My solution is called "I don't want my brother to have anything that I don't have"
Rowdy is a VERY picky eater and even when we had another older dog - Rowdy would not touch heart guard, even when I broke it into pieces and gave one piece to the older dog and then (tried) one to Rowdy. He just wouldn't buy it.
Then we got Rexy - and Rowdy is soooo competitive with Rexy - there is no longer any problem at all. Rexy will eat ANYTHING!!! So, when I give a piece of heartworm med to Rexy - Rowdy is chomping at the bit to get his bite. I'll swear - it's psychological!!!!! At least it works and there is no more heartworm med fights!