Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 7/22/2013
Publication Date: 7/22/2013
Citation: Daigneault, B.W., Mcnamara, K.A., Purdy, P.H., Knox, R.V., Krisher, R.L., Miller, D.J. 2013. Post-thaw motility of frozen boar sperm does not predict success with in vitro fertilization. Meeting Abstract. Society for the Study of Reproduction, Montreal, Quebec, Canada, July 22-26, 2013. Interpretive Summary:
Technical Abstract: Using cryopreserved boar sperm rather than liquid semen for in vitro fertilization (IVF) allows improved IVF consistency. However, cryopreservation of boar sperm results in reduced post-thaw motility, fertilization and embryo development. Boars are often screened on an individual basis prior to use with IVF based on sperm motility. Sperm that fall below an arbitrary motility threshold are often discarded. Our objective was to determine if categorization of boar sperm based on post-thaw motility was predictive of successful IVF. Semen from boars of different breeds was collected from commercial AI units and cooled to 15 °C for overnight shipment prior to freezing. Sperm from 16 boars were cryopreserved, thawed at 50°C for 20 sec, diluted in Androhep Cryoguard extender to 35 x 106 total sperm/mL and held at 37°C for ~ 7 min. Sperm motility was evaluated using light microscopy by averaging frames from 3 separate fields. Ejaculates were categorized based on total motility as good (40% or >), moderate (26-39%) or poor (16-25%). IVF was performed using each sample and was repeated in two to three independent experiments. A one-way ANOVA was employed using the MIXED procedure in SAS 9.0 to analyze all data and considered significant when P = 0.05. An average of 99 oocytes per boar was used for this experiment. Moderate motility sperm fertilized the most oocytes (73.0 ± 3.9%), and was higher than poor motility sperm (46.8 ± 8.4%) but not different than good motility sperm (56.9 ± 6.9%). There were no differences between poor and good sperm for the total percentage of oocytes fertilized. Moderate sperm had the highest percent of polyspermic fertilization (33.0 ± 3.4%), was higher than good (15.3 ± 4.5%) but not different than poor (18.3 ± 5.1%). No differences were observed among motility groups for monospermic fertilization. The percentage of cleaved embryos from oocytes seminated with sperm categorized as moderate in motility (65.0 ± 2.9 %) was significantly higher than poor (44.6 ± 3.1%) and good (51.6 ± 3.7%) motility groups. The same pattern was observed for blastocyst development in which moderate (20.4 ± 2.4%) was higher than poor (13.7 ± 2.5%) and good (13.2 ± 2.5%) motility groups. There were no differences between poor and good motility groups in blastocyst development and no differences among any groups in average blastocyst cell number. Interestingly, sperm categorized as moderate in motility had the highest rate of polyspermy but also the highest cleavage and blastocyst development. Furthermore, sperm categorized as poor in motility often produced fertilization and embryo development rates similar to good motility sperm. Our results indicate that post-thaw motility alone is not a strong indicator of fertilization and developmental potential when using frozen-thawed boar sperm for IVF. Sperm from boars with sub-standard post-thaw motility may be compatible for use with IVF whereas those with high motility may not always result in the best fertilization and embryo development. Furthermore, acceptable IVF rates were obtained with cryopreserved sperm that were cooled for shipping prior to freezing. Therefore, boar sperm with post-thaw motility as low as 20% can be cooled and frozen to achieve IVF success similar to that of good motility sperm. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2010-85112-20620 from the USDA National Institute of Food and Agriculture.