Foamy bloat of cattle. A review.

Bloat is a disorder of ruminants caused by retention of gas in the stomach. Gas is produced continuously and in large amounts in the ruminant stomach and is eliminated normaUy by the animal without difficulty. Sometimes, however, the rate of elimination falls behind the rate of production so that gas starts to accumulate in the rumino-reticulum (hereinafter called the rumen). If the disparity continues, it can lead to gross distention of the rumen -the intraruminal pressure may rise to as much as 70 mm Hg (41, 89) -and the animal becomes bloated. The inflated stomach mechanically interferes with respiration, which probably is further embarrassed by the absorption of CO2 from the rumen, and can cause death within an hour of commencing to feed (81, 105, 112, 315, 388). The imbalance of gas production and removal that leads to bloat results most commonly from excessive foaming of the contents of the rumen; this is the primary cause of bloat in animals feeding on legumes or lush young grass, and of feedlot bloat. Non-foamy or freegas bloat is less common than foamy bloat and results from a variety of causes. This review is concerned with foamy bloat, and especially legume (pasture) bloat. Feedlot bloat, which characteristically oeettrs in beef cattle fed on rations high in concentrates and low in roughages, and which may be chronic, will be discussed separately and in less detail. Extensive reviews of bloat appeared regularly between 1945 and 1960 (81, 82, 83, 190, 191) the last being that of Cole and Boda (81) in 1960. Since then the subject has been considered in varying degrees of detail by a number of authors (66, 78, 175, 183, 196, 322, 327, 379). The present review, which mainly covers the literature since 1959, should be read in association with that of Cole and Boda (81).