Measure from the top of her back at the shoulder to the bottom of her feet when she's lying on her side She needs enough room so she doesn't get her legs caught under the bar but has to lie down slowly to fit in the space, giving the piglets a chance to squeak and let her know they're there. I remember seeing a new commercial farrowing design which put a slope on the wall at one side, which had a similar effect - the sow had to slide down rather than just plonk herself.