why animal product should not be used for vermicomposting

Vermicomposting is the breakdown of organic material by the joint action of microorganisms and red worms to convert it into useful soil conditioner. Because animal product contain too much oil or fat which can hinder the breathing  of the worms, as these worms breathe through their skin. Also adding more of animal product to the Vermicompositing mix  would increase the difficulty of maintaining low odour and healthy compost.