Lamb creep feeder size

[Agri]

I want to build a few for the lambs. One that they go into. What size would it need to be

 

[Al R]

I want to build a few for the lambs. One that they go into. What size would it need to be

Got any sheep round bale feeders? Turn them upside down and make a big circle with them.
the ewe below got through the round bale uprights but got stuck at the hips and then jammed her head in the lamb bars