Breeding is not so highly recommended for guinea pigs, since they reproductive cycle is too short. Pregnancy period can only last within 65-72 days and the litter size (number of pups per delivery) ranges 1-6 pups. However, if you are ready for new born pups care, then we suggest that breeding should be done during their puberty stage (sexually maturity) which falls within 5-6 months old.
Your guinea pig's heat cycle lasts 16 days. She will only be interested in with the male guinea pig (boar) for about 8-10 hours during this time. Female guinea pigs get on quite well with this mating instincts, so the best way to manage the romance is to leave the your guinea pig together until you are sure she is pregnant.
Mating is dictated by hormonal changes which is explicitly shown during their reproductive cycles. In other words, it is a natural behavior. You can only intervene these mating instances if you don't want them to have pups or your are not yet ready for the incoming pups through neutering or cage separation.
For other related information, please visit and talk to our Pet Care Consultants in all our PLC outlets.
Eliezer M. Bauzon, DVM RN