Effects of coitus and the artificial insemination of different volumes of fresh semen on uterine contractions in mares.

This research study explores how sexual intercourse and artificial insemination, using different volumes of fresh semen, can affect uterine contractions in mares. The findings reveal that both sex and the insertion of a large amount of semen increase the total number, amplitude, and duration of uterine contractions, which are believed to assist sperm transport to the fertilization site in the mare’s oviduct.

Methods and Procedures

• The researchers used M-mode ultrasound, a type of imaging technique commonly used to study motion, to record the number, amplitude, and duration of the contractions in both uterine horns and the uterine body of oestrous (in-heat) mares. Measurements were taken four minutes before and four minutes after either sexual intercourse or artificial insemination.
• The artificial insemination involved using either 80.0 ml or 10.0 ml of fresh semen, considerably different volumes to test potential differentiation in the uterine contractions.
• The direction of the uterine contractions in each uterine horn and the uterine body was also measured pre and post coitus.

Results and Findings

• For both coitus and insemination with 80.0 ml of fresh semen, the total number, average amplitude, and average duration of contractions in all parts of the uterus significantly increased.
• In contrast, insemination with a smaller volume of semen (10.0 ml) did not affect the total number or the average duration of contractions in the uterine horns. While the mean amplitude saw a slight increase, this was largely owing to the results from one particular mare.
• The smaller volume insemination also did not affect the contractions in the uterine body, which holds significant importance as it serves as the primary channel for sperm migration.
• The researchers found no considerable difference between the proportion of contractions moving in a cervicotubal (from the cervix to the fallopian tubes) or tubocervical (from the fallopian tubes to the cervix) direction after coitus in any examined part of the uterus.

Implications of the Study

• The findings suggest that larger volumes of semen, whether delivered naturally or artificially, increase uterine activity which could possibly enhance the chances of successful sperm transport to the fertilization site.
• Since insemination with a smaller volume of fresh semen did not have the same effect, it may correspond to a lower likelihood of successful mating, thus having potential implications on the practices of artificial insemination in equine breeding.