Maple Toxicity in Horses

["guest@endurance.net" <guest@endurance.net>]

tomsites goearth@shentel.net
Hello,  a vet friend called me to identify a tree that had a downed wilted branch in a paddock where 2 horses died and 1 was not out of the woods yet.  Everyone knows that Red Maple (ACER rubrum) kills horses when injested in a wilted state BUT this was ACER negundo or Box Elder.  It was evident that this was the tree eaten from.  My Question??  Has anyone else had a horse injest Maple other than Red and come down w/problems??  Science is divided on this subject and the last information i've seen from the internet  said they have not even been able to identify the toxin.  If you have any information  as to sources on this matter could you please let me know.  thank you tomsites goearth@shentel.net