Multiple ovulation and embryo transfer during the breeding season in Angora goats: A comparison of fresh and vitrified-thawed embryo transfer

This study aimed to assess the superovulation response and pregnancy rates of fresh and vitrifiedthawed embryos after transfer in Angora goats with comparing transfer at the beginning (BS) and end (ES) of the breeding season. Nine Angora goats were used as donors in both periods. Donor goats were synchronized and superovulated with the FSH and mated with five fertile bucks. At 156 hr following mating, embryos were collected surgically. Recipient Angora goats were divided into two groups at the beginning (fresh, n=15; vitrified-thawed, n=15) and end (fresh, n = 8; vitrified-thawed, n = 8) of the breeding season. Fresh or vitrified-thawed grade I embryos (early blastocyst/blastocyst) were transferred surgically to synchronized recipients. On the 30^th, 60^th and 90^th day of transfer, goats were examined by ultrasonography. The number of corpora lutea (CL), total oocyte/embryo and transferable embryos obtained in BS was found to be statistically higher than ES. On the 30th day of transfer, pregnancy rates were 73.30% and 75.00% in the fresh transfer groups in both BS and ES periods; while, rates of 20.00% and 37.50% were found in the vitrified-thawed group, respectively. The embryo survival rates of fresh transfers were 55.55% and 31.25% at BS and ES, respectively. The number of CL, total oocyte/embryo and transferable embryos in the BS was higher than ES following superovulation. Also, fresh embryo transfer can be successfully carried out during the breeding season in Angora goats. Moreover, although pregnancies were obtained following the transfer of vitrifiedthawed embryos, they did not sustain on the 60^th and 90^th days. So, further studies are needed for the vitrifiedthawed embryos.