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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 6/1/2018 Publication Date: 4/11/2023 Citation: Stegelmeier, B.L., Davis, T.Z. 2023. Toxic Plants. In: Remillard, R.L., editor. Equine Clinical Nutrition. 2nd edition. Hoboken, NJ. John Wiley & Sons. 212-243. Interpretive Summary: Poisonous plants are found in nearly every plant community- in rangelands, cultivated pastures and paddocks, and even in cultivated fields. Some are native plants with established stable populations. Others are noxious weeds that can invade and dominate plant communities replacing native species and other nutritious forages. This invasive nature can also lead to contamination of fields where they can be included in baled forages, pellets, mixed feeds and grain. Additionally some commonly used forages can become toxic if used inappropriately; if they are improperly fertilized; or if they are stressed by drought or frost. Consequently, exposure to poisonous plants is common; however, poisoning is relatively infrequent. Poisoning occurs when animals eat a toxic amount of plant fast enough to develop disease. Under most grazing situations horses generally avoid eating toxic plants. However, if alternative forages are not available or feeding competition is high many unacceptable plants are eaten. Some toxic plants are palatable and therefore dangerous whenever animals have access to them. The objectives of this work is to review select poisonous plants with an emphasis on the plant communities and conditions in which they are likely to be eaten and cause poisoning. The following tables list select poisonous plants that are likely to intoxicate horses in pastures (Table 1), range (Table 2) and hay or prepared feeds (Table 3). As many plants affect horses in two or even all three sources, individual plants will be presented systematically and the source(s) identified. This is a select group of plants and several that have historically been included in such lists have been omitted as they lack evidence of poisoning in horses. Technical Abstract: Poisonous plants are found in nearly every plant community- in rangelands, cultivated pastures and paddocks, and even in cultivated fields. Some are native plants with established stable populations. Others are noxious weeds that can invade and dominate plant communities replacing native species and other nutritious forages. This invasive nature can also lead to contamination of fields where they can be included in baled forages, pellets, mixed feeds and grain. Additionally some commonly used forages can become toxic if used inappropriately; if they are improperly fertilized; or if they are stressed by drought or frost. Consequently, exposure to poisonous plants is common; however, poisoning is relatively infrequent. Poisoning occurs when animals eat a toxic amount of plant fast enough to develop disease. Under most grazing situations horses generally avoid eating toxic plants. However, if alternative forages are not available or feeding competition is high many unacceptable plants are eaten. Some toxic plants are palatable and therefore dangerous whenever animals have access to them. The objectives of this work is to review select poisonous plants with an emphasis on the plant communities and conditions in which they are likely to be eaten and cause poisoning. The following tables list select poisonous plants that are likely to intoxicate horses in pastures (Table 1), range (Table 2) and hay or prepared feeds (Table 3). As many plants affect horses in two or even all three sources, individual plants will be presented systematically and the source(s) identified. This is a select group of plants and several that have historically been included in such lists have been omitted as they lack evidence of poisoning in horses. |
