128 Comparison of multiple maturation times on juvenile in vitro embryo transfer (JIVET)-derived oocytes and embryo development in the goat

Abstract

Juvenile in vitro embryo transfer (JIVET) is an assisted reproductive technology (ART) with the potential to produce numerous offspring from a single young female goat at 4 to 8 weeks of age. It has been reported in small ruminants that there can be a marked variable response to the administration of exogenous hormones for superovulation, the subsequent number of oocytes generated, and subsequent embryo developmental potential. The industry standard (as well as the recommendation of commercial media suppliers) in vitro maturation time is 21 to 24 h for conventionally derived oocytes. This study investigated multiple maturation times for JIVET-derived oocytes: 16, 22, and 28 h. Oocytes were collected from four JIVET animals at 6 to 8 weeks of age. The hormonal superovulation regimen used on the juvenile animals consisted of 4 × 40-mg FSH injections at ∼12 h apart and a 400 IU of PMSG injection given with the first FSH injection. Surgical recovery of the oocytes via a midline laparotomy was performed the day following the last FSH injection. All of the oocytes were collected via aspirating follicles that were 4 mm and larger. Oocytes with compact cumulus cells subsequently underwent IVM, IVF, and in vitro culture (IVC) utilising IVF Bioscience media and methods. A single straw of identical cryopreserved/thawed semen from the same buck was utilised for each of the IVF procedures. The results were (37/88) 42%, (37/85) 44%, and (39/91) 43% cleaved and (23/88) 26%, (24/85) 28%, and (28/91) 31% blastocyst rate based on respective maturation times for JIVET-derived ova. Development rate during the cleavage stage and blastocyst stage was analysed using a repeated-measures logistic regression model utilising generalized estimating equations (GEE), with maturation time as fixed effect and a compound symmetry within subject (juvenile goat) covariance structure. The main effect of maturation time on the odds of development during the cleavage stage (P = 0.8727) and blastocyst stage (P = 0.3857) was not significant. These results indicate that the time in maturation media does not have as profound an effect on development to blastocysts as a factor in the variability reported by other laboratories. The development rate of embryos from one juvenile goat produced very high blastocyst rates of (5/12) 42%, (11/12) 92%, and (11/15) 73%, respectively. Additional logistic regression analysis showed that the odds of development in this juvenile donor was significantly different compared with the other donors (pooled) during the cleavage stage at 16 h (P = 0.0083) and 28 h (P = 0.0021) maturation times. Likewise, the odds of development in this donor was significantly different than that of the other donors (pooled) during the blastocyst stage at 22 h (P = 0.0002) and 28 h (P = 0.0003) maturation times. This further indicates the wide variation of oocyte quality from JIVET-derived oocytes and indicates potential for higher development rates at 22 and 28 h in this specific goat.