Flow cytometric sperm sorting: Effects of varying laser power on embryo development in swine

This study was conducted to determine fertilization rate and embryo develop ment using the Beltsville Sperm Sexing Technology with two different laser power outputs, 25 and 125 milliwatts (mW). Freshly ejaculated boar semen wa s diluted; one aliquot was not stained or sorted (nonsort) and a second ali quot was stained with Hoechst 33342 and sorted as a complete population, no t separated into X and Y populations (all-sort). Ovulation controlled gilts were surgically inseminated with 2 x 10(5) spermatozoa (44-46 hr after hum an chorionic gonadotropin (hCG)) into the isthmus of each oviduct, one ovid uct receiving nonsort and the other all-sort at 25 or 125 mW. A total of 42 6 embryos were flushed from oviducts at slaughter 43 hr after laparotomy an d prepared for determination of fertilization and cleavage rates using conf ocal laser microscopy for analysis of actin cytoskeleton and chromatin conf iguration. The percentage of fertilized eggs and embryos was less for the 2 5 mW all-sort compared to nonsort or the 125 mW all-sort (77.9 vs. 96.3 and 96.2%, P < 0.05). The percentage of fragmented embryos was greater for the 25 mW all-sort than the nonsort (15.2 vs. 4.5%, P < 0.05), but did not dif fer significantly from 125 mW all-sort mean (7.2%). The percentage of norma l embryos (80.4% overall) did not differ (P > 0.05) among treatments. Howev er, the rate of embryo development was slower (P < 0.05) after insemination with the 25 mW all-sort spermatozoa compared to nonsort spermatozoa. Embry os in the 3-4 and 5-9 cell stages for the 25-mW all-sort and nonsort were 7 8 and 20% vs. 49 and 50%, respectively. The embryo percentages for the 125 mW (3-4 and 5-9 cell stages, 59 and 35%) did not differ significantly (P > 0.05) from the nonsort: or 25 mW all-sort. We conclude that the use of 125 mW laser power for sorting boar spermatozoa is advantageous to maintain hig h resolution separation and has no detrimental effect on embryo development compared to 25 mW. Mol. Reprod. Dev. 61: 87-92, 2002. (C) 2002 Wiley-Liss, Inc.