FragOut! is a Half Life 2 multiplayer mod, in which you only get different kinds of grenades to fight with, instead of the usual weapons. Forcing players to adapt at using only throwing weapons new tactics are sure to arise!
Like the "Eat us" suggest, you can eat these animals to regain health!
They will sit around eating food or run around like a chicken without a head, it's all the mappers call or at least that's the plan... to allow mappers to chose animation of the animals, if they want to they can make them move if they know how to make stuff move :P so the animals won't have any AI, they'll be like healthkits but can't be blasted away.
The duck will heal 25 hp, the pig 50 and the cow is a super health pickup that will fully heal you.