Reproduction and bodyweight of mice after longterm selection for litter size

Components of litter size in mice after 110 generations of selection

“…Selection for larger litter size has led to an increase in female body weight (Joakimsen & Baker 1977, Durrant et al 1980, Fuente et al 1986, van Engelen et al 1995 with some exceptions (Bakker et al, 1978). An increased body weight was also found for the females in the high line in this study.…”

“…The effect of selection for litter size in mice on ovulation rate and embryonic mortality during pregnancy has been reported previously (Joakimsen & Baker 1977, Bakker et al 1978, Durrant et al 1980, Pomp et al 1988, Clutter et al 1994, Ribeiro et al 1996, Johnson et al 1999. These studies revealed that selection for litter size lead to an increase in ovulation rate, and a subsequent reduction in embryonic mortality.…”

“…A negative phenotypic correlation between ovulation rate and prenatal survival has been reported by several authors (reviewed by Blasco et al 1993), but the opposite results have also been published. Joakimsen and Baker (1977), Bakker et al (1978) and Durrant et al (1980) all reported reduced embryo mortality during pregnancy as a result of selection for high litter size. The possibly increased embryonic mortality found in this study raises the question as to whether the increased late pregnancy mortality found in our study is caused by a limited uterus capacity.…”

“…No effect of selection for litter size on fertilisation rate and early embryonic survival could be found is this study. Bakker et al (1978) and Durrant et al (1980) reported a reduction in embryonic mortality at earlier stages of pregnancy, as a result of selection for high litter size. The reason why no, or only a small effect, of selection for litter size on early embryonic mortality could be found in the present study may be because embryonic mortality is not directly affected by limitations in the maternal environment (Knight et al 1977).…”

The effect of restraint stress in early pregnancy in mice

“…Since both hormones show a circadian rhythm in mice and rats (Guillemin, Dear & Liebelt, 1959;Halberg, Peterson & Silber, 1959;Retienne, Zimmermann, Schindler & Lipscomb, 1968) with blood levels peaking before the onset of darkness, it would not be unexpected to see responses to stress varying at different times of the day. Euker & Riegle (1973) (Fowler & Edwards, 1960) or litter size (Falconer, 1960;Elliot, Legates & Ulberg, 1968;Bakker, Wallings & Politiek, 1978) Inadequate progesterone secretion by the CL could account for all the reproductive disturb¬ ances seen in the stressed mice. The proper balance of serum progesterone and oestradiol is necess¬ ary both for embryo transport and development (Roblero & Garavagno, 1979).…”