The methodological variants using toluidina blue (AT) to establish a trustworthy protocol for the computational analysis of chromatin condensation of rooster spermatozoa were studied. Twenty semen samples were used: ten from 35-week-old roosters and ten from 60-week-old roosters. Different methods of denaturation and staining were tested. The best method was hydrolysis with 1N HCl for 10 minutes, staining in bucket with 0.025% AT, pH 4.0, for 20 minutes, dehydration in alcohol, clearing in xylol, and mounted with Canada balsam. All the semen samples were submitted to this protocol and later evaluated by computational image analysis. Area, length, width, perimeter, and chromatin compaction homogeneity of head spermatozoa were measured. The sperm of older roosters presented more chromatin changes than the ones of younger ones. The spermatozoa of younger roosters presented bigger heads than the ones of older roosters. The computational analysis of chromatin compaction showed to be less subjective and more precise than the visual evaluation for identification of chromatin alterations of rooster spermatozoa.
fowl; toluidine blue; DNA condensation; fertility; image analysis; morphometry