Plant poisoning – an emerging problem in equine medicine?

Abstract

The incidence of plant poisoning in horses seems to have increased, but there are only a few reports discussing this issue. This study was performed to assess the number of plant intoxications treated in an equine clinic in Germany between 2011 and 2020 and to relate them to weather conditions (temperature, sunshine duration, precipitation). The analysis included a Poisson count regression. Forty-two cases were included. Plant poisoning roughly doubled in hot and dry years 2018 (n = 8) and 2019 (n = 9) compared to previous years. An increase of the average annual temperature by 1 ºC resulted in more than a doubling of intoxication cases relative to colic cases (IR 2.466, CI 1.52–4.98, p = 0.001). Longer sunshine duration resulted in a significant increase in cases (p = 0.013). Berteroa incana and Robinia pseudoacacia were the most common intoxicants. Climate change is a growing problem and leads to the overgrowth of plants that prefer warm and dry conditions, including poisonous plants, such as B. incana and Senecio jacobeae. If the grass on a pasture is scarce, horses eat plants that are normally unpalatable. Moreover, hay quality and its contamination with toxic plants might be an issue. Our hypothesis was confirmed as the number of plant intoxications in our region increased since 2018. Furthermore, our study tentatively indicates that weather conditions may influence the number of poisonings but also the species of toxic plants responsible for such poisonings. Awareness should be raised among equestrians that the number of certain plant intoxications threatens to increase in the future if climate change progresses. Further investigations are needed to test the hypothesis in a geographically wider area.