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namida, we do not recommend that people buy from pet stores under any circumstances. Most guinea pigs sold in stores are bred and raised in horrible conditions. No effort is made to keep track of who's impregnating whom, and there is much inbreeding. Sows are kept continually pregnant until they are too old to breed, and then they're killed.
If you're in an area that doesn't have guinea pig rescues, you should seriously consider getting another kind of pet rather than a guinea pig When you buy from a pet store, you participate in that chain of horrible breeding and sale of guinea pigs, and there's just no need to do that.