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 deg. 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 deg. to -79 deg. C. 24
Use of higher glycerol levels and storage at -20 deg. C. 25
THAWING 26
Comparison of thawing at 5 deg. C. and at 38 deg. 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 deg. 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
PRACTICAL FREEZING PROCEDURE 35
Collection of semen 35
Preparation of extender 35
Dilution after collection 36
Adding the glycerol 36
Equilibration 36
Freezing 37
Thawing 37