This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
The Sorghums are important forage plants and are wholesome under most conditions. In certain cases, however, they develop hydrocyanic or prussic acid, a most deadly poison. Literature on the subject records many cases of sudden and violent deaths. One example given by Glover and Robbins will serve for illustration: "At Brighton, Colorado, thirty-two cows, after being kept in the corral over night, were turned into a field of Kaffir Corn of not over two acres. . . . Twenty-one of them were dead in half an hour, and four of the others were badly affected."
Examples and Conditions of Poisoning
The formation of hydrocyanic acid is due to the action of an enzyme on a glucoside, which resembles that found in almonds. Neither the glucoside nor the enzyme is in itself poisonous. The enzyme is especially active when green sorghum is wilted, and the poison is said to be more plentifully produced in stunted plants, or those of second growth. When the Sorghum has been dried there is no danger, hydrocyanic acid being very volatile, and the enzyme responsible for its formation being in all probability destroyed by the drying.
The symptoms produced are very striking. Hydrocyanic or prussic acid is the most rapid poison known. Even the dilute form found in these plants causes symptoms in a few seconds, especially when taken on an empty stomach. The animal becomes giddy or staggers and falls. Heart action is slowed and breathing laboured. Spasms and twitching of the muscles are followed by numbness in the limbs, and finally by delirium and death. Bloating is sometimes observed in sheep and cattle, but is not always present. If only a very slight amount of the poison has been eaten the symptoms are less pronounced. Sorghum has, however, been known to become so poisonous that a few mouth-fuls eaten on an empty stomach would kill a cow in ten minutes. An autopsy shows no pathological conditions but an analysis of the stomach contents of animals lately killed reveals the presence of hydrocyanic acid. The peach-like odour of the poison is usually quite noticeable.
Treatment is in most cases useless where any considerable amount of the poison has been ingested. The animal should be placed with head raised, and, if possible, in the shade. If bloating occurs in cattle the paunch should be punctured, a handbreadth in front of the hip bone. Injections of atropin sulphate serve to keep up the heart action. Sugar renders the poison inactive, and large quantities of corn syrup or molasses have been given with benefit. Treatment similar to that used for prussic acid poisoning in cyanide works is also recommended. One ounce of sodium carbonate (washing soda), and one-half ounce of copperas, each dissolved in a pint of water, should be kept on hand in separate, tightly corked, glass bottles. The solutions are mixed, and the mixture is administered at once. A quart is sufficient for a cow and one-half pint for a sheep. Sudan Grass, Sweet Sorghum, and Kaffir Corn are varieties that have been found to produce death, and great care should be taken in feeding these as well as the other Sorghums. The Sorghums are stout, broad leaved, annual grasses, ranging from three to fifteen feet tall, and have been introduced into this country as forage plants and for their seed. The large flowering panicles of different varieties vary greatly in shape. The spikelets are in pairs at each joint of the slender rachis, and the seeds are large, rounded and polished.