Abstract
Mature female mice (ICR-JCL), 8 to 12 weeks of age, were artificially inseminated at 8: 30—9: 30 a.m. on the day of estrus vaginal smear (about 3-7 hr after ovulation) with 3.18×106, 1.83×106 and 1.15×106 sperms from four, two and one cauda epididymidis, respectively, of adult males which were suspended in 50 μl of a modified Krebs-Ringer-bicarbonate solution and incubated at 37°C was under 5% CO2 in air for an hour. Immediately after insemination, pseudopregnancy inducd by an artificial penis and a vaginal tampon. Out of 13 females inseminated with 3.18×106 sperms, 9 females showed placental signs and 8 of them gave birth to the mean 10.5±2.20 (M±S.D.) young at term. Four of 13 females having received 1.83×106 sperms became pregnant giving birth to the mean 4.3±2.1 (M±S.D.) young at term. On the other hand, 5 out of 6 females failed to become pregnant following insemination with 1.15×106 sperms, and only one showed a placental sign and gave birth to twelve young at term. It is concluded that the conception rate and litter size are both dependent on the number of sperms inseminated and that more than 3×106 sperms are necessary to get the conception rate and the litter size comparable to those in natural mating.
