Debbie,
At a place I volunteer, they had an issue with a horse that fell asleep in the crossties and they did say it was some sort of narcolepsy. They did ride the horse and he was fine as long as he was moving. It was just in the crossties that they had to watch him.
Have you consulted with a vet about this? Is it possible he is anemic? Perhaps he has some sort of thyroid problem. Does he have energy when you ride him?

Hi, Debbie:

Narcolepsy in horses is well documented now. I've known several horses with the condition. After a while they learn, if allowed, to "prop" themselves against walls/fences, so that they don't fall down when they fall asleep.

We had a nice little TB mare with the condition, and my Mum made her fleece lined anklets, so that when she fell down she didn't skin her ankles. I have a client with a TB mare who is narcoleptic as well. I have not known the condition to cause problems when riding, and usually the stimulation of grooming and tacking up negates any issues in cross-ties.

Do you leave him standing in the cross-ties alone? Do you leave him there while you go to do other things?

We never came across any treatment for the narcolepsy, in spite of both of my vets having attended a symposium dealing specifically with sleep disorders in horses (which, apparently, are myriad!). We have learned to keep the horses stimulated while we work around them, and have had no problems in that setting, and certainly no problems under saddle.

Hi Jan,
Thanks for the info. To answer your questions, yes I tend to leave him standing alone while I get myself ready to ride, for instance, boots, helmet, gloves on. I will certainly alter my routine and include activity/stimulation around him. No problem under saddle to date, anyway.

Hi Barbara,
Thanks for your input. Bloodwork did not reveal any deficiencies. Under saddle he is fine. Will keep him occupied while on the cross ties from now on and reduce his standing alone time...

Yes, I have had a similar problem many years ago. My pony used to fall asleep like this when she was being shown and had to stand still for long periods of time (like in the line-up in a halter class or hunter class). She would seemingly fall asleep and her knees would start to buckle.

I read about this recently in Equus magazine. Here's a couple links to get you started:

http://www.equisearch.com/horses_care/health/behavior/horse_sleep_d...

http://www.smartpakequine.com/health_and_nutrition/problems/sleepde...