CRYOPRESERVATION OF RAINBOW TROUT SEMEN: DILUENT, STRAW AND THE VAPOR COLUMN

Abstract

The present paper concerns to the development of a simple semen freezing technique to be used in commercial systems. Fresh milt was obtained from two years-old adult males of rainbow trout. The samples were previously cooled (4°C), then diluted, packaged in straws, and frozen in liquid nitrogen vapor. The freezing system was composed by a 33 L Styrofoam^TM box with a graduated metal web; straws of 0.5 mL and 4 mL were tested and two types of extenders were used: V2e with 10% DMSO and modified Cortland solution with 24% DMSO. Two experiments were performed: the first one evaluated the effect of the extenders and straw type on the fertility of the frozen/thawed semen, and the second one verified the effect of the vapor column and straw position on the viability of the frozen/thawed semen, using 0.5 mL-straws and V2e extender. The sperm viability was tested by checking eyed eggs production. In the first experiment, there were no statistical differences (P>0.05) between the two tested straws and the modified Cortland solution. However, the V2e solution treatment showed a significantly higher fertilization rate when associated to 0.5 mL straw. In the second experiment, a remarkable statistical interaction (P>0.05) was observed between the straw cargo and vapor column (freezing point) effects on the percentage of eyed eggs.