Two Cases of Suspected Poisoning With Goat's Rue (Galega officinalis L.) in Horses

•Horses are sensitive to goat's rue.•Galegine is heat resistant and Galega officinalis remains toxic in the hay.•14 g of dry goat's rue per day for three days is sufficient to cause symptoms.•Goat's rue poisoning in horses causes dyspnea that could lead to death. The present report describes two novel cases of suspected intoxication with Galega officinalis in 6- and 21-year-old Arabian mares displaying acute respiratory signs. Both animals showed signs of pulmonary edema at physical examination, with the oldest of the two also manifesting severe dyspnea and foamy nasal discharge. The mares were grazing on the same meadow with hay available ad libitum. Botanical analysis of the latter showed traces of the toxic plant Galega officinalis (L.), which has been daily ingested at a dose of around 14 g of dry matter for three days. Based on the respiratory signs and the presence of goat's rue in the mares’ feed, a presumptive diagnosis of plant poisoning was assumed. Dietary change and treatment allowed the 6-year-old mare to fully recover in 3 days while a longer period of about 2 weeks was necessary for the older horse. Horses avoid eating fresh goat's rue as its palatability is low, yet poisoning may still happen in these species when the plant is found in dried and processed feed material.