Is embryonic mortality increased in normal female rats mated to subfertile males?

Normal female rats were mated to control males or males which were subjected to unilateral testicular heating (43 degrees C for 30 min), irradiation (500 R), efferent duct ligation, arterial ligation or castration; in all males, the contralateral ductus deferens was ligated. All treatments caused reduced fertility and eventually infertility, as judged by the percentage of females becoming pregnant; the infertility was temporary after heating and irradiation. During the periods of reduced fertility, the numbers of fetuses per pregnant female and the fetus/corpus luteum ratios were reduced. In subsequent experiments, after heating of the testis, there was not only failure of fertilization despite the presence of normal numbers of spermatozoa in the uterus, but also an increased rate of embryonic degeneration in normal females. These results provide evidence that the male, while still fertile, can affect the fecundity of the female and the rate of embryo mortality.