Embryonic Mortality in the Rabbit is Not Increased After Fertilization by Young Epididymal Spermatozoa

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Abstract
We have examined the claim that rabbit eggs penetrated by epididymal spermatozoa have a higher embryonic mortality than those fertilized by ejaculated spermatozoa. Spermatozoa from the lower corpus epididymidis inseminated into the uterus fertilized 76.5 percent of 204 ova in comparison with 75.9 percent of 199 ova fertilized by ejaculated spermatozoa of the same males inseminated into the contralateral uterine horn. Twenty-seven hours after insemination and HCG injection the 4 cell stage was reached by 11.4 percent of ova fertilized by lower corpus sperm vs. 17.4 percent fertilized by ejaculated sperm. When transferred to contralateral oviducts of synchronized recipients 60.3 percent of 63 ova fertilized by lower corpus sperm implanted and 50.8 percent developed normally to term, compared with 57.1 percent and 47.6 percent respectively for those fertilized by ejaculated spermatozoa. It appears, therefore, that once rabbit epididymal spermatozoa acquire the ability to penetrate the egg, they are equally as competent as ejaculated sperm to support normal embryonic and fetal development.