Chokecherry bushes had lethal levels of prunasin

Chokecherry bushes in the Northern Agricultural Research Center pasture where two local horses died last week contained a fatal level of a compound known to cause cyanide poisoning in livestock, the center's superintendent said Tuesday.

Gregg Carlson said lab results from Montana State University-Bozeman show that both samples of the chokecherry bushes taken from the pasture had levels of prunasin well above the amount considered potentially toxic. Prunasin releases cyanide when combined with water in the stomach of livestock.

Foliage containing between 600 and 1,800 parts per million of pruna...