Comparison of the effect of two freeze-thawing curves for porcine semen. Preliminary results

Results obtained in fertility and litter size using frozen-thawed porcine semen are far from those obtained with natural service or artificial insemination of cooled semen. The objective of this study was to evaluate freeze-thawing of porcine semen comparing the traditional slow method to a rapid curve of temperature descent, using two cryoprotectants. Six males of proven fertility (n=6, r=2) were used. Semen was obtained using the gloved-hand technique and was transported to the laboratory at 17 ºC diluted in Androstar® plus. Samples were centrifuged 15 minutes at 800 g and re-diluted in: a) 5% dimethylformamide, 11% lactose, 20% egg yolk, 0.5% Equex or b) 3% glycerol, 11% lactose, 20% egg yolk, 0.5% Equex. The semen was frozen in 0.5 ml straws up to a final concentration of 300 millions sperm /ml using either a modified slow traditional Westendorff curve or a rapid curve. In both cases thawing was carried out at 37 ºC during 1 minute. Kinetic motility parameters were evaluated using a CASA system (ISAS v1, Proiser®, Spain). Sperm viability and acrosome status were evaluated using the FITC-PNA/PI stain. The results were analyzed using a factorial design (analysis ofvariance) with two factors, with two levels for each one and using the male as a blocking factor. No interaction was observed between the parameters. No significant differences (p> 0.05) were observed between curves or between cryoprotectants neither in any of the kinetic motility parameters evaluated nor in sperm viability and acrosome status. No significant differences (p> 0.05) were observed between curves or between cryoprotectants in sperm morphology in thawed porcine semen. Taking into account the results obtained, the rapid curve would be the practical choice as it is, faster and more manageable for fieldwork in any pig farm