Ensiling Sorghum-Sudan Grass: Key Management Guidelines
Sorghum-sudan grass is gaining interest among producers for its ability to regrow under warm, moist conditions, making it suitable for multi-cut hay systems or rotational grazing. However, challenges such as Manitoba’s cool, wet springs and weed competition often limit success.
Key Risks: Prussic Acid and Nitrates
- Prussic Acid Formation:
- Sorghum species contain compounds that release cyanide under stress conditions—similar to those that cause nitrate accumulation.
- High-risk situations include:
- Frost damage
- New regrowth after cutting or grazing
- High soil nitrogen with low potassium and phosphorus
- Young leaves and shoots can contain 2–25 times more prussic acid than stems (opposite of nitrate distribution).
Grazing and Harvest Guidelines
- Regrazing: Wait until new growth reaches 24–30 inches before grazing.
- After Frost: Delay grazing for 5–6 days to allow prussic acid levels to drop (up to 75% reduction).
- Hay: Curing reduces prussic acid; ensure proper drying before feeding.
- Silage: Ensiling significantly lowers prussic acid—wait 1–2 months before feeding to allow gas-off during fermentation.
Best Practices
- Monitor soil fertility and avoid excessive nitrogen without balancing potassium and phosphorus.
- Test forage for nitrates and prussic acid before feeding.
- Introduce sorghum-sudan gradually into rations and avoid feeding stressed or frost-damaged forage immediately.
