Influence of breed and oestrous cycle on endometrial gland surface density in the mare.

The research analyzed the effect of horse breed and oestrous cycle on the surface density of endometrial glands which can correlate to difference in density of microcotyledons on the placental surface. It was found that Thoroughbred mares have a higher surface density of endometrial glands than Welsh Pony mares, influencing the surface density of placental microcotyledons.

Objective and Methods

• The main objective of the research was to examine the potential variance in the number or density of endometrial glands between the Welsh Pony and Thoroughbred breeds. Also, the study sought to ascertain how the oestrous cycle influences the development and surface density of the endometrial glands.
• The researchers used endometrial biopsies taken from young, fertile Welsh Pony and Thoroughbred mares at specific stages of the oestrous cycle. These biopsies were collected under videoendoscopic visual control from the base of a uterine horn.
• After procuring the biopsies, a computer-assisted morphometric analysis was conducted. This process facilitated the assessment of the surface density of endometrial glands located within the stratum spongiosum.

Results and Conclusions

• The results demonstrated a statistically significant reduction in the endometrial gland surface density in Welsh Pony mares when compared to Thoroughbred mares. This difference was noted during both the oestrus and dioestrus stages of the cycle.
• The research also showed that there is a substantial increase of the epidermal growth factor (EGF) mRNA located in the epithelial cells lining the top portions of endometrial glands. This increase was observed in pregnant mares between the 35th and 40th day after ovulation. This period coincides with the onset of interdigitation among the allantochorion and endometrium to form the microcotyledonary placenta.
• Based on the findings, Thoroughbred mares, having a greater endometrial gland surface density, may have a larger surface density of placental microcotyledons. Hence breed plays an important role in influencing this physiological aspect.