Although most poisonous plants are dangerous throughout the year, or growing season, many are most dangerous during certain seasons. Animals Poisoned The most dangerous plants are usually poisonous to all livestock, but occasionally only poultry or swine or cattle may be affected by a particular species. Some animals, by nature of the way they eat, may graze a particular plant or plant part that is unavailable to other animals. Also, because of physiological differences among different kinds of animals, a plant may be readily grazed by deer, for instance, but be poisonous to cattle or horses. These are quite variable and are usually not specific for particular plants.
Early diagnosis is important in controlling losses by poisonous plants.
In cases of suspected poisoning call a veterinarian as soon as possible, and move the livestock from the area where the poisoning occurred. You should survey the stock often to catch symptoms early while a remedy may still be possible. However, most of the damage may have been done by the time the sick animal is discovered, and too often poisoning is only noticed after the animal has died. Abortions in livestock are often caused by an animal eating some poisonous plant in sufficient quantity to cause abortion but not enough to kill the animal or even cause outward symptoms. Abortions in cows have been caused by Gelsemium , Phytolacca , Cicuta , Conium , and by nitrate poisoning.