Would you be breeding them as pets or as feeders?
I have kept guinea pigs as pets and they have pretty specific dietary requirements. They need access to Timothy hay on a daily basis, need supplemental vitamin C on a daily basis, fresh vegetables such as carrots or celery, and they are most definitely "eating/pooping" machines. In addition, like another poster mentioned, they are quite vocal with loud "wheep wheep" sounds among many others.
Although I've not bred them, they are unique (compared to the mammals we generally discuss here) in that their babies are born furred, open eyed, and ready to go. I am pretty sure I'm correct in the statement that they have litters of four or fewer.
They are definitely cute, although personally I don't know that I'd have one as a pet again.
Hope this helps.....
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Rebecca
TSBabe66@hotmail.com
Honored to moderate at Snakefeeders, a great place to buy/sell/trade feeder animals. Come check us out! http://groups.yahoo.com/group/snakefeeders/