Bloat

What is Bloat?

Ruminant animals produce large volumes of gas during the normal process of digestion. This gas either is belched up or passes through the gastrointestinal tract. If something interferes with gas escape from the rumen, bloat occurs. 

Bloat is a risk when animals are grazing young, lush pasture, particularly if the pasture has high legume content e.g. clover. 

High Risk Times for Bloat

• Swards with a high sward clover content >40%.
• Turning animals from grass only swards to graze grass clover swards. 
• Turning hungry animals to graze mixed grass clover swards.
• Tight post-grazing sward height of less than 4cm on previous grazing.
• Low DM% in grass - wet weather or heavy dew on the pasture. 
• Very lush grass - low pre-grazing herbage mass, after grass etc. 

Bloat Prevention 

• Make sure cows enter the paddock as a full herd - hold cows in the yard.
• Have bloat oil in the water in the collecting/holding yard.
• Have bloat oil in the water trough in the paddock. 
• Introduce 2 - 3 kg DM/Day of grass silage at milking. 
• Avoid under feeding cows (low post grazing sward height).
• Use of strip wires - 2-3 hour break. 
• If possible avoid switching from grass to high clover content paddocks. 
• Avoid switching from grass to grass clover swards as much as is possible.
• Keep post-grazing sward height to 4-4.5cm. 
• Avoid turning hungry animals onto grass clover swards. 
• Provide a small area in paddock for the first 2 - 3 hours after turnout to prevent initial gorging process. 
• Provide fibre, grass silage in the diet at milking. 
• Identify high risk paddocks and monitor cows closely when grazing these. 
• Check cows after initial turnout and regularly for first three hours during the high risk period. 

Bloat Prevention Summary

• Be Consistent - problems going from grass to grass clover swards. 
• Little and often - use a strip wire to control grass allocations. 
• Oil - use bloat oil during periods of high risk. 
• All cows out after milking together; makes sure the first cows milked don't gorge on clover before the others get out. 
• Target the fibre in the diet.