137 EFFECTS OF X-SORTED SPERM IN QUALITY OF BOVINE BLASTOCYST DERIVED FROM IN VIVO-MATURED OOCYTES

Abstract

Recently, we reported on a promising system for selecting healthy IVF embryos in cattle using kinetics of early embryo development and oxygen consumption of blastocyst [Sugimura et al. 2012 PLoS ONE 7, e36627]. The present study was conducted to examine the differences in embryo quality of bovine blastocysts obtained after IVF of in vivo-matured oocytes with X-sorted and unsorted sperm. Holstein dry cows (n = 8) were reared under the same feeding and environmental conditions. Two ovum pickup (OPU) sessions were conducted in each cow to fertilize with or without X-sorted sperm. In vivo-matured oocytes were collected by OPU just before ovulation after superstimulation treatment. The oocytes were inseminated with 5 × 10⁶ sperm mL^–1 of each sperm, and presumptive zygotes were cultured in CR1aa supplemented with 5% newborn calf serum and 0.25 mg mL^–1 of linolenic acid albumin at 38.5 C in 5% CO₂, 5% O₂, and 90% N₂ for 168 h. Embryo kinetics were observed individually using a microwell culture dish (Dai-Nippon Print) and time-lapse cinematography (CCM-1.4MZS; Astec, Fukuoka, Japan; Sugimura et al. 2010 Biol. Reprod. 83, 970–978). Photographs of each embryo were taken every 15 min during the in vitro culture period and images were analysed by CCM-1.4 software (Astec). By assessing the quality of blastocysts, a combination of identified prognostic factors were used: (1) timing of the first cleavage (less than 27 h post-insemination); (2) two blastomeres at the end of the first cleavage; (3) absence of fragments at the end of the first cleavage; and (4) six or more blastomeres at the onset of the lag-phase. Data were analysed by ANOVA. In total, 34.1 ± 18.4 oocytes per session per donor were collected by OPU, and 23.7 ± 13.4 oocytes had an expanded cumulus cell. Oocyte recovery rates were recorded at 77.1 ± 15.1%. After IVF and in vitro culture, 10.6 ± 7.7 blastocysts per session per donor were produced in this study. There was no significantly difference in cleavage rates and blastocyst formation rates between X-sorted sperm and unsorted sperm (87.1 ± 10.8 and 82.6 ± 12.1% and 38.4 ± 23.6 and 57.1 ± 23.4%, respectively). However, blastocysts derived from X-sorted sperm showed significantly (P < 0.05) lower quality in the prognostic factor (1) and combined (1) to (4) than that in unsorted sperm (35.3 v. 54.0 and 14.7 v. 42.9%, respectively). Pregnancy rates were higher for the blastocysts that had a high score in the prognostic factors (1) to (4) compared to those that had a low score (75.0%, n = 8 v. 36.4%, n = 22). These results suggest that quality of blastocysts, based on the prognostic factors studied, derived from X-sorted sperm is lower than that from unsorted sperm.

Supported by the Research and Development projects for application in promoting new policy of agriculture, forestry and fisheries (22016).