EFFECT OF INITIAL FREEZING TEMPERATURE, ADDITION OF GLYCEROL AND DILUTION ON THE SURVIVAL AND FERTILIZING ABILITY OF DEEP-FROZEN RAM SEMEN

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G. COLAS
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Summary.

The influence of temperature, addition of glycerol, initial freezing temperature, method of dilution, level of glycerol in the diluted semen, equilibration time and type of diluent on the survival and fertilizing capacity of deep-frozen ram spermatozoa was studied. The fertilizing capacity of semen frozen according to the best conditions was compared with that of `fresh' semen.

The addition of glycerol at +30°C resulted in a highly significant decrease in the mean proportion of motile spermatozoa immediately after thawing compared with the effect of addition at +4°C. The immersion of the straws at -55°C significantly reduced the revival of the spermatozoa compared with initial freezing at lower temperatures. The exposure time to glycerol had no significant effect on the survival of spermatozoa after thawing and incubation, but fertility was significantly higher with 4% than with 2% glycerol. The I.N.R.A. diluent provided better sperm survival and a significantly higher conception rate than did lactose-egg yolk extender. The semen frozen according to the best conditions (about 50% of the samples) had a fertilizing ability similar to that of `fresh' semen when the proportion of motile spermatozoa before, and after 1 or 3 hr of incubation was equal to or above 45, 40 and 30% respectively.

 

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