Some variability factors in the cytomorphological analysis of frozen bull semen.

Frozen bull semen was analyzed after fixation with glutaraldehyde (0.2% sol. in PBS) by clear field microscopy (after staining with Rose Bengal and Victoria blue B), phase contrast microscopy and differential-interference-contrast microscopy performed by two observers who analysed sets of 100 and 200 spermatozoa. The results obtained with phase-contrast microscopy did not differ significantly from those obtained using interference contrast microscopy, performed by two observers on sets on 100 and 200 spermatozoa, concerning the following sperm abnormalities: abnormal detached heads, acrosome ruptures, tail abnormalities and total abnormalities. In view of the importance of extending the evaluation of sperm cytomorphology among artificial insemination centres, and the fact the phase-contrast microscopy system is less expensive than a differential-interference-contrast system and easier to operate, the authors recommend the use of phase-contrast microscopy for the routine study of sperm cytomorphology.