The present study evaluated the effect of nutritional imbalances during pregnancy, either by excess or
deficiency, on fertility and conceptus development in obese-genotype swine (Iberian pig). Twenty-five multiparous sows
were fed, from mating to farrowing, with a standard diet fulfilling either 1.6 folds their daily maintenance requirements
for pregnancy (overfed group, n = 12) or only the 50% of such requirements (underfed group, n = 13). Ten out of 12
overfed but only two out of 13 underfed sows became pregnant (P<0.005). Fetal development was determined in the
pregnant females at Days 35, 50, 75 and 90 of pregnancy. The embryos from undernourished sows were smaller than the
embryos from overfed females as early as at 35 days of pregnancy (P<0.05) and remained smaller until Day 90 of
gestation. However, at the end of pregnancy, there were significant changes in the developmental patterns of fetuses.
Thus, weight and size of the offspring from both nutritional treatments were finally similar at delivery; the same was
found at weaning. There was thereafter a sex-related effect on the growth during the early-postnatal period, with male
piglets of both nutritional origins being significantly heavier and more corpulent at weaning that their sisters (P<0.05). In
conclusion, fetal growth conditioned by malnutrition from periconceptional stages is mainly regulated at the end of the
pregnancy, so that ensure an adequate body-weight and size and, therefore, the survival of the offspring. Afterwards, the
early-postnatal development of the offspring is affected by sex, independently from nutritional origin, with male piglets
growing faster than females.