Objective: Deep uterine artificial insemination (DUAI) was examined to improve pregnancy rate with epididymal spermatozoa in Hanwoo cattle.
Methods: The estrus cycles of 100 Hanwoo cows were synchronized, and the cows were used for insemination. Seventeen cows were inseminated by DUAI with epididymal spermatozoa, and 32 cows were inseminated by body of uterus AI (BUAI). As a control, 51 cows were inseminated by BUAI with frozen-thawed ejaculated spermatozoa from one bull. After 70 to 80 days of AI, pregnancy was evaluated by rectal palpation and ultrasound. Motility of epididymal spermatozoa were examined in DUAI and BUAI immediately after thawing, as well as at 3 and 6 h of incubation.
Results: The pregnancy rate of DUAI with epididymal spermatozoa tended to be greater than that of BUAI with epididymal spermatozoa (DUAI and BUAI vs. 58.8% and 31.1%, p=0.075). The control spermatozoa group showed a 56.9% pregnancy rate. The fast, progressive motility of the control group was significantly higher than in epididymal spermatozoa in DUAI and BUAI groups immediately upon thawing and after 3 and 6 h of incubation (p<0.05). VSL and VAP of epididymal spermatozoa in DUAI and BUAI at 6 h of incubation periods were both significantly lower than those in the control spermatozoa group (p<0.05). LIN and ALH of epididymal spermatozoa were low compared those at 6 h (p<0.05). BCF and hyperactivation of epididymal spermatozoa were lower than in the control spermatozoa group immediately after thawing and at 3 h (p<0.05). These motility parameters suggest that epididymal spermatozoa have low motility and fertilizability compared to control spermatozoa.
Conclusion: The DUAI method can overcome the low pregnancy rate of epididymal spermatozoa, even though epididymal spermatozoa have low motility and fertilizability. This method will contribute to improvement of pregnancy rate for genetically valuable and post-mortem bulls.