Bloat in Pastures

 Knowledge Nuggets | Factsheets | Research Papers

Knowledge Nuggets

  • 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 relative to the fine bloatable 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.
  • Legumes with tannins will actively reduce bloat rates when consumed in conjunction with bloat causing legumes. Tannin contents vary with different legume species. Purple and white prairie clover are known to be quite high in tannins. Sainfoin is next in tannin levels. Birdsfoot trefoil is lower than these others and may vary in content the most. Grazing research at AAFC Lethbridge and Swift Current has shown a 95 - 98% bloat reduction when sainfoin is present at 25% of a mixture with alfalfa or greater.

Bloat Caused by Legumes - available in PDF format

Bloat Effects Can Be Reduced Through Management

Bloat in Cattle - AB

Bloat in Cattle - available in PDF format

Controlling Bloat in Cattle - available in PDF format

Foamy Pasture Bloat - available in PDF format

Prevention of Pasture Bloat In Cattle Grazing Alfalfa - available in PDF format

Research Papers

A candidate gene marker for bloat susceptibility in cattle? - available in PDF format

A review of the development of a bloat - reduced alfalfa cultivar - available in PDF format only

Bloat in cattle grazing alfalfa cultivars selected for a low initial rate of digestion: A review - available in PDF format only

Condensed tannin concentrations found in vegetative and mature legumes grown in western Canada - available in PDF format only

Effect of condensed tannin on in vitro ruminal fermentation of purple prairie clover (Dalea purpurea Vent)cool-season grass mixture - available in PDF format only

Effect of grazing mixtures of alfalfa and orchardgrass grown in strips on the incidence of bloat in cattle - available in PDF format

Frothy bloat in ruminants: cause, occurrence and mitigation

Practical measures for reducing risk of alfalfa bloat in cattle - available in PDF format

The effect of feeding hay before fresh alfalfa on the occurrence of frothy bloat in cattle - available in PDF format only
  For more information about the content of this document, contact Grant Lastiwka.
This document is maintained by Linda Hunt.
This information published to the web on January 9, 2004.
Last Reviewed/Revised on February 28, 2018.

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