I've had a couple of cases recently of laminitis being caused or exacerbated by eating privet. One wasn't too bad, but the other was quite a serious case (the horse got colic as well).
There's not much detailed info in the veterinary texts on the toxicity of privet other than that it is toxic. I can't find any mention of it causing laminitis, but it does apparently cause gastro-intestinal upset, which potentially could then cause laminitis. I was slightly surprised the horses were eating it so readily as it apparently tastes really bitter (didn't fancy trying it myself) - but I guess if the horse is hungry...
Anyway, I thought I'd post this just in case it helps someone get to the bottom of an unexplained case. It's easy not to pick up on that garden hedge that's adjacent to the field, etc.
I'll post this on a couple of other boards as well, but if anyone has access to appropriate boards that I don't, please feel free to cross post.