The aim of this study was to gain evidence that the FecB and FecXI genes influence ovarian development in foetal life. Foetuses which were homozygous carriers of the Booroola gene (BB), Inverdale gene (II), heterozygous carriers of the Inverdale gene (I+) and non-carriers of both the Booroola (++) and Inverdale genes (++) were recovered at days 40 or 90 of gestation. To eliminate the effects of litter size in the Booroola study, equal numbers of BB and ++ embryos were transferred to recipient ewes. Subsequently no gene-specific differences in litter size were noted at the equivalent of days 40 and 90 of gestation. From these studies the FecB gene was shown to affect body weight, the weight of the mesonephros, and development of germ cells. In essence, at day 40 the mean body weight and mean weight of the mesonephros were lighter in the BB foetuses compared to the ++ animals (P<0.05). Moreover the development of the BB ovaries appeared to be retarded relative to that of the ++ ovaries with respect to mitosis and meiosis of germ cells and also the timing of germ cell atresia. In the Inverdale foetuses, which were recovered after natural matings, differences were observed at the level of the ovary but none were noted with respect to body weight, or weight of mesonephros. At day 40 of gestation the ovaries of the putative II foetuses were significantly lighter (P<0.05) than those of the I+ or control animals. Moreover at day 90 the ++ and putative II ovaries contained significantly fewer (P<0.05) germ cells (i.e. ~110,000) compared to those in the authentic or putative I+ animals (i.e. ~240,000). The differences in either the Booroola or Inverdale foetuses were not accompanied by any significant differences in plasma or pituitary concentrations of follicle-stimulating hormone or plasma inhibin. The results are consistent with the notion that the FecB and FecX genes influence ovarian development in foetal life.

CA, Morris, SA Bisset, RL Baker, TG Watson, DL Johnson, and M Wheeler

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 231-234, 1993
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