As cooler temperatures approach, producers should be aware of the dangers
As the first frosts of the season approach, it is a good time to reflect on information regarding the perils and precautions associated with prussic acid poisoning. Cattle are particularly susceptible to prussic acid poisoning which can be fatal.
The Basics
There are several species of plants and grasses that can be the source of prussic acid poisoning during different stages of growth and composition. Some of the plants to keep an eye out for are in the sorghum species; they include Johnson grass also known as perennial Sudan, Sudan grass, and sorghum Sudan. Additionally, plants in the prunus species such as cherry trees can also cause prussic acid poisoning.
“All of those have the potential to have cyanogenic glycosides which are sugars which have a compound that contains a cyanide group. And so, what happens is if a ruminant eats any form of the sorghum or prunus species it can release cyanide because of the microbes in the rumen. So, ruminants are especially susceptible,” Tim Evans, DVM, Ph.D., veterinary toxicologist with the University of Missouri, said.
Timing Risk
The grasses and plants in the sorghum and prunus species possess higher levels of cyanide when they are in an immature growth stage, typically 24 inches or less. The grasses and plants also contain elevated levels of cyanide if they are damaged. For example, if a cherry tree branch breaks during a storm and cattle eat the leaves. Or if cattle trample immature Johnson grass crushing the grass stems before consuming it.
During this time of year, the threat also comes after a non-killing frost. “When we start to have frost conditions it doesn’t necessarily even have to be the short Sudan grass, sorghum Sudan or Johnson grass. If you get frost damage, any of those plants, especially the prunus species and their leaves, can potentially release or have the cyanide more readily available,” Evans explained.
Prevention
There are steps producers can take to keep their animals safe. Wait to turn out cattle in pastures with potentially harmful forages until those grasses are 2 feet taller or more. After a non-killing frost do not let cattle graze the sorghum species for 14 days. Though some producers prefer to wait seven to ten days, Evans recommends two weeks just to be safe. Prussic acid poisoning can be fatal and happen quickly, so extra precaution is preferred.
After a killing frost, animals can return to the pasture after a week. When it comes to hay, forage specialists recommend waiting two weeks after cutting and baling sorghum species before feeding it to cattle. This will give the cyanide time to dissipate to non-toxic levels.
Lastly, refrain from moving hungry cattle into a pasture full of sorghum grasses. Fill up the animals with hay or other forages first and only turn in a portion of the herd. “If you are putting your animals onto new forage. I always recommend that people gradually introduce them to new forage. I recommend that the animals be fed a little bit of grain as a good way to help them out as well. Slowly adapt them,” Evans recommended.
