The effects of glycerol levels, equilibration times, and their interrelationship with bulls on the ability of bovine semen to survive the freezing process

In the past few years, artificial insemination has become one of the most important tools that the cattle breeder has at his disposal to improve the quality of his animals. The artificial insemination organizations invest a considerable amount of time and money in locating sires. A portion of these bulls are rejected after semen test because of low fertility or a low rate of survival of spermatozoa during the semen freezing process. The loss of many valuable bulls and much time and money might be avoided if the causes of freezing failures in some bulls could be determined. With this in mind, an experiment was conducted to determine optimum glycerol levels, optimum equilibration times, the importance of their interactions, and to estimate the sources of variability in the ability of spermatozoa from different bulls to survive the freezing process.