J. Anim Sci.
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J. Anim Sci. 1985. 61:834-843.
© 1985 American Society of Animal Science
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Ovulation Rate and Embryo Survival during Gestation and the Effects of Ovariectomy on Maternal Nurturing Ability1

S. E. Spruill and E. J. Eisen

North Carolina State University2, Raleigh 27695-7621

Abstract

Correlated responses to selection for increased litter size were studied in mice. The selected line (L*) was compared with an unselected control line (K') in two experiments. The first experiment provided a profile of correlated changes in female reproductive traits at d 0, 6, 14 and 18 of gestation. Experiment two examined the effects of ovariectomy on d 18 of gestation, sham surgery and no surgery on litter size and maternal performance. Females of the L+ line had increased (P<.001) body weight, ovulation rate and uterine length at d 0 of gestation compared with K' females, but uterine weight and ovarian weight did not differ. Positive correlated responses (P<.001) in uterine weight and length at d 6 and 14 of gestation were associated with a larger number of viable fetuses. Space per fetus was reduced (P<.001) in the uterus of L+ females, but a lower fetal mortality was still maintained in L+ throughout gestation. Prenatal survival was about 10% higher (P<.06) in L+, the major difference (P<.01) occurring before implantation. A second experiment was conducted to determine the effect of ovariectomy on d 18 on litter size and maternal performance. In experiment two, no significant line x treatment interactions were found for maternal performance, indicating that both lines responded similarly to ovariectomy, line L+ showed a positive correlated response in maternal performance. Ovariectomized females had a reduced (P<.05) number born alive compared with sham-operated females, but the nonsurgically treated females were intermediate. The smaller number born in ovariectomized females leads to an overestimate of cumulative mortality at 18 d of gestation. Pup birth weight was lower (P<.05) in ovariectomized females, perhaps because of a slightly reduced length of gestation. Ovariectomy had no detrimental effect on postnatal maternal performance.

Footnotes

1 Paper No. 9720 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.

2 Dept. of Anim. Sci.






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Copyright © 1985 by the American Society of Animal Science.