F.C. 20.1 Apr, 1993

What is bloat?

Bloat is a digestive disorder characterized by an accumulation of gas in the first two compartments of a ruminant's stomach (the rumen and reticulum). Production of gas (primarily carbon dioxide and methane) is a normal result of fermentation processes. The gas is usually discharged by belching (erutication) but, if the animal is unable to remove the excess gas, pressure builds up in the rumen-reticulum exerting pressure on the diaphragm which prevents the animal from inhaling, and bloat occurs. The most common type of bloat is frothy bloat where gas builds up in a foam or froth above the rumen contents and the normal belching is inhibited.

Observable bloat can occur after as little as 15 minutes of grazing. Often the animal bloats only mildly and stops eating. The discomfort is eventually relieved. In more severe bloat, the animal's rumen is distended by ballooning of the rumen, it urinates and defecates frequently, bellows and staggers. Death, due to restricted breathing and heart failure follows unless action is taken.

When is it likely to occur?

Bloat can occur on any forage that is low in fiber and high in protein but is most common on immature legume pastures. Bloat has been observed on alfalfa, white clover, and red clover pastures but is rare on trefoil sainfoin and vetch pastures. It usually occurs when cattle or sheep are first turned onto legume pastures. It seldom occurs on grasses, (or pastures with at least 50% grass), coarser pastures, or hay. Bloat usually follows a heavy feeding or grazing period. Animals that are hungry or greedy feeders are most susceptible. Frost, dew or rain on the field often increase the likelihood of bloat. Bloat incidence is likely to be increased during periods of rapid plant growth in the spring or following a summer rain.

Thus, most bloat occurs:

How do I reduce the occurrence of bloat?

What do I do if bloat occurs?

When bloat is observed, immediately remove all animals from pasture and offer dry hay. This will reduce the bloat problem in all animals that will eat. Causing bloated animals to walk is also helpful. Bloat can cause death in as little as 1 hour so it is important to be prepared to render emergency treatment. Materials and directions for use can be obtained from the local veterinarian.


Dan Undersander
Dave Combs


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