76 COMPUTER-ASSISTED SPERM ANALYSIS OF FROZEN SPERM MOTILITY AFTER DIFFERENT TIMES OF EXPOSURE AT 15°C

Abstract

One of the key factors for successful long-term cryopreservation in liquid nitrogen is maintaining the samples at –130°C or lower at all times to avoid cell damage (Barth 1991 Proc. 10th Ann. Conv. Am. Embr. Transf. Assoc., 20–26). Previous data indicated that exposure of the semen straw to ambient temperature for more than 15 s can raise the temperature above –130°C and reduce sperm motility, as determined by subjective evaluation (Berndtson et al. 1976 Proc. 6th NAAB Tech. Conf. Artif. Insem. Reprod., 51–60). The computer-assisted semen analysis (CASA) system provides an opportunity to assess multiple motility characteristics on a semen sample objectively and with high repeatability. An experiment was designed to evaluate the effect of exposing frozen semen in 0.5-mL straws to room temperature for 15, 30, 60, or 120 s on motility characteristics assessed by CASA system. Twenty-eight ejaculates from different bulls (19 Angus, 7 Hereford, 1 Brangus, 1 Shorthorn) were diluted using a chemically semi-defined media (Andromed, Minitüb, Tiefenbach, Germany) and frozen in an automatic freezer (Digicool, IMV, Paillette Crista, France). Five frozen straws per bull were used, one for each time of exposure and one as control (0 s = 0 time). Straws were exposed to room temperature (15°C ± 0.78) for different times and then placed back into liquid nitrogen. Semen thawing was conducted in a water bath at 37°C for 1 min. Motility characteristics were evaluated by the IVOS SpermAnalyzer (Hamilton Thorne Research, Beverly, MA, USA). Two chambers of 20-μm depth and 5 fields per chamber were analyzed (30 frames/0.5 s for each field). Seven motility parameters were evaluated: motile sperm (%), progressive sperm (%), VAP (path velocity, μm s^–1), VCL (track speed, μm s^–1), ALH (lateral amplitude, μm), BCF (beat frequency, Hz), and LIN (Linearity, %). The Kruskal–Wallis test was used to compare variables among groups, and results are shown in Table 1. There is a significant difference (P < 0.05) in the % of motile and progressive sperm when time of exposure was increased. There was a drastic and significant reduction in the percentage of motile and progressive sperm when exposure to 15°C was longer than 30 s. The live cells had similar motile characteristics: VAP, VCL, ALH, BCF, and LIN. In conclusion, sperm motility would be affected if straws are exposed for more than 30 s. More research should be done to test higher room temperatures, detect viability effects, and determine pregnancy rates after AI.

Table 1. CASA of frozen sperm motility characteristics at different times of exposure at 15°C

This research was supported by Centro Genetico Bovino Eolia S.A.