The index for assessing and predicting fertility in mares

The All-Russian Research Institute for Horse Breeding, 391105, Divovo, Ryazan region, Russia

^* Corresponding author: lebedeva-l18@yandex.ru

Abstract

The evaluation of reproductive qualities of mares is an important element of horse breeding technology. Histological analysis of the endometrium provides information about the mare’s ability to conceive and carry a pregnancy to term. The article presents the results of histological studies of the endometrium in mares of <10 (n=6) and ≥10 (n=13) years old (yо). Two morphometric parameters were used for the analysis: diameter (GDm) and density (GDs) of endometrial glands in diestrus phase of the cycle. There was noted an increase in GDm (20.5 - 62.9 μm, p<0.001) and a decrease in GDs (16.6 - 10.9 units per field of view (ufov), p<0.1) in the endometrium of mares older 10 yo. An endometrial index EI (GDm / GDs, μm/ufov) characterizing the functional state of the endometrium has been proposed. The results of pregnancy rate and the level of life foal birth in mares after histological studies were analyzed. A significant relationship EI with age (p=0.0133) and fertility (p=0.0059) of mares was established. Among mares with EI< 3 µm/ufov only one mare was older than 10 years and all the mares had foaled successfully. The mares with EI>3 µm/fov were older than 10 years and had problems with conception and gestation. In our studies, EI in the range from 3 to 6 µm/ufov could be interpreted as reversible state of the endometrium and after correct treatment it is possible to increase the fertility of mares.