HOW TO INSTALL:
-Download the file directly or with the mod manager. IF you've downloaded it directly then extract the file and place it into your (SteamApps\common\Valheim\BuildShare\Builds) folder.
-Look for the build named "Mutli_Breeder" in your build list.
-Toggle to view the build before placing it so that you can rotate it to fit your base.
-The focus point is on ground level just in front of the first set of support beams below the stairs.
-Make sure to flatten the area that you will be using for the breeder with the beams below as they are 6 tiles below and thus will not hinder the breeding process. 

GETTING ANIMALS INSIDE:
-This part requires some work, please see the screenshots for the steps below.
-First you'll need to build a ramp up to the back of the breeder.
-Remove the two full and two half wall sections as well as the beams I used for the snap points (replace them after both animals are inside the breeder)
-I'd recommend building a rail on the sides to keep them from falling off while you're pushing them up (if you have a harpoon it would make this a bit easier)
-To prevent the animals from walking down the ramp snap beams across to close the pathway as you're making your way up.
-Only try to get the animals inside the breeder after you have both of them at the top and have snapped beams in place so they can't go down again.
-Once you have them both inside remove the floors that connect to the breeder(this prevents them from walking back out)
-Remove the temporary ramp you built as you're making your way down it (careful not to fall)
-Build your staircase to access the chests at the top to replenish their food when needed (the reason there aren't stairs leading up from the ground is because I had originally built it into raised terrain on at my base, the iron beams were added after the fact because some players would not have their base the same as mine)  

PLEASE NOTE:
- To feed the animals I'd recommend downloading and installing the (AUTO FEED) mod as I've placed iron chests above the pen for the animals to eat from (no need to struggle with throwing food at a specific angle to only miss completely or have one of the animals not be in range of the food you managed to drop at their feet)
-Moving forward I may make some tweaks to the build like adding a staircase and possibly a roof too.