Ruminal tympany

Ruminal tympany, also known as bloat, is a disease of ruminant animals, characterized by an excessive volume of gas in the rumen. Ruminal tympany may be primary, known as frothy bloat, or secondary, known as free-gas bloat.

In the rumen, food eaten by the ruminant is fermented by microbes. This fermentation process continually produces gas, the majority of which is expelled from the rumen by eructation (burping). Ruminal tympany occurs when this gas becomes trapped in the rumen.

In frothy bloat (primary ruminal tympany), the gas produced by fermentation is trapped within the fermenting material in the rumen, causing a build up of foam which cannot be released by burping. In cattle, the disease may be triggered after an animal eats a large amount of easily fermenting plants, such the legumes alfalfa, red clover, or white clover. Some legumes, such as sainfoin, birdsfoot trefoil and cicer milkvetch are not associated with cause bloat in cattle. In feedlot cattle, a diet containing a high proportion of cereal grain can lead to primary ruminal tympany. The main signs in cattle are distension of the left side of the abdomen, dyspnea (difficulty breathing) and severe distress. If gas continues to accumulate, the right side of the abdomen may also become distended, with death occurring in cattle within 3–4 hours after symptoms begin.

In free-gas bloat (secondary ruminal tympany), gas builds up in the rumen and cannot escape, due to blockage of the esophagus.

Thomas Hardy's novel Far from the Madding Crowd depicts a flock of sheep suffering from bloat, who are treated by Gabriel Oak with a trocar to release the gas.

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