115 FIRST SUCCESSFUL PREGNANCY AFTER EMBRYO TRANSFER INTO SYNCHRONIZED FEMALES IN GUINEA PIG (CAVIA PORCELLUS)

Abstract

The guinea pig (Cavia porcellus) has been used as a laboratory animal since the late 18th century and still remains essential in many research areas. It also plays an important role in the Andes societies as a source of protein for many low-income highlanders and as part of rituals and traditional medicines. Thus, the conservation of genetic diversity is a long-term issue that must be considered. To establish an embryo cryobank, it is necessary to develop a method of embryo transfer. Up to now no pregnancies after surgical embryo transfer into synchronized females have been reported in guinea pigs. The aim of this work was to design a standard embryo transfer method in this species. Eight normally cycling female guinea pigs from the Maria-Marcela Farm (Puente Piedra, Peru), weighing from 1 to 1.5 kg, were used in this study. Females were housed under farming conditions and fed on commercial pellets and tap water ad libitum. Three donor females were superovulated using 15 IU of human menopausal gonadotrophin (hMG, Massone^®, Buenos Aires, Argentina) and mated as soon as the vagina opened. Copulatory plug was observed and vaginal smears were taken to guarantee successful mating. Thirty-eight embryos were collected between Days 3.5 and 4.5 after ovulation at the morula and early blastocyst stages. Five recipient females were synchronized by a daily 0.1-mL dose of altrenogest (Regumate^® Equine, Intervet, France) per os by means of a syringe for 15 days. Two embryos were transferred into each uterine horn by laparotomy at Day 3.5 and 4.5 after ovulation. Two types of pipettes were tested for embryo transfer: pulled glass pipettes approximately 0.3 mm in diameter in 2 female recipients and plastic open pulled straws (OPS, Minitüb^®, Germany) in 3 recipients. Pregnancy diagnosis was detected by observation of no return to oestrus at Day 16 and confirmed by ultrasonography. None of the 3 OPS-transferred females were pregnant. One of the 2 pulled glass pipette–transferred females was diagnosed as pregnant and delivered 2 stillbirths (one per uterine horn). There were no postsurgical complications and the females undergoing embryo transfer returned to normal reproduction. We demonstrated that a classic surgical embryo transfer method is possible under field conditions to obtain pregnancy in this species. We suggest further studies using glass pipettes, which allow a more precise embryo deposition. Future experiments will incorporate the transfer of frozen-thawed embryos on a larger scale.