Plan grazing operations accordingly. Drought Drought-stricken plants contain mostly leaves and are slow to decrease their potential for prussic acid production. Grazing stunted plants during drought is the most common cause of poisoning of livestock by prussic acid-producing plants. Frost Plants that are frozen may release high concentrations of prussic acid for several days. After wilting, prussic acid release from plant tissues will decline.
Dead plants have less free prussic acid.
Do not graze or green chop for several days after a killing frost. When only plant tops have been frosted, new shoots may regrow at the base of the plants. These can be very dangerous because of high prussic acid glycoside content, and because cattle will selectively graze them. Do not graze frosted summer annuals until regrowth of shoots is 15 to 18 inches tall, or until several days after the entire plant and shoots are killed by subsequent frost. Pasture To reduce danger from poisoning, do not graze sudangrass and sorghum-sudangrass hybrids until they are 15 to 18 inches tall, and several feet tall for forage sorghums.