The results from the insemination of frozen-thawed bull semen approach or equal those expected from natural mating, and contrast with the poor results obtained using frozen-thawed ram semen (Emmens & Robinson, 1962). Healey (1969), describing the ultrastructural changes in spermatozoa resulting from freezing, noted differences between species in the degree of acrosomal deterioration.
This report summarizes the results of experiments on the cooling and deep-freezing of ram and bull spermatozoa. The degree of change in the acrosomes was estimated by means of light microscopy after the specimens had been stained with Giemsa, using the following scoring system: 0, normal acrosome; 1 and 2, stages of acrosomal damage; 3, acrosome entirely lost. A typical spermatozoon in each of the categories is shown in Text-fig. 1.
Ejaculates from fifteen bulls were examined in one experiment and from twelve rams in a second experiment. Semen was diluted tenfold at 30° C and
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