Thankfully, i've never had to use it, but I'm currently working at a ranch. The herbivore version is part of their emergency kit. Every rabbit owner i have talked about has said it is a must have for their emergency kits. Because it is made to have pretty much all the nutruents they needed.
Here, i found a picture of the back of the carnivore version. So, you can read what it is for.
Though it looks like you mught want to add water to make it soft and possibly dilute the protein.