The aim of this study was to evaluate the efficacy of methyl-formamide in ram semen cryopreservation. The semen pool used in this experiment was obtained by artificial vagina collection from four mixed breed Santa Inês rams, around four years of age. Semen collection was performed once a week, during six weeks. Each week corresponded to one experiment replication. The semen pool was divided in five fractions in order to be diluted in one of the following freezing media: (1) tris-egg yolk with 5.3% of glycerol (TG5.3G); (2) tris-egg yolk with 3% of methyl-formamide (TG3MF); tris-egg yolk with 5% of methyl-formamide (TG5MF); tris-egg yolk with 7% of methyl-formamide (TG7MF); tris-egg yolk with 9% of methyl-formamide (TG9MF). Semen progressive motility, vigor and thermoresistance were evaluated. The treatments TG5.3G (50%) and TG3MF (38%) showed higher progressive motility after thawing, while TG5MF (29%), TG7MF (1%) and TG9MF (6%) showerd lower motility. Freezing media containing methyl-formamide were less effective in preserving spermatozoa membrane integrity and morphology than control media. In TG7MF and TG9MF extenders, less than 60% spermatozoa showed normal morphology. After thermoresistance test, semen cryopreserved in TG3MF showed vigor (2.6) and motility (15%) statistically similar to TG5.3G media (15% and 2.8, respectively); however, the extender TG5.3G was more effective in preserving plasma membrane functional integrity. In conclusion, in the experimental conditions used, glycerol showed more cryoprotectant potential than methyl-formamide.
Amide; glycerol; ram; tris-egg yolk