Prevention of Pasture Bloat in Cattle Grazing Alfalfa
Alfalfa (or some clovers) are one of the most nutritious and productive forages available for beef and dairy cattle. While it is widely used as hay and silage, its use for grazing is limited due to the risk of pasture bloat. Despite this challenge, alfalfa grazing can significantly increase animal productivity and farm profitability when managed correctly.
High performance from alfalfa grazing requires an understanding of:
- The plant (growth stage, digestibility)
- The animal (behavior, adaptation)
- The environment (weather, grazing interruptions)
Alfalfa and Bloat Risk
Why Alfalfa Causes Bloat
- Alfalfa is digested 5–10× faster than most grasses.
- Rapid digestion leads to gas production and stable foam within the rumen.
- This foam prevents normal eructation (belching), causing rumen distension.
High-Risk Conditions
- Vegetative to early bloom stages (highest soluble protein content)
- Early in the day when soluble protein is elevated
- Immediately after rain, storms, or frost
- During rapid regrowth
- When animals are hungry at turnout
Lower-Risk Conditions
- Full bloom/post-bloom stages (lower soluble protein; thicker cell walls)
- After wilting or drying (soluble proteins reduced)
- Not immediately after frost—frozen alfalfa initially increases bloat risk
Animal Factors and Grazing Behavior
Cattle Must Learn to Graze Alfalfa
- New animals often avoid alfalfa initially, consuming grasses first.
- Bloat often appears 2–3 days after introduction, when alternate forages are depleted.
Uniform Intake Is Critical
- Prevent selective grazing of top-growth.
- Maintain consistent daily intake to avoid nutritional swings.
- Avoid removing and reintroducing cattle unless grazing was too early (bud stage).
Environmental Influences
Risk increases when grazing patterns are disrupted by:
- Heat
- Storms
- Biting flies
- Sudden shifts in forage availability
Producers should monitor closely during these periods to prevent “bloat storms.”
Grazing Patterns and Risk Timing
Cattle generally graze 3–4 times per day, with major bouts:
- Shortly after sunrise
- Early evening
Bloat most often occurs 1–1.5 hours after major grazing bouts, allowing producers to monitor during highest risk windows.
Common Sense Management Practices
- Avoid moving cattle in the morning. Move between 2–5 p.m. instead.
- The most dangerous period is ~2 days after a rain during hot, rapid growth.
- Maintain escape pastures for emergency removal.
- Begin grazing after 15–20% bloom to reduce risk.
- Avoid grazing paddocks “to the ground”—nutritional swings increase bloat risk.
- Observe whether animals are mixing grass with alfalfa.
- Haying ahead can help manage overly lush stands.
- After a killing frost, wait 2 weeks before grazing.
- Continuous grazing increases danger as regrowth increases bloat potential.
- Bloat-preventative products:
- CRC (Rumensin) bolus
- Alfasure liquid bloat preventer (highly effective if water source is controlled)
- Alfasure/Dioctol may also relieve bloat symptoms
Producer Summary
- Alfalfa grazing can significantly increase productivity but carries inherent bloat risk.
- No technology can guarantee “bloat-free” grazing—management is essential.
- Understanding how plant maturity, cattle grazing behavior, and environmental factors interact is key to minimizing loss.
- Successful producers balance the high profitability of alfalfa grazing with an acceptable level of risk, backed by sound management practices and monitoring.