Comparison of different techniques to determine the percentage of intact acrosomes in frozen-thawed bull semen.
Twenty-seven different batch dates of frozen bull semen from 26 bulls were used in this study. The semen was in 0.5-ml straws, and 23 of the batch dates were in whole milk extender while 4 were in egg yolk-tris extender. Straws from each batch of semen were incubated for 2 hours in a water bath at 37 degrees C. Following this, the percentage of progressive motility, the rate of motility, and the percentage of intact acrosomes were determined for each unfixed sample. Each batch of semen was fixed in 2 different solutions of 0.2% glutaraldehyde in phosphate-buffered saline (glutaraldehyde 1 and glutaraldehyde 2) and in 10% neutral buffered formol saline (formol saline). The percentage of intact acrosomes for each sample in these fixatives was determined at Day 0 and Day 7. There were no significant differences in the percentages of intact acrosomes among the unfixed samples and the samples in the 3 fixatives at Day 0. At Day 7, the samples in formol saline had a significantly higher percentage of intact acrosomes than those in glutaraldehyde 2. When the percentage of intact acrosomes for the unfixed samples at Day 0 was compared with the percentages of intact acrosomes for glutaraldehyde 1, glutaraldehyde 2, and formol saline at Day 7, only the percentage of intact acrosomes for formol saline was significantly higher than for the unfixed samples. Only one of the batches of semen in egg yolk-tris extender could be evaluated in formol saline because of a heavy precipitate that formed. There was a significant interaction between extender and storage. For the whole milk extender, the percentages of intact acrosomes at Day 7 were higher than for Day 0 for all the fixatives used. For the egg yolk-tris extender, the percentage of intact acrosomes decreased from Day 0 to Day 7. The correlations between the percentage of intact acrosomes for the unfixed samples and the post-incubation percentage of progressivé motility and rate of motility were 0.65 and 0.46, respectively.
Richardson
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GF
Department of Health Management Atlantic Veterinary College University of Prince Edward Island 550 University Avenue Charlottetown, P.E.I., Canada, C1A 4P3.
Donald
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AW
Mackinnon
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CE