Reproductive and genetic effects of continuous prenatal irradiation in the pig.

The stem germ cells of the prenatal pig are highly vulnerable to the cytotoxic effects of ionizing irradiation. This study was conducted to determine whether sensitivity to killing was also marked by a sensitivity to mutation and how prenatal depletion of the germ-cell population affects reproductive performance. Germ-cell populations were reduced by continuously irradiating sows at dose rates of either 0.25 or 1.0 rad/day for the first 108 days of gestation. The prenatally irradiated boars were tested for sperm-producing ability, sperm abnormalities, dominant lethality, reciprocal translocations, and fertility. Prenatally irradiated females were allowed to bear and nurture one litter, then tested for dominant lethality in a second litter; germ cell survival and follicular development were assessed in their serially sectioned ovaries. Sperm production was not significantly affected in the 0.25-rad boars, but boars irradiated with 1.0 rad per day produced sperm at only 17% of the control level. Incidence of defective sperm was 4.9% and 11.1% in the 0.25 and 1.0 groups, respectively. Four of the 1.0-rad boars were infertile, but prenatal irradiation apparently caused neither dominant lethality nor reciprocal translocations in fertile males. Number of oocytes was reduced to 66 +/- 7% of control in the 0.25-rad gilts, but reproductive performance was unaffected and no dominant lethality was observed. Only 7 +/- 1% of the oocytes survived in the 1.0-rad group. Reproductive performance was normal for the first litter, but four of the 23 sows tested were infertile at the second litter and a significant incidence of dominant lethality was observed.(ABSTRACT TRUNCATED AT 250 WORDS)