With corn silage harvest coming into full swing, we have had some questions about harvesting poisonous plants with the forage or perhaps even with grain. A number of plants contain potentially poisonous substances that may be toxic to livestock if consumed. If you suspect livestock poisoning, call your local extension educator or veterinarian immediately. Once the poisoning has occurred, it can be very difficult to pinpoint the exact cause. Scouting fields and identifying potential poisonous plants prior to or during harvest can help avoid livestock losses. Some of the more common poisonous plants that we should pay attention to this time of year are:

Jimsonweed - The entire plant is poisonous (seeds are most toxic) - Poisoning symptoms includes thirst, mood swings, convulsions, coma, and death. The poisonous principles are solanaceous alkaloids -- 0.06 to 0.09% (dry wt.) equivalent of animal body wt. is toxic.

Milkweeds - The entire plant is poisonous - Poisoning symptoms includes depression, muscle tremors, spasms, bloat, difficult breathing. The poisonous principles are glycosides and galitoxin - 0.3 to 0.6% of body weight.

Nightshade species (eastern black, horsenettle, groundcherry, etc.) - Vegetation and unripe fruit are most poisonous and wilted leaves are especially toxic. Berry contamination in soybean grain is more of a quality issue resulting from staining and mold - Poisoning symptoms include loss of appetite, salivation, weakness, trembling, and paralysis. The poisonous principle is solanine - toxic at 42 mg/kg (LD50) = 0.1 to 0.3% of body weight. Solanine is reportedly destroyed by cooking, but ensiling probably does not reach a high enough temperature.

Pokeweed. - The entire plant is poisonous and especially the roots, shoots, and unripe berries; berry toxicity decreases as they mature - Poisoning symptoms include gastrointestinal cramps, weakened pulse, respiration, salivation. The poisonous principles are saponins, phytolaccine and alkaloid phytolaccotoxin and glycoproteins - 10 or more berries can result in toxicity to humans. This is unknown for livestock, but perhaps 100-200 berries/1000 lb animal.

Source: Bill Curran and Dwight Lingenfelter, Weed Science, Penn State