Clinical, physiological and morphological determinants of the optimal time for insemination of bitches

Bitches have a reproductive cycle that differs from other species in a long luteal phase and pronounced anestrus. Therefore, it is important to study the state of the female reproductive system for effective artificial insemination based on the assessment of the dynamics of gonadotropic and sex hormones, as well as morphological and histological changes during the reproductive cycle. The aim of the study was to develop a method for monitoring the sexual cycle by assessing the dynamics of progesterone after ovulation depending on the number of corpora lutea in bitches. An increase in the number of superficial cells of the vaginal epithelium, which proliferate under the influence of an increase in the content of estradiol-17β, has been established. In this case, parabasal cells die with the formation of intermediate cells, which after apoptosis become spherical cells devoid of nuclei. During the beginning of the estrus, erythrocytes are present in vaginal smears, which disappear by the end of estrus. However, neutrophils appear in vaginal smears 5.2 days after ovulation, which coincides with an increase in the content of progesterone in the blood to 61.86 ± 21.18 ng/ml. A progesterone level of more than 25 ng/ml is a sign of the end of the fertile period and the beginning of the luteal phase during pregnancy or anestrus. The ovulation process lasts 12 hours and is characterized by local proteolima with destruction of the follicle wall, bleeding, formation of a thrombus and corpus luteum. Therefore, 1 full-fledged oocyte is formed from one follicle. The onset of lutealization of follicles was established 1–2 days before ovulation. Prognostic tests of progesterone content, the presence of eosinophils or neutrophils in vaginal smears, the presence of rounded follicles during ultrasound allow determining the ideal time for mating or artificial insemination.