If you tame a Brahmin (for some reason), it will eat from the fertilizer station just like your other Brahmin. Also, it does not wander very far like other pets, I've learned. :
Brahmin not giving milk from brahmin pen? : r/fo76
Brahmin grill | Fallout Wiki | Fandom
Fasnacht brahmin mask | Fallout Wiki | Fandom
Fallout 76: Introducing the new brahmin meta... "Brahmin Launcher" - YouTube