EFFECTS OF THE FREEZING RATE ON VIABILITY AND FERTILITY OF FROZEN-THAWED FOWL SPERMATOZOA

An improved method for the freezing and thawing of fowl semen was deve loped using glycerol as a cryoprotectant. The effect of the freezing r ate was observed on the motility, viability plus morphology of spermat ozoa and the fertility rate, as assessed on Days 2, 3 and 4 post insem ination. Overall 5 to 6 twice-weekly successive inseminations were per formed. In experiments 1, freezing rates of -1, -5, -10 and -15 degree s C/min from +5 to -35 degrees C, were tested for the above 4 paramete rs. The best results were obtained with freezing rates of -5 and -10 d egrees C/min. In Experiment 2, the freezing rates of -5, -7 and -10 de grees C were tested for the fertilizing ability of the spermatozoa. Th e best freezing rate was -7 degrees C/min. The fertilizing ability of pooled frozen-thawed spermatozoa was very promising (76% fertilized oo cytes.) We conclude that even without the selection of parent stock an imals (for fertilizing or laying ability) and without any selection of semen before freezing or after thawing, it is possible to obtain a hi gh level of fertility and viability with this improved glycerol method following twice-weekly insemination with 300 million sperm cells.