CONTENTS

Page
[EARLY WORK ON FREEZING SEMEN][5]
[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]
[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]
[LITERATURE CITED][38]
[TEMPERATURE CONVERSION TABLE][39]
Urbana, IllinoisOctober, 1957
Publications in the Bulletin series report the results of investigations madeor sponsored by the Experiment Station

ACKNOWLEDGMENT

The authors gratefully acknowledge the financial assistance given to the Department of Dairy Science in support of these investigations by the Southern Illinois Breeding Association of Breese, Illinois, and the Northern Illinois Breeding Co-op of Hampshire, Illinois, through the Illinois Dairy Breeding Federation.