INFLUENCE OF INSEMINATION-OVULATION INTERVAL AND SPERM CELL DOSE ON FERTILIZATION IN SOWS

This experiment was conducted to determine the effects of sperm dose a t insemination on fertilization rates and accessory sperm cells attach ed to day 5 embryos. Multiparous sows (n = 115) were artificially inse minated once with 1 x 10(9), 3 x 10(9) or 6 x 10(9) sperm cells betwee n 3 h and 48 h before ovulation. Transrectal ultrasonography was perfo rmed at intervals of 4 h to determine the time of ovulation and sows w ere killed at 120 +/- 5 h after ovulation to assess the results of fer tilization. The insemination-ovulation interval had a major influence on the fertilization rate and accessory sperm count. A nonsignificant but consistent increase in fertilization rate and in number of accesso ry sperm cells due to the sperm dose was observed. During the insemina tion-ovulation interval of 12-24 h, the median fertilization rates wer e 95%, 100% and 100%, and the median accessory sperm counts were 11, 1 7 and 31 for the 1 x 10(9), 3 x 10(9) and 6 x 10(9) doses, respectivel y. During the insemination-ovulation interval of 24-36 h, the median f ertilization rates were 88%, 95% and 97%, and the median accessory spe rm counts were 6, 8 and II for the 1 x 10(9), 3 x 10(9) and 6 x 10(9) doses, respectively. No direct relationship was detected between embry o quality and the accessory sperm count but there was a relationship b etween insemination-ovulation interval and accessory sperm count. The fertilization rate was positively correlated with the breeding value f or litter size of the sows. In conclusion, the effects of sperm dose o n fertilization rate and on accessory sperm count in sows were small a nd nonsignificant, indicating only small effects of sperm dose on the functioning of the sperm reservoir in the sow.