I raised guinea pigs for a few year...could never imagine even a 3,000+ gram bp eat an adult guinea pig without potentially inflicting some damage upon itself...guinea pigs get huge, compared to rats, and I wouldn't even entertain feeding XL rats to the majority of balls I've seen. I've fed off quite a few newborn guinea pigs, which at that point they're already the size of a smallish medium rat. And as fast as baby guineas grow, it's only about 2-3 weeks tops till they become too large for most adult bp's.