Hi, I have a hard keeper and she’s 24 appendix quarter horse mare. I feed her orchard grass and some alfalfa (she gets depressed if she can’t have her beloved alfalfa from Oregon) no less than 10lbs per feeding. She also gets 3lbs of triple crown senior feed and 8oz of ground flax seed. She gets regular deworming when necessary by fecal test (rarely have to worm) and sand clear every other month as she doesn’t typically eat on sand. If you’re having a fly issue I would try chia seeds over garlic. Garlic is toxic to horses, they’re not intended to eat it and wouldn’t naturally. I have noticed my mare doesn’t get swarmed with flies as much just being on flax seed. It may also be called Lin seed. I’ve never had any issues feeding my horses sweet feed or molasses based grains year round. I live in Southern California in high desert climate. 50s-60s in the winter and sometimes as hot as 100+ in summer but usually summers are in the 90s. I’ve never had a colic issue. Hope this helps!