You do not, necessarily, consume biomass when infecting. If you wish to remove body parts like claws, fur, etc, then biomass can be gained. Improving olfactory ("scent") capabilities would require two kilograms of biomass, but allow for the ability to sniff out juicier materials to consume for the only matter that matters.
The Tic Queen quickly moves under the crack of the door and into what appears to be the back room/kitchen of the eatery. Spreading out rapidly the micro-colony of tics establishes themselves in several pantries. They would give birth later in the night and begin a steady stream of biomass-rich foodstuffs being transported back under the Queen's guidance.
With the acquisition of non-organic materials, biomass may by incorporated with them to dissolve, rework, and perform any other number of tasks. The more biomass used, the more of a material that might be incorporated (for example, three kilograms of biomass used in conjunction with a tin can might be able to produce a tin safety-shell around one of the Host-Rodents).
Seeing how small they are, one kilogram should cover the requirements.
Shortening the intestines on all three rodents leads to mild discomfort for each when relieving themselves, but their comfort is of no concern. Three kilograms of biomass are gained from the mutation, the rodents forced to endure.
Total Biomass: 3kg
Average Energy: Near-Full