Comparison of two methods of extracting bull epididymal spermatozoa

Abstract

Extraction of epididymal spermatozoa may be necessary to avoid losing valuable genetic material, for example, from individuals of rare breeds or endangered species, but the resulting sperm samples may be of poor quality. Two methods of extracting bull epididymal spermatozoa from slaughterhouse material were compared. The bulls were 16–23 months of age. Spermatozoa were extracted by making an incision one cm in length in the tail of the epididymis to allow the spermatozoa to flow out (method A), or by flushing the tail of epididymis (method B). The two methods were used for each bull, alternating between right and left epididymis, i.e. if method A was used for the left epididymis in Bull 1, it was used for the right epididymis in bull 2, etc. Sperm concentration in the extracted samples was adjusted to 69 × 10⁶/mL in Andromed; the sperm sample was packed in 0.25 mL straws. After cooling for two h at 5 °C, the straws were placed 4 cm above liquid nitrogen for 20 min before transferring them to liquid nitrogen. Sperm motility, viability, reactive oxygen species, membrane integrity and DNA fragmentation were analysed in the fresh samples and again after thawing. The results for all parameters in fresh semen were not different between methods. Although sperm quality was lower in thawed samples than in fresh samples, there was no difference in sperm quality between the two extraction methods in the thawed samples. In conclusion, both methods are useful for the extraction of bull epididymal spermatozoa.