I have not heard of baby food but in extreme cases where tube feeding is necessary I have heard of carnivore critical care being used. It is very rich in water and is easily digested. 18 months seems like a very long time but I have no idea of the animals status. I have seen critical care fed for 3-6 weeks for severely dehydrated very ill animals. The case I am thinking of was a rescue where a young BP was found in a house abandoned for a long period of time. Extremely emaciated, dehydrated, and fighting RI and mouth rot. The critical care allowed the animal to put some weight on and gave it a fighting chance, while the antibiotics kicked in.