I know, with a bunny, you just put like 3 litter trays in there pen. And then find out which corner they like to go to the bathroom in (As they always pick one) and then put the litter tray there. Then sometimes they will pick another corner and put a diffrent littler tray in the corner. Aslo I put hay in the litter boxes as a munchy snack, they love it. This has always worked for me and my 2 bunnies! Good luck in traing your piggies and let us know how it goes!

Ash