Yeah, I been digging around for what alot of the larger operations are using. I don't want wire bottom but I realized them on grass may not function long term. So figuring sand, straw and doing a fodder system so they'll have greens. I am very blessed with a boyfriend who father works in construction and has lots of left over supplies so I been expanding on potential pen designs that could be multi purpose like this:
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With the ability to put in dividers for breeders, or remove for grow out etc. I got till fall to get everything situated but I prefer to over research.