Poisonous native range plants

Plant poisoning is a common problem throughout North America, causing significant economic losses not only through death loss, but through the costs associated with reproductive loss, poor growth rates, herbicides, etc. Through good pasture management, recognizing toxic plants, and by understanding the effects of toxins on animals, plant poisoning can be largely avoided. Plants contain a variety of toxic compounds that help to deter herbivores and insects from eating them. A classic example of this is milkweed (Asclepias species) that contains a milky sap that is an irritant and therefore distasteful, and is also poisonous. Other compounds found in plants that may be toxic to animals are normal components of plants essential for plant growth. Nitrates and cyanogenic glycosides, for example, are found in a wide variety of plants and are essential in the formation of plant protein. Yet another reason some plants such as locoweed (Astragalus and Oxytropis species) are poisonous is that they have developed a mutually beneficial relationship with specific fungi (endophytes) that, when growing in the plant, produce a toxic alkaloid poisonous to horses and livestock.