Abstract
The reproductive physiology of Kiso mares (Equus caballus) and Przewalski mares (Equus przewalskii) was investigated by fecal steroid analyses. Using the Kiso mares as a model, to determine time-dependent changes in the fecal sampling conditions, an enzyme immunoassay method was used to test the level of rectal fecal hormone changes over time (feces were kept at 20 ℃ ). It showed that the fecal progesterone (P4) level in luteal and non-luteal phases began to increase after 8 hours, and the fecal estradiol-17β (E2) and estrone (E1) levels also increased significantly 84 hours later. The P4 pattern of feces was found to be similar in the blood of Kiso mares, with a positive correlation of 0.46 (p<0.01). Based on the profile of fecal P4 in Kiso and Przewalski mares, the average (± SEM) length of the ovarian cycle was 23.6 ± 0.7 and 26.8 ± 0.7 days, respectively. The usual breeding season of Kiso mares is from May or June to November, and that of Przewalski mares is from March or April to the following January, but some mares of the two species exhibited ovarian cycles throughout the year. Fecal P4 levels of both species were increased from the 60-70th days of pregnancy, high values were maintained from 120-300 days, and then they sharply increased just before parturition. E2 and E1 levels also sharply increased from 90 days of pregnancy, reached a peak from 150-190 days, and then gradually decreased approaching parturition. 5α-pregnan-3β-ol-20-one, 5α-pregnane-3, 20-dione, E2 and E1 were mainly detected in feces throughout pregnancy, and such steroid analysis is effective for monitoring pregnancy.
