Barracks are supposed to give +2XP to Animals too, but it dont give them to Canine
But yes, my bad for Enclosure and Carnival, I forgot Pack Mule is not Animals...
What I mean is : the fact that these building allow the construction of Shearing Barn is totally hidden. Yes, they allow it, but it's notre written in the Sevopedia or when you build them.
Normaly, when a building allow he construction of another building, it have in the description "Required to Build X, Y, Z". e.g. Shaman Temple or Sewer System
Here, nothing like this
So, when you look at your list of building, you dont know that building this will allw you to build the Shearing Barn.
And maybe, the AI dont know it too...