Last week I discussed the issues with ruminants grazing certain summer annuals after a frost or even a drought but not how it happens. The culprit is cyanide poisoning. Cyanide, prussic acid, hydrogen cyanide or hydrocyanic acid poisoning are all terms describing the same condition.
This is also the same reason they should not graze wild cherry leaves.
A number of common plants, including sudangrass, johnsongrass, sorghums and sorghum-sudangrass hybrids contain cyanogenic glycosides in the outer cells of the plant. Further inside the leaf tissue are the enzymes needed to convert these compounds to the cyanide poison.
When the plant undergoes a stressful event such as cutting, wilting, freezing, drought, crushing, trampling, chewing or chopping, the plant cells rupture which allows the cyanogenic compounds and the enzymes to combine and produce hydrogen cyanide gas. Ruminants also have enzymes in the rumen capable of converting the cyanogenic compounds in the plant into cyanide.
The toxic gas goes to the bloodstream and blocks a necessary step in the release of oxygen from red blood cells. The animal essentially dies from lack of oxygen.
Clinical signs of cyanide poisoning can occur within minutes to hours after consuming the toxic forage.
Usually the affected animals are found dead but, if observed early, may show rapid, difficult breathing, frothing at the mouth, muscle tremors, staggering and then collapse.
The mucous membranes (such as the gums) are bright pink and the blood can be a bright cherry red color.
Last week I mentioned that there is now a way to test a sample for cyanide. We have the kits in now so if you’re unsure or curious about a stand of forage we can do a simple test to see if it is present. Basically all we need is a good big handful of the forage in question. Call us at 695-9035 before you bring it in or if you want me to come out and test it for you.