The aim of this study was to determine the effects of maternal undernutrition, applied during physiologically relevant stages of development of the reproductive system, on reproductive development in male sheep fetuses. Groups of ewes (n = 11-19) were fed rations providing either 100% (high; H) or 50% (low; L) of metabolizable energy requirements for live weight maintenance during selected 'windows', bounded by days 0, 30, 50, 65 and 110 after mating. Ewes of control groups (HH (Expts 1 and 2) and HHH (Expt 3)) were fed the H ration from mating until they were killed at day 50 (Expt 1), day 65 (Expt 2) or day 110 (Expt 3) of gestation, whereas ewes of other groups were fed the L ration for the periods days 0-30 of gestation (LH and LHH), days 31-50 or days 31-65 of gestation (HL and HLH), days 65-110 of gestation (HHL), or day 0 to day 50, day 65 or day 110 of gestation (LL and LLL) when the animals were killed. At day 50 of gestation, there was no effect of nutritional treatment on mean fetal mass or fetal testicular mass, but there was increased expression of mRNA for steroidogenic acute regulatory protein (StAR) in the testes of LL animals (P < 0.05) compared with HH controls. Compared with HH animals, the mean plasma testosterone concentrations of LL fetuses tended to be higher, but this result did not reach significance. At day 65 of gestation there were no significant differences between treatments in mean fetal masses, testicular masses, mean plasma testosterone concentrations or StAR mRNA content. At day 110 of gestation, fetal masses in the LLL group were lower (P < 0.01) than those of control fetuses, although no differences in testicular size or fetal plasma testosterone concentrations were recorded. It is concluded that the effects of undernutrition on reproductive development of male sheep fetuses are dependent on the timing of the period of undernutrition.
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