Interstrain inseminations and embryo transfers between the SLA miniature pig and standard crossbred pig

The purpose of this study was to determine fertilization and karyotypes of embryos after interstrain insemination and survival of embryos after reciprocal transfers between the National Institutes of Health SLA miniature pig and standard crossbred pig. Recovery of viable embryos indicated fertilization rates were not different in the two strains. Karyotypes of cells from embryos of both strains had the same chromosome number. The wide variation (within animal) in developmental stages of embryos recovered from the SLA minipig suggests the possibility of a prolonged ovulation interval, or a super imposed recruitment of a second set of follicles ovulating a few hours later. Cystic endometrial hyperplasia in the SLA minipig reduced the number of embryos recovered due to mechanical blockage of the uterine horns, thus preventing adequate flushing. SLA minipig recipients with no morphological evidence of cystic endometrial hyperplasia have a similar pregnancy rate to the standard pig. Cystic endometrial hyperplasia may contribute to reduced reproductive efficiency of the SLA minipig as a result of a detrimental effect on early embryo development and/or implantation.