Introduction: Rhamnus alaternus (RA) is an evergreen shrub from Rhamnaceae family, also known as “Mediterranean buckthorn” and growing around the Mediterranean Sea. Chronic consumption of its roots led to renal failure and rhabdomyolysis in a 58-year-old man in Tunisia [1] but literature about its toxicity remains scarce, especially on animals. Case history: In late January 2022, two 400 kg Aubrac heifers were found dead in their meadow in the south of France. According to the owner, both animals were in good general condition and, apparently, with no clinical signs before death. No clinical signs were reported in the other 3 heifers and 20 mature cows in the herd. A necropsy performed on one heifer revealed severe dehydration and a diffuse congestion of the serous and mucous membranes of the whole carcass. The entire gastrointestinal tract showed diffuse and marked congestion. In the abomasum, haemorrhagic foci up to 5 cm were present at the peaks of the fundic folds, the contents were pasty and greenish with some fibers. Multiple lanceolate, serrated leaves were found in the rumen which contents smelt a strong aromatic odour with a pH of 6,1. The leaves were identified as Phillyrea latifolia (PL), a non-toxic plant, and RA leaves which accounted, for this second plant, 6 g in a 600 g sample. The small intestine contained a small amount of greenish to reddish fluid and the colon, grey fluid with some fibers. The liver presented a mild hepatic cytolysis. The bladder contained yellow-green urine with a specific gravity of 1.010, a pH of 8.5, proteins and positive peroxidase activity. The epicardial fat showed petechiae and the endocardium multifocal suffusions up to 4 cm. Botanical analysis: As RA and PL are likely to be confused, a botanical analysis on site by a specialist was necessary to find and remove buckthorn and to estimate the consumption by the herd. The meadow, of 20 hectares and of dry grassland type, contains some groves of Mediterranean trees with shrubs. As this meadow cannot feed them, animals have at their disposal two racks with ad-libitum good quality grassland and alfalfa hays near the cow shed. There was storm and persistent heavy rains the day the two heifers died and were found 50 m near the only grove with RAs. The other cows in the herd had taken shelter in another grove. Diagnosis: In case of several sudden deaths in a herd, one main hypothesis is intoxication. The necropsy performed supports this hypothesis revealing diffuse congestion of the carcass. Presence of eaten buckthorn in the woods concurs with the leaves in the rumen of the necropsied animal. A diagnosis of RA poisoning was made. Discussion: Toxicity of RA is believed to be caused by the anthraquinones (AQ) contained in the plant [2], especially emodin [3]. Emodin can be found in humans’ urines until 12 hours after consumption [4], it is possible that urine emodin dosage could have been useful in the diagnosis of buckthorn poisoning. Several plants containing AQ are already suspected of hepatotoxicity [5], including Rhamnus species: Rhamnus purshiana [6] and Rhamnus cathartica [7]. In the present case report, necropsy revealed a mild hepatic cytolysis, so RA should also be considered as a hepatotoxic plant. Buckthorn, although considered poisonous, is widely used in herbal human medicine to treat jaundice [8] but after excessive use, a case of intoxication has been described, in a man [1]. Conclusion: RA is suspected to have caused the death of two heifers in France. To the authors’ knowledge this is the first reported case of animal poisoning with buckthorn. References: [1] Ben Ghezala et al. (2015) Case Rep. Emerg. Med. 182951; [2] Kosalec et al. (2013) Food Chem. 136, 335–341; [3] Brenes et al. (2022) J. Wildl. Dis; [4] Stolk et al. (1999), Pharm. World Sci. PWS 21, 40–43; [5] Posadzki et al. (2013) Clin. Med. Lond. Engl. 13, 7–12; [6] Garcia-Cortés et al. (2008) Rev. Espanola Enfermedades Patol. Dig. 100, 688–695; [7] Lichtensteiger et al. (1997), Toxicol. Pathol. 25, 449–452; [8] Elyebdri et al. (2017), Int. J. Pharmacol. Pharm. Sci. 11, 642–646.