2020 Volume 25 Issue 4 Pages 119-127
Capybara (Hydrochoerus hydrochaeris) is the biggest rodent in the world which lives in South America and well-known at Japanese zoos. Because the placental structure of capybara is similar to human placenta, the use of capybara as an experimental animal is also being considered. It is essential to understand the reproductive physiology of capybara for the planned breeding. However, there are few information about the reproductive physiology of capybara. In the present study, we tried to establish the method of blood sample collection and vaginal smear inspection using husbandary training (no anesthesia and retention). Then, the steroid hormone concentration in plasma and feces was examined to identify the estrous cycle and pregnancy in capybara. Plasma or fecal samples were collected from non-pregnant and pregnant capybaras and steroid hormones were determined by ELISA. In non-pregnant individuals, changes in blood progesterone (P4) and estrone-3-sulfate (E1S) concentrations showed clear estrous cycle-like changes for 3 cycles (average 11.7 ± 0.9 days). Change in blood E1S concentration were consistent with change in fecal estradiol (E2) and appearance of anucleated keratinized epithelial cells in vaginal smear inspection. Fecal E2 concentrations of non-pregnancy capybara also changed like the estrous cycle. In fecal samples of pregnant capybara, the concentration of P4 were higher than that in the non-pregnant capybara. Fecal P4 and E2 concentrations were higher during pregnancy and gradually reduced after parturition. These results suggest that the estrous cycle in capybara may be identified by determining plasma P4, E1S and fecal E2 concentrations and vaginal smear inspection, and pregnancy of capybara can be predicted by measuring the P4 concentration in feces.
