Evaluation of motility and morphology of frozen bull semen under different thawing methods used for artificial insemination in North Shewa zone, Ethiopia

The frozen bull semen straws were gathered from three specifically chosen locations in the North Shewa Zone, namely Baso, Chacha, and Debre-Birhan town, and the laboratory work was carried out at the Debre Birhan agricultural research center. The researchers wanted to see how different thawing methods affected the mass motility of frozen bull sperm. The thawing protocols used for mass motility evaluation were 37 °C for 30 s, 35 °C for 40 s, 40 °C for 40 s, body temperature using a hand for 15 s and body temperature using a hand for 30 s by using a water bath. The mass motility of the frozen bull semen was evaluated subjectively using a phase contrast microscope with 10x magnification. The frozen straws were taken from six bulls and two breeds (Holstein Friesian and 75% Holstein Friesian). Motility, morphology, and storage time length of frozen bull semen were analyzed using the general linear model of SAS (9.0). The mass motility of spermatozoa varied from 31 to 41.6 percent in different thawing protocols. Among the thawing protocols, 37°C/30 s (thawing at 37°c for 30 s) was found to have a better motility percentage, which was about 41.6 percent of the frozen bull semen being motile. The frozen sperm cell motility using the 37 °C for 30 s thawing protocol from the national artificial insemination center was 47%, Baso 46.6% and Chacha 39.6%. There was no significant difference (p > 0.05) in the percentage of mass motility of frozen bull spermatozoa between Holstein Friesian and 75% Holstein Friesian cross breeds. There was no significant difference (p > 0.05) in the mass motility and morphology of frozen bull spermatozoa at different storage time length (58–204 days). The current study indicated that the major problems with low semen mass motility were thawing protocols which were used by artificial insemination technicians. Finally, the study recommended that thawing at 37 °C for 30 s had better frozen bull semen mass motility than other methods, so, artificial insemination technicians should use this recommended thawing method to have better frozen bull semen mass motility when they are doing artificial insemination (AI).