Are there rules in print for Kroot of the animal variety, such as Kroot Hounds, Krootox, and Knarlocs? If nothing official, has anyone written anything up? Thanks for the help.

Nothing in the Rogue Trader books, and I do not beleive there are any in the Deathwatch books either, but I'll double check later. Hopefully we'll get a few examples in the Xenos book for DW that's coming in a month or two.

http://darkheresy.wikia.com/wiki/Beasts#Kroot_Beasts

About as good as you'll get for now, I'm afraid.

Thank you, gentlemen!