Relative efficacy of egg yolk and soya milk-based extenders for cryopreservation (−196°C) of buffalo semen

AIM The aim was to compare commercially available soybean milk-based extenders, viz. Bioxcell(®) and Optixcell(®) (IMV, France) with standard Tris-citrate-fructose-egg yolk-glycerol (TFYG) extender for cryopreservation of buffalo semen. MATERIALS AND METHODS Semen was collected twice a week in artificial vagina from six sexually mature, 4-6 years old, healthy breeding bulls of Surti buffalo breed. In all 48 qualifying ejaculates (8 per bull) having initial motility >70% were split into three equal aliquots and were diluted (at 34°C keeping 100×10(6) sperm ml(-1)) in TFYG, Bioxcell and Optixcell extenders. The French mini straws filled from each aliquot were gradually cooled to 4-5°C, equilibrated at 4°C for 4 h and frozen in liquid nitrogen 2 vapor using programmable biofreezer. Just before freezing (post-equilibration) and 24 h after frozen storage, the samples were evaluated for various sperm quality parameters using standard protocols. Frozen semen straws were thawed in a water bath at 37°C for 30 s. The post-thaw incubation survival (37°C for 1 h) was assessed through motility rating at 0, 30 and 60 min of incubation. RESULTS The mean percentages of prefreeze sperms in TFYG, Bioxcell and Optixcell extenders in terms of progressive motility (69.48±0.37, 68.02±0.49, 70.94±0.38), viability (79.21±0.39, 77.38±0.48, 81.58±0.38), total abnormalities (7.90±0.14, 8.60±0.16, 7.08±0.15), intact acrosome (89.54± 0.18, 88.58±0.22, 90.52±0.21) and hypoosmotic swelling (HOS) reactivity (67.96±0.32, 65.65±0.42, 70.23±0.37) varied significantly (p<0.05) between extenders. Similar pattern of significant (p<0.05) variations between these extenders for post-thaw sperm progressive motility (47.71±0.79, 44.38±0.85, 49.90±0.90), viability (57.19±0.79, 53.85±0.84, 59.67±0.91), total abnormalities (12.33±0.17, 12.75±0.21, 11.27±0.18), intact acrosome (76.83±0.23, 75.90± 0.27, 78.50±0.25) and HOS reactivity (45.02±0.84, 42.31±0.82, 47.81±0.90) was also observed for TFYG, Bioxcell and Optixcell extenders. The recently launched improved soybean milk-based extender Optixcell excelled the older Bioxcell extender and even standard TFYG in respect of some of the sperm quality parameters. CONCLUSION The advantages of soy lecithin-based bovine semen extenders over egg yolk regarding sanitary issues are unquestionable but still egg yolk-based semen extenders are widely used because of the cost factor and good in vivo fertility results.