetiology remains obscure and as yet, no complete examination of bracken for toxic constituents has been made. Since Greshoff in 1908 mentioned the presence in young bracken shoots of a glucoside, which by enzyme hydrolyis produced hydrocyanic acid, little attention has been paid to this constituent. It was therefore considered essential that an examination should be made of the composition and metabolism of bracken including an examination of the significance of this cyanide fraction. In the last three or four years studies on the inactivation of thiamine by bracken ave been reported by different investigators in Great Britain and the United States of America, Since these experiments have been confined to rats and horses, the opportunity has been taken to extend this work and examine the significance of the antithiamine activity of bracken in the aetiology of bracken poisoning in ruminant animals.