Commercial doses of frozen bull semen for artificial insemination may have a certain percentage of morphological defects, despite being subject to prior selection. The aims of this study were to determine the prevalence of morphological abnormalities in commercial doses (n = 55, r = 2) of dairy and beef bulls, from AI Centers and to determine the possible existence of differences between them, regarding the percentage of abnormal spermatozoa. At least 200 spermatozoa per sample were evaluated using Bengal Rose stain (3% m/v) and light microscopy (×1000 magnification). The mean percentage of abnormal sperm samples from dairy breeds was 7.19% ± 4.91% and from beef breeds was 15.83% ± 9.28%. Significant differences between biotypes were found in the proportion of abnormal spermatozoa, abnormal heads and abnormal midpieces; it could be due to different selection pressure. It was observed that the percentage of abnormal spermatozoa was not a good fertility level predictor for the commercial samples of frozen bovine semen used in this study. In both biotypes, the midpiece abnormalities were the most frequent, mainly its distal flexion (compensable defect). This could be as a result of the effects of freezing and thawing on spermatozoa.
Keywords: bovine biotype; conception rate; frozen semen; sperm morphology.
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