Can I mix Gerber rice cereal into kitten formula?

I have two orphaned kittens that I have been bottle feeding. Don't worry, I have everything I need for raising kittens, but I'm starting to ween them soon and I was wondering if I could mix in some Gerber baby rice cereal into their formula to thicken it up a little? I tried mixing canned kitten food into the KMR and it made them a little constipated, so I was wondering if the rice cereal would be a little more mild approach to start with. I know cats are carnivores and that it might not be necessarily nutritious for them, but would it be BAD for them in any way?