I've never heard of or seen Sulmet before, so is it like a liquid or mash??? Maybe try mixing it in with your chicken's favorite food...Usually chickens LOVE yogurt (if they've never had it, they will be cautious about it but once they try it they will probably like it), so maybe try giving some yogurt to them without the Sulmet (plain, non-flavored yogurt). When they get used to it and they seem to like it, mix some Sulmet into it without them seeing and give it to them.
If they don't like yogurt, mix it with something else that they may like.
I hope this helps!
If they don't like yogurt, mix it with something else that they may like.
I hope this helps!