Can anyone explain what the science is behind the dictum that you never feed a horse straight after exercise? I've always known that 'you just don't', but someone asked me why the other day and I was at a loss for answers.
According to vets advice: one should not feed immediatey after exercise because a) as said by CJ1 and b) circulation takes a while to return back from muscle work to organs e.g, stomach and intestine. Hence the cramps - or colic. One hour is reccomended. I don't spend all of my time with my head buied in a vet books but after travelling my mare once, gave her haylage and she promptly went in to colic spasms. I guess feeding hay nets whilst travelling is ok but not haylage - too much for stomach and hind gut to cope with. Solution - dont risk feeding - they've waited that long so another hour wont harm. Water - completely different story - can give immediatly after exercise as horse knows it has to replace lost liquid or else dehydration will set in.
Always_late is right but bear in mind how long you wait tofeed is dependent on how hard your horse has worked, if it's only gone for an idle hack or done some light schooling I wouldn't worry about waiting more than maybe 15 minutes before feeding it. If you've done quite intense work though, ie cross country galloping, endurance or hard jumping/ schooling then i would wait longer, at least ahlf an hour and more if it's sweating lots, after an hour you would definately be safe to give hard feed, whereas hay you could give much sooner, maybe after 15 minutes so long as you cooled the horse off properly once you finished working it. I generally ride my horse, cool him off, put in stable with some hay then do other jobs (clean tack, skip out, do waters etc), then feed him last of all before I go home so i know he's had a rest to recover after exercising.
PS: I used to work at a yard where all the horses were fed as soon as they got back after lessons and none of them ever suffered for it, but they didn't work that intensely in lessons so that's probably why.