The effects of acute nutrient restriction in the mid-gestational ewe on maternal and fetal nutrient status, the expression of placental growth factors and fetal growth

Abstract

This study explores the hypothesis that acute under-nutrition in mid-gestation reduces maternal and fetal nutrient status and affects the expression of specific regulators of placental growth and function. Welsh Mountain ewes were fed a concentrate diet plus wheat straw to provide 100% of their maintenance requirements. The concentrate ration of nutrient restricted (NR) ewes was reduced from day (d) 83 of gestation and withdrawn from d85 to d90. At d90, half the ewes (NR n=7, control n=8) were euthanased. The remainder (NR n=9, control n=9) were fed their maintenance diet until slaughter at d135. Maternal plasma insulin and IGF-I concentrations decreased during nutrient restriction and NEFA concentrations increased. Fetal IGF-I and insulin concentrations were unaltered by maternal diet. Placental VEGF mRNA expression was reduced at d90 ( P<0.05). IGFBP-3 and IGFBP-2 mRNA expression was reduced at d90 ( P<0.05) and d135 ( P<0.05), respectively. Placental weight was significantly lower in NR ewes at d90 ( P<0.05) and the distribution of placentomes shifted towards the everted phenotype at d135 ( P<0.005). Reduced thoracic girth and uterine fluid volume at d90 ( P<0.05) and decreased fetal lung weight at d90 ( P<0.06) and d135 ( P<0.05) suggest spatial limitation of lung expansion. In summary, acute NR in mid-gestation reduced anabolic drive and mobilised lipid stores in the maternal compartment, whilst fetal nutrient status was maintained. This was accompanied by changes in placental VEGF and IGFBP expression. The growth of the fetal lung appears to have been compromised and this may have adverse consequences for subsequent neonatal respiratory function.