I have both kd pine shavings and aspen. Originally I got two piggies and I almost immediately found out one was sick. I took the sick one to the vet and x-rays showed a blockage in her stomach. The pig came to me on a very poor diet of seed type rat food as they had run out of guinea pig pellets. The vet said the lack of fiber could have caused this blockage but this sick pig had been kept on Carefresh and now I'm very afraid the blockage may have been caused by eating the Carefresh. I have no proof and it may be a totally unfounded fear but I don't want to lose another guinea pig. Really, the blockage could have been caused by anything as far as I know. Maybe it chewed something left to close to it's cage, I don't know. I have since gotten another guinea pig as I want to keep two together. Maybe, in time, I'll give Carefresh a try. I know many, many people use it for chins, piggies, etc with no problem. I broke my heart to lose one of my guinea pigs so quickly and I don't want to lose another.