So I just wanted to say, I got the cattle Vit A for my mare with mild rain rot and runny eyes, who is on tested hay/pasture with all minerals balanced etc.... I had taken care of everything in her diet but didn't figure in the vitamin A!
I only gave 1ml... so 500,000 IU because I was scared to do a large dose. Then I ordered some Swanson Vitamin A (beta carotene) gel caps and added those to her food so she gets 100,000 IU per day from those. It's only been two days, but her eye is much less runny and brighter, and the rain rot is already clearing up.