Comparison of in vitro and in vivo fertilizing potential of buffalo bull semen frozen in egg yolk-, soya bean lecithin- and liposome-based extenders

The objective of this study was to compare different extenders for post-thaw in vitro sperm function and in vivo fertility of buffalo semen. Accordingly, sperm of 30 ejaculates extended in egg yolk (TRIS with 20% egg yolk; EY), two soya lecithin-based (SL-1; AndroMed (R) and SL-2; Bioxcell (R)) and a liposome-based extender (LS; OptiXcell (R)) were tested. The post-thaw semen was evaluated for computer-assisted sperm analysis (CASA), sperm viability, membrane and acrosome integrity, DNA integrity and acrosome reaction and first service pregnancy rate (FSPR) in a fixed-time artificial insemination programme. Total motility and VCL were the only CASA-based parameters that exhibited significantly higher (p < .05) percentage in LS among these extenders. Post-thaw percentage of acrosome integrity (55.9 +/- 1.4, 58.1 +/- 2.0, 55.8 +/- 2.0, 56.6 +/- 2.3) and DNA integrity (68.8 +/- 2.0, 69.2 +/- 2.3, 71.3 +/- 2.1, 69.1 +/- 2.1) did not differ (p > .05) in EY, SL-1, SL-2 and LS extender, respectively. However, a variable response in terms of efficacy of different extenders for sperm viability and plasma membrane integrity was observed. Assessment of inducibility of acrosome reaction showed significant differences between extenders (51.9 +/- 2.1, 44.3 +/- 2.4, 46.1 +/- 2.3 and 58.1 +/- 3.1%, respectively, for EY, SL-1, SL-2 and LS). Furthermore, field trials revealed significantly higher (p <.05) FSPR of LS-extended semen as compared to that for EY, SL-1 and SL-2 extender (46.3%, 41.2%, 31.2% and 29.7%, respectively). It is concluded that the liposome-based extender is more effective than egg yolk-and soya lecithin-based extenders and may be used for cryopreservation of buffalo semen in the future.