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PRESERVATION OF BULL SEMEN AT SUB-ZERO TEMPERATURES
By N. L. VanDemark W. J. Miller W. C. Kinney, Jr. Carlos Rodriguez M. E. Friedman
UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION
SELECTION OF SEMEN FOR FREEZING 6 Predicting freezability 6 Freezability of first and second ejaculates 7 Freezability of several consecutive ejaculates 7 Freezability of epididymal sperm 9 Freezability of washed sperm 10
EXTENDERS FOR FREEZING BULL SEMEN 10 Proportion of egg yolk in final diluent 10 Citrate level in final diluent 11 Storing and freezing diluent 12 Other diluents 13
DILUTION RATES 14 Effect of further dilution and refreezing 14
GLYCEROL ADDITIONS 17 Effect of glycerol on sperm survival at 5° C. 17 Glycerol levels for freezing semen 18 Rate, temperature, and method of adding glycerol 18 Allowing sperm to equilibrate with glycerol 20 Sugar additions and equilibration time 20 Substitutes for glycerol 22
FREEZING RATE 22 Effect of freezing rate on sperm survival 22 Rate of cooling in plastic and in glass 23
STORAGE TEMPERATURE 24 Storage at -23° to -79° C. 24 Use of higher glycerol levels and storage at -20° C. 25
THAWING 26 Comparison of thawing at 5° C. and at 38° C. 27 Thawing rate in plastic and in glass 29
EFFECTS OF FREEZING PROCEDURES ON METABOLIC ACTIVITY OF SPERM 30 Effect of glycerol additions on oxygen uptake of diluted semen at 37° C. 30 Effect of glycerol-plus-catalase on oxygen uptake of diluted semen 32 Effect of freezing procedures on oxygen utilization 33 Effect of freezing procedures on methylene-blue reduction time 33