The effect of the interval from artificial insemination to ovulation on mare fertility rates was studied, taking account the semen deposition site. The intervals were 48 hours and 24 hours prior to ovulation, 48 hours and 72 hours between the two last inseminations. The inseminations in the tip of the uterine horn (GII) were carried out by the deep intravaginal technique using 1/5 of the inseminating dose used in the uterine body (15mL-GI). The mares were teased daily and inseminated on Mondays, Wednesdays and Fridays, starting with a follicle from 3.0 to 3.5 cm of diameter, using fresh semen diluted in skim milk glucose extender. Only one stallion of 20 year-old and well-known fertility was utilized. There was no difference in the conception rates/cycles between the inseminations carried out in the uterine body (42.86%) and in the tip of the uterine horn (45.95%) utilizing average concentrations of 489 and 102 million mobile spermatozoa, respectively. No differences were observed between experimental groups for the same artificial/ovulation interval, but when the conception rates were between intervals in the same semen deposition place, lower conception rates were associated to inseminations carried out before ovulation. However, artificial insemination carried out before and after ovulation, regardless of the artificial insemination/ovulation intervals, resulted in better conception rates. The spermatic concentrations/inseminating dose can be significantly reduced, without damaging fertility, when the semen is placed close to the tubaric papille. However, inseminations are needed before and after ovulation to obtain better fertility rates when using low viability semen in the mare genital tract, in order to establish an adequate sperm reservoir at the time of ovulation.
artificial insemination; conception rate; fresh semen; tip of the uterine horn
