I wouldn't bother with stuff for fish, but for farm animal grade meds, I know a lot of people who've done it. The joys of going to an tech/ag focused college AND highschool. For what it is worth, I wouldn't try it becuase I don't know the meds well enough, even with the PDR at my side. The big thing would be concentration, not total volume, and the inactive agents. But honestly, when I took my first look at Paragon's STOMP, my first thought was that he'd gone through a farm supply place for quite a bit of it. (Right, wrong, doesn't really matter- still a damn good kit.)

That being said, instruments, dressings and the like are pretty much the same. Vetwrap is bulker than I like to carry, but it is nice stuff. And I'd bet money that a lot of the suture kits you find on eBay saw the inside of a feed store.