Looks like Sheep Agent will let you store non sheep on it, although its possible the game would have said invalid move when I tried to confirm it, but I didnt want to confirm it because I didnt want to cheat. You can see me placing cows on it here:
I filed a bug report here: https://boardgamearena.com/bug?id=114505
I filed a bug report here: https://boardgamearena.com/bug?id=114505