make them from c c grids and tie them securley with the plastic ties you can get and make sure they have a top and they cant be moved and knocked about thats about as safe as you can get,
today max my old dog lie next to my girls in the conservatory as they dried after their baths, bless him should have got a pic, my 2 dogs have always been very good with my pigs because i alwasy fuss over them as well as the pigs so they dont feel jealous,