You certainly can feed your mice before feeding them to your snake. Mice enjoy seeds, such as budgie mix, mice lab blocks made for growing/breeding mice works great too. OR you can just feed a high fat/protein dog food that doesn't contain any dyes, and add the seed mix for variety. It will take a few days or a couple weeks to get the mice nice and plump, depending on how young/skinny they currently are. Keep in mind you don't just want a fat mouse, it will only make your snakes fat...pretty much the difference of us eating a nice healthy meal or a greasy fast food burger.
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