A sucrose-DMSO extender for freezing rabbit semen.

The aim of this study was to define a simple extender for freezing rabbit semen from selected males used to inseminate selected doses to obtain embryos for an embryo bank. Four experiments were carried out. In the first experiment, freezing extender was defined on the basis of the results of the post-thawing motility rate. Three factors and their interactions were studied: final concentration of dimethyl sulphoxide (DMSO) (1, 1.25, 1.5 and 1.75 M), egg yolk (0% of 10 v/v) and sugar (none, or 0.5 M of glucose, lactose, sucrose, or maltose). The sucrose and 1.75 DMSO improved significantly the post-thawing motility rate (sucrose 1.75 M DMSO extender: 42 +/- 3%). In the second experiment, this freezing extender was used to freeze semen from three lines. The post-thawing motility and normal acrosome rates were similar among the lines when the covariates, fresh motility and normal acrosome rates, respectively, were used in the analysis (52 +/- 1 and 66 +/- 1%, respectively). In the third experiment, frozen semen from the White New Zealand line (NZ) was tested by morphological normality and viability of embryos recovered. Recovery data from NZ does inseminated with fresh and frozen semen were compared. No significant differences were found in the number of normal embryos obtained per donor dose (8.9 +/- 0.5) and in their survival after vitrification (52% of live foetuses at 29 days of gestation). The sucrose-DMSO extender and freezing procedure used in this work can offer satisfactory results to apply in conservation and genetic programmes.