Soy Infant Formula Powder Grocery Store RattyRat's Review: If you have a sick rat, or a rat that can't eat solids, or a rat that needs to gain weight, this is a wonderful product to use. Any brand "infant" soy formula will work, but it has to be soy! This provides COMPLETE nutrition for your rat in a simple powder that you mix with water. We usually mix one part powder with one part water, but you can also make it thicker to try and get more calories into your rat, or thinner and more watery if your rat is dehydrated. We usually feed our elderly rats, that can't eat solids, 1/2 a scoop of powder four times a day. Do not use the soy milk you find in the vegitarian section that is used as a milk substitute for adults. This is not nutritionally complete. You can also use things like Ensure or Boost (adult diet drinks), but they are harder to store and work with, because they go bad quickly after you open a bottle. Though they are a nice alternative if your rats don't like, or stop eating the soy. Along with this soy milk, try and get your rat to eat some of the fruit/veggie baby foods as well.