Influence of insemination-ovulation interval and sperm cell dose on fertilization in sows.

This experiment was conducted to determine the effects of sperm dose at insemination on fertilization rates and accessory sperm cells attached to day 5 embryos. Multiparous sows (n = 115) were artificially inseminated once with 1 x 10(9), 3 x 10(9) or 6 x 10(9) sperm cells between 3 h and 48 h before ovulation. Transrectal ultrasonography was performed at intervals of 4 h to determine the time of ovulation and sows were killed at 120 +/- 5 h after ovulation to assess the results of fertilization. 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 accessory sperm cells due to the sperm dose was observed. During the insemination-ovulation interval of 12-24 h, the median fertilization rates were 95%, 100% and 100%, and the median accessory sperm counts were 11, 17 and 31 for the 1 x 10(9), 3 x 10(9) and 6 x 10(9) doses, respectively. During the insemination-ovulation interval of 24-36 h, the median fertilization rates were 88%, 95% and 97%, and the median accessory sperm counts were 6, 8 and 11 for the 1 x 10(9), 3 x 10(9) and 6 x 10(9) doses, respectively. No direct relationship was detected between embryo quality and the accessory sperm count but there was a relationship between insemination-ovulation interval and accessory sperm count. The fertilization rate was positively correlated with the breeding value for litter size of the sows. In conclusion, the effects of sperm dose on fertilization rate and on accessory sperm count in sows were small and nonsignificant, indicating only small effects of sperm dose on the functioning of the sperm reservoir in the sow.