Bloat in Pastures

Knowledge Nuggets

• The bloat-causing potential is related to the rate of digestion by rumen microbes. The fine portions of bloat-causing forages are digested rapidly whereas bloat-safe forages are digested slower.

• The greatest factor causing legume bloat relates to the percentage of fines relative to coarse material in the rumen at any point in time. Grazing management that forces the animals to consume the entire plant within a short time encourages the mixing of fines with coarse plant material. This can be done by grazing at a high stock density and frequent moves.

• The stage of growth or crop maturity is a very important factor in preventing pasture bloat because animals eat more coarse material as the crop matures.

• Alfalfa is known to be bloat-safe after a killing frost. However, as long as the alfalfa is alive, there is a risk of bloat.

• Alfalfa must first be killed and time is required to dry down the leaves before it is reasonably bloat safe.

• Animal susceptibility to bloat is related to the clearance of small feed particles from the rumen. Cattle that frequently bloat have a slower clearance of these small feed particles than non bloaters. This has been demonstrated in both feedlots and pastures.

• Uniform and regular intake is one key to managing animals on legume pastures.

• Bloat is less likely to occur if animals are turned out to pasture in the afternoon than in the morning because plant cells are less turgid in the afternoon resulting in slower rupturing of the cells during digestion.

• Swathing and wilting pastures is another strategy for reducing bloat. Wilting a swath for 24 to 48 hours can significantly reduce the incidence of bloat from 81 per cent to 50 per cent.

• Antibloat products are coming on the market to reduce the incidence of bloat. Experiments have shown that antibloat products reduce the viscosity of the foam in the rumen and can be effective in preventing bloat.