Brain is perfectly okay to give as part of your other organ half in an organ meal every once in a while as it is very rich. Which yes, does mean it can cause some rather runny poos. Be sure to follow-up with a bone-in meal to help firm up poops again.
I second what Linda said. Brain gives really odd poops.
Ferrets: Contessa Kitties: Watson, Oskar DIP Sinnead, Vincent, Boris, Zeus and Athena, Willow, Mr. Frodo, Indie, Lucrezia, Judge, Odin, Miss Emily, Suki, Cody, Aristotle, Butterscotch, Frankenfurter. RIP Herne, Ligeia, and Mr. Stubbs