55 EFFECT OF TREHALOSE FOR FROZEN–THAWED RAM SPERM MOTILITY PARAMETERS

Abstract

Computer-assisted sperm analysers have become the standard tool for evaluating sperm motility because they provide objective results for thousands of mammalian spermatozoa. Ram semen was collected using electro-ejaculation from 10 adult rams of Chingizskaya indigenous sheep breed. Motility was determined using computer-automated semen analysis (Hamilton Thorne Motility Analyzer, Beverly, MA, USA). Trehalose solution (0.375 M) was added to Tris-buffered saline solution to give the following trehalose extenders: 25, 50, 75, and 100% (vol:vol), and analysed for motility using computer-automated semen analysis. The sperm pellets were resuspended at 24°C in cooling extender – trehalose extenders of each concentration containing 5% egg yolk. The diluted semen was cooled to 5°C within 2 h. The semen was then further diluted 1 : 1 with freezing extender – each trehalose extender containing 1.5% glycerol to obtain a sperm concentration of 2.0 × 10⁸ cells mL^–1 – and then loaded into 0.5-mL straws. Straws were frozen using a programmable freezer with a freezing curve of 5°C to –5°C at 4°C per min, –5°C to –110°C at 25°C per min, and –110°C to –140°C at 35°C per min, and then the straws were plunged into liquid nitrogen for storage. Frozen samples were thawed in a 37°C water bath for 30 s and analysed for motility using computer-automated semen analysis. Statistical analyses were performed with a Student's test. The fresh semen samples showed the next results: motility 88.3 ± 2.4%, progressive motility 26.8 ± 6.9%, and progressive velocity 61.9 ± 4.2 μm s^–1. Motility of the frozen-thawed spermatozoa was 63.6 ± 2.9% (25% trehalose), 55.6 ± 5.2% (50%), 32.4 ± 4.7% (75%), and 23.6 ± 3.2 (100%). Progressive motility was 15.6 ± 3.9% (25%), 13.7 ± 3.7% (50%), 4.5 ± 1.3% (75%), and 5.2 ± 1.3% (100%). Progressive velocity was 93.5 ± 8.3 μm s^–1 (25%), 85.4 ± 8.1 μm s^–1 (50%), 65.7 ± 6.1 μm s^–1 (75%), 35.2 ± 3.3 μm s^–1 (100%). Motility of the frozen-thawed spermatozoa significantly decreased with increasing concentrations of trehalose in the extender (P < 0.05). These preliminary studies showed that further research is needed of use trehalose for ram spermatozoa cryoconservation.