478 Brief Communications J Vet Diagn Invest 15:478–480 (2003) Cyanide toxicosis in goats after ingestion of California Holly (Heteromeles arbutifolia)

Abstract. Cyanogenic glycosides are found in many native and naturalized plants throughout North Amer-ica. The glycosides themselves are not toxic, but they yield hydrogen cyanide (hydrocyanic or prussic acid) when they are hydrolyzed by b-glycosidases, either as a result of injury to the plant cells or by microbial action in the rumen. Hydrogen cyanide is readily absorbed from the gastrointestinal tract. Cyanide ion binds with iron in cytochrome oxidase, interfering with cellular respiration. The clinical effects are peracute, often resulting in death less than 1 hour after ingestion. This study describes a case that resulted in significant morbidity and mortality in a herd of goats after exposure to California holly (Heteromeles arbutifolia). Acute poisonings by plants containing cyanogenic glycosides are infrequently reported in goats. This is largely because of their browsing habits, which limit the amount of any 1 plant that is ingested. It is also likely that cases of acute death in goats are not eval-uated and go undiagnosed. Goats have been used as experimental models for chronic cyanide ingestion;10 therefore, their response to repeated subtoxic expo-sures has been well described. A clinical case of acute morbidity and mortality in a herd of goats after inges-tion of Heteromeles arbutifolia is presented. A backyard herd of 60 goats was maintained long-term on a diet consisting mostly of squash and cactus, and free access to a mineral block. In February 2002, after pruning what were believed to be olive trees, a neighbor donated the clippings that were subsequently fed to the goat herd. The clippings were later identified as H. arbutifolia. Within 4 hours of feeding, 3 animals died, and 7 were moribund. The affected animals were tachycardic and had marked jugular pulses. Mucous membranes were pale pink. No treatment was institut-ed in the affected, surviving goats. Field necropsies revealed multifocal hemorrhages in lungs and heart and congestion of the gastrointestinal tract. Kidney, lung, and liver were examined histologically from 3 animals. In addition, heart and abomasum were ex-amined from 2 of 3 animals and small intestine fro