Vaginal mucus from ewes treated with progestogen sponges affects quality of ram spermatozoa

The use of intravaginal sponges (IS) to synchronize estrous onset in ewes provokes vaginitis, an increase in the vaginal bacterial load, and growth of bacterial species that are not present during spontaneous estrous behavior. The objective of the study was to compare the functional sperm parameters after incubating it with mucus collected from the vagina of ewes during spontaneous estrus or estrous synchronized with IS. Pooled spermatozoa were co-incubated with: (1) vaginal mucus collected from ewes in spontaneous estrus; (2) vaginal mucus collected from ewes in estrus pretreated with progestogen-impregnated IS; (3) synthetic mucus; and (4) medium without mucus as a control group. Sperm samples were evaluated after incubating it for 30 and 90 minutes. The number of colony-forming units (CFUs/mL), pH, and osmolality were greater in the mucus collected from ewes treated with IS than from those untreated (P = 0.046; P < 0.0001, and P < 0.0001, respectively). The percentage of sperm with progressive motility was lower after incubation with vaginal mucus collected from estrous ewes treated with IS than in the other three treatments both, 30 and 90 minutes after incubation (P = 0.0009 and P < 0.0001, respectively). The sample incubated for 30 minutes with mucus from ewes treated with IS had a lower percentage of sperm with intact plasma membrane than all the other treatments (P < 0.0001). The percentage of sperm with functional membrane was significantly lower in the sample incubated for 30 minutes with vaginal mucus from ewes treated with IS than in the other three treatments (P < 0.0001). After 90 minutes, the percentage was still lower than that in the sample collected from ewes during their spontaneous estrus (P = 0.0005). The lowest percentages of sperm with acrosome damage were observed in sperm incubated with mucus collected from sheep in spontaneous estrus for 30 and 90 minutes (P < 0.0001 and P = 0.008, respectively). The percentage of apoptotic spermatozoa was greater in samples incubated during 30 minutes with vaginal mucus collected from ewes treated with IS than in the other three groups (P = 0.0005). The functionality and the viability of ram sperm is negatively affected by the cervical mucus of ewes pretreated with progestagen-impregnated IS used in estrous synchronization treatments. This may partially explain the decrease in conception rate obtained with treatments with IS.