RESUMO
Microtus genus is the herbivorous animal with multiple stomachs, and some of them possess a mating system similar to human and thereby has been expected as a model animal for the large herbivory and human mating system model, respectively. Thus, it is significant to maintain Microtus as an animal genetic resource. We have studied the establishment of assisted reproductive technologies in Alexandromys. montebelli (formerly as Microtus motebelli: A. motebelli), and here, we investigated the effects of hypotaurine treatment to frozen-thawed (FT) spermatozoa and modified timing of nonsurgical artificial insemination (AI) on the number of offspring. As the results, regardless of without or with hypotaurine treatment, when the timing of nonsurgical AI was made closer to the estimated ovulation time (at 7-9 h post coitus), the total number of offspring derived from FT spermatozoa (27 and 28 pups, respectively) increased compared with AI at 4-6 h (five and six pups, respectively) and was equivalent to those of fresh spermatozoa (43 pups) or natural mating (33 pups). These results will lead to further dissemination of nonsurgical AI and could support the "3R principle," which is the standard philosophy of animal experiment because the procedure declines the stress and the recipient can be used repeatedly.