Effect of hypotaurine on in vitro fertilization and production of term offspring from in vitro-fertilized ova of the Japanese field vole, Microtus montebelli.

The present study was proposed to establish new in vitro fertilization (IVF)-embryo transfer techniques for wild mammals. We demonstrated that IVF of the Japanese field vole, Microtus montebelli, is improved by hypotaurine, and that IVF vole embryos can develop to normal offspring after transfer to recipient females. The rate of IVF was significantly increased when 0.1 or 1 mM of hypotaurine was added during sperm preincubation and fertilization (p < 0.05). Preincubation of spermatozoa with 1 mM hypotaurine prior to oocyte insemination did not have a significant effect on fertilization rate (p < 0.01). At 96 h after insemination, most cultured embryos developed to the 2-cell stage (68-83%), but development to blastocysts was very low (0-3%) for all treatments. Although 43 living offspring were produced after transfer of IVF pronuclear embryos to recipients, the delivery rate of recipients was very low (21%). The litter size of pseudopregnant recipients that produced a litter was 4-11, and the rate of in vivo development of transferred embryos in the pregnant recipients was 41%. These results suggest that hypotaurine affects IVF rather than sperm preincubation and that IVF embryos can develop to normal offspring.