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

Abstract

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 100×106 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.