Pasture Pest Spotlight:
First Frost Brings Toxicity Concerns
With the first frost of the year quickly approaching, we need to be on the lookout for potentially dangerous plants for our livestock!
The main grasses in question are sorghums, sorghum-sudangrass crosses, and sudangrass. The greatest danger seems to be after a drought or a series of frosts; the grasses with the highest potential for problems are the forage sorghum varieties and less so with the sudangrasses. The type of grass is not the only critical factor; the fertility of your soil may also affect the chances of prussic acid poisoning. Those soils that are high in available nitrogen and low in phosphorous tend to be the most problematic.
A few weeks rest between freezing and grazing reduces the risk of poisoning because the cyanide release levels have time to decrease. When plants grow and become mature, the risk is also reduced since the higher levels are seen in the leaves of the plant, rather than the stalk and stem; times of stress (drought or frost) increase the potential of toxicity in plants, even mature ones. On high-risk forage, toxicity will take its toll before you even have a chance to figure out your animals are sick.
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