Navigating fall grazing - understanding forage risks and safety

By Scout Nelson

Cover crops are making headlines in agronomy discussions. From soil health benefits to extended grazing periods, their use is varied. Yet, it's essential to treat these crops with care, especially as they become forage for livestock and as seasons change.

As summer fades and fall approaches, frost becomes a significant concern in the plains and Midwest, affecting safe crops for livestock consumption. Seed tags are crucial for livestock grazing, and new mixes like 13-way require more knowledge of each component. Frost introduces changes, triggering prussic acid formation and nitrate poisoning.

Prussic Acid Formation

Crops like sorghum and sudangrass after a frost have altered cell membranes. This change results in prussic acid formation, a cyanide form which, when consumed in large amounts, can be lethal, especially to ruminants. To minimize risks, avoid grazing areas for five to seven days post-frost.

If new shoots appear post-frost, wait until they grow 15-18 inches tall or after a complete frost kill. Hay and silage cuts aren't as concerning because drying and fermentation processes lower prussic acid levels.

Nitrate Poisoning

Grasses, especially oats and sudangrass, are susceptible to nitrate poisoning after frost. Nitrates accumulate, making haying or green chopping risky. It's best to wait five days post-frost and maintain a 6 to 8-inch cutting height to decrease the risk.

Ensiling helps lower nitrate levels, but if grazing, monitor the livestock's grazing patterns to limit nitrate consumption. If unsure, sending samples for lab analysis can guide feed strategies.

Avoiding Bloat

Post-frost, bloat becomes a concern, especially with high-quality forages like clover. Bloat occurs due to increased gas buildup in the rumen from protein and mineral intake.

To reduce this, balance the feed by introducing hay and using strip grazing methods. If required, dietary supplements like poloxalene can be introduced to further reduce the risk.

While cover crops offer numerous benefits, understanding their risks, especially in changing seasons, is a must for livestock safety.

Photo Credit: gettyimages-r-j-seymour