I would see no reason why not. Probably not the most cost effective method but it will work.
Are the feeder guppies babies you have raised? It's not a good idea to buy feeder fish and then immediately feed them to your fish. If you want to do that, you should quarantine them first like you would any new fish, and make sure they aren't diseased before feeding them to your fish.
I know that and I buy all kinds of medicines for diseased feeders.