Cryopreservation of guinea pig (Cavia porcellus) genetic resources : embryos production and freezing
The preservation of the guinea pig (Cavia porcellus) genetic biodiversity is important as a native source of protein for many highlanders in the Andean region and as a precious laboratory animal for biomedical research.The aim of this work was to establish the protocols that will enable an ex situ preservation of the genetic resources of this species by the female way.The necessary steps for the achievement of a cryobank project are:- the control of the embryo production thanks to hormonal treatments to synchronize the estrous cycles and to superovulate the females,- the cryopreservation in liquid nitrogen of the obtained embryos and their transfer into recipient females.A standard method for synchronization of heat periods based on the per os administration of altrenogest during 15 days has been defined. The heat periods of the females, donors and recipients of embryos, appears 4 to 5 days after the end of the progestagen treatment. Superovulation treatments, based on 3 injections at 24-hour intervals of hMG or 6 injections at 12-hour intervals of human recombinant-FSH, lead to an increase of the ovulation rate of about 3 to 4 times when compared to untreated females. However, the responses to the treatments remain variable and further studies involving a larger number of animals should be carried out in order to adjust the dose and the moment of application of the treatment.The slow-freezing method, using ethylene glycol as cryoprotectant, enables the attainment of a satisfactory in vitro embryo survival rate (70,3%). The vitrification method also gives good results, with a 41,7% in vitro embryo survival rate.The first successful transfer of fresh embryos into a synchronized recipient female has been achieved in this study. The transfers of frozen-thawed embryos did not yet lead to gestation.