I didn’t have any problems with my horses eating limited amounts of acorns until the time I noticed their manure was a strange orangey-yellow color. Caught it the first day and locked their gates to the acorn pastures. Later that day they acted crampy and mildly colicey so I’ve watched them more closely ever since that incident.
This is the time of year I’m glad I have plenty of squirrels and a few deer and maybe bears that come at night to eat the acorns.
And just this afternoon I spotted a flock of 12 Osceola Turkeys perusing my pastures and they’ll eat acorns also especially as it cools down and insects aren’t as plentiful.