Mitigating Fall Forage Challenges for Livestock Producers

By Andi Anderson

As the fall season ushers in cooler temperatures and the likelihood of frost increases, livestock producers must remain vigilant about a range of forage-related challenges that could impact their animals. Prussic acid poisoning, nitrate poisoning, and bloat are among the key concerns during this transitional period.

Understanding Fall Forage Challenges:

• Prussic Acid Poisoning: Prussic acid poisoning is a threat caused by the accumulation of prussic acid (hydrogen cyanide) in forage plant tissue. This toxic substance results from a chemical reaction between two naturally occurring plant molecules, cyanogenic glycosides and degrading enzymes.

Normally, these two compounds are separated by plant cell walls. However, a frost event can be a game-changer. When frost freezes the water in plant cells, it ruptures the cell walls, allowing prussic acid to form.

• Nitrate Poisoning: Nitrate poisoning is another concern associated with feeding forages after frost. Frost can hinder the growth of actively growing plants, preventing the conversion of nitrates into proteins. This disruption leads to the toxic accumulation of nitrates in the plant tissue.
• Bloat: Bloat can also become problematic when grazing frost-damaged forage legumes like alfalfa and clover.

Mitigation Strategies for Fall Forage Challenges:

To safeguard livestock from these forage challenges during the fall, consider the following strategies:

• Remove livestock from pasture on nights when frost is forecasted.
• After a killing frost, do not graze until the forage is dry, usually taking 5-7 days.
• Following a non-killing frost, wait at least two weeks before grazing.
• Avoid grazing forages with a high potential for prussic acid poisoning when they have new growth.
• Prevent selective grazing of forages with new growth by employing heavy stocking rates and rotational grazing.
• When feeding silage made from forages with a potential for prussic acid toxicity, allow six to eight weeks for proper ensiling.
• Be cautious of nitrate accumulation in forages after frost.
• Allow primarily legume pasture to dry for a few days after a killing frost to reduce the risk of bloat.
• Supplement with a fiber source like dry hay or grazing cornstalks post-harvest to reduce bloat.
• Ensure livestock are not overly hungry before turning them out on fresh pasture each morning by providing additional forage.
• Utilize a bloat protectant when necessary.

If you are uncertain whether a specific forage is safe to feed, it is always advisable to consult with a veterinarian or livestock nutritionist. By proactively implementing these strategies, livestock producers can protect their animals and ensure a smooth transition into the cooler months.

Photo Credit: istock-deyanarobova