Effect of sperm numbers and concentration on sperm transport and uterine inflammatory response in the mare.

The research examines how the concentration of cooled sperm used during insemination impacts sperm transportation and the intensity of resultant uterine inflammation in mares, with results showing a more rapid and intense inflammatory response as sperm concentration increases. However, sperm transport was not significantly affected.

Study Objective and Design

• The purpose of the study was to evaluate the impact of varying sperm concentrations on sperm transport and the severity of the uterine inflammatory response in mares, following insemination.
• The research examined the responses to insemination 2, 4, and 24 hours after the procedure was performed.
• The subjects consisted of 189 estrous mares with a dominant follicle greater than or equal to 35 mm in diameter, with no evidence of bacterial growth or neutrophils in uterine smears.

Detailed Experiment Process

• Each mare was assigned at random to receive one of several intrauterine treatments, namely: insemination with different sperm concentrations (5×10(6) mL(-1), 25×10(6) mL(-1) or 50×10(6) mL(-1)) diluted in 3 mL seminal plasma and 17 mL skim milk; seminal plasma or skim milk extender.
• There was also a control group that did not receive any intrauterine treatment.
• The mares were euthanized either 2, 4, or 24 hours following insemination or infusion, the oviducts were then separated from the uterus, and the uterus and oviducts were flushed with phosphate-buffered saline.
• Post-flushing, an endometrial sample was collected for further histopathological examination. Parameters such as the level of uterine fibrosis and the volume of neutrophils in the stratum compactum were assessed.
• Samples from each tubal and uterine flushing were examined for sperm count and PMN count respectively.

Key Findings

• The results derived from the experiment suggest that the concentration of sperm utilized during insemination instigates a uterine inflammatory response in mares. This response becomes more rapid and intensified as the sperm concentration ascends.
• In contrast to this, the concentration of sperm was not shown to have any substantial influence over sperm transport up to 4 hours following insemination.