Grazing Legumes and Bloat - Frequently Asked Questions

What type of bloat do legumes cause?
The bloat legumes cause is usually a frothy bloat. Understanding frothy bloat and how it is caused may help understand bloat control on legume pastures.

What causes frothy bloat?
Frothy bloat results from the quick degradation and fermentation of plant material and rapid release of plant cell material. This material traps fermentation gases in a thick foam. The foam prevents the animal from being able to burp up the gases. The accumulation of trapped gases in the rumen may lead to the animal’s death.

At what stage are legumes at the highest risk?
Forage maturity is the most significant contributing factor in pasture bloat. The highest risk of bloat occurs when legumes are in the pre-bud or vegetative stage. As the plants mature the risk of bloat declines. Again this is because the fiber content in the plant increases as the plant matures and therefore breaks down more slowly in the rumen.

How do I reduce the risk of bloat when grazing legumes?

• Never move hungry ruminants into legume pastures in the morning. Cattle graze the heaviest in the morning.
• Put animals out to pasture when the plants are dry - water tends to speed up the rate of digestion.
• Feed another source of dry roughage, (long fiber), before grazing a bloat-causing legume pasture.
• Maintain a uniform and regular intake of legume forages. Once cattle have started grazing, leave them on the pasture, even at night.
• Graze full bloom mature plants.

Agdex 420/62-1, Feeding Legumes to Cattle

Prepared by Russel Horvey, Ag-Info Centre, Alberta Agriculture and Rural Development