Studies on the alimentary tract of merino sheep in South Africa. XIII. The role of prussic acid in the aetiology of acute bloat

Abstract

It is shown that more than four times the amount of KCN is required to cause ruminal paralysis in sheep during active fermentation of lucerne in the forestomach than after a fast of 14 hours. This increased tolerance to KCN after feeding is explained on the basis of an accelerated elimination of HCN from the lungs resulting from the greater respiratory exchange, which in turn is caused by the absorption of carbon dioxide from the alimentary tract during fermentation. Similar results are reported by the artificial introduction of carbon dioxide into the rumen. Sheep showing paralysis of the rumen, caused by KCN, are able to eructate two litres of gas per minute introduced through the ruminal fistula. These observations, therefore, afford no evidence for incriminating the cyanogenetic factors in plants as being associated with the aetiology of acute bloat in ruminants.