Yes! They do dissolve in water (they foam very slightly before dissolving completely)
I did take quite a large sample of the stuff, but am unsure about taking the rest back to the store, as it's not in the original bag ( I still have the original bag, but the feed was dumped into a bin after I got it). Will there be any problems with this? Or are feed stores ( UFA ) fairly lenient with returns like this?
Most folks do dump their feeds into a feed bin, so I would bag it back up into the original bag, if you still have it.
It doesn't matter if they want to take the bag back or not - take it back BUT:
There's a fine line when asking/demanding your money back in a situation like this. While you have to walk in with a "I am NOT happy about this" attitude, you still have to maintain a huge degree of being respectful and polite -- none of this was the fault of the store owner or the employees, unless they made the feed.
I've taken more than one bad bag of feed back, thru the years, and got my money back.
If there's a number on the original bag, call that number as they are the people you need to talk to. If there isn't a number, look them up on the internet; you'll find a phone number somewhere in Cyber space
If you don't get whatever that is analyzed before calling, I would certainly let the company know "it's in a ziplock bag, ready to be sent for analysis" and see what they say.
The more you "sound" like you know what you're talking about, while being firm, polite and respectful, the more attention the manufacturer will pay to you.
Be as polite as you can, no matter how much it kills you. Mom drilled into my head "you can catch a lot more flies with honey than you can with vinegar" That's been tough sometimes, but it does pay off