All day, all night, no colic.
Of course I've only been doing it for forty five years so I may be wrong
Just turned all the show horses out, as the temperatures are rising.
The way to manage eating is to limit it by fencing, rather than time.
If you truly think your horse is in danger then put up an electric fence and limit the amount of grass to which they have access, not the time they have access to it.
A lot of people do stall at night due to flies etc and also, of course, marauders.
I have nothing larger than foxes to contend with and a long long hawthorn hedge with a tunnel inside it that flies do not get into.
You know your facilities better than we do but turning a horse out on good grass for a couple of hours is going to cause colic far quicker than turning it out all the time on acceptable grass- bolting lush grass will cause colic, grazing shorter grass will not
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