Relationship between nutritionally-mediated placental growth restriction and fetal growth, body composition and endocrine status during late gestation in adolescent sheep

The aim was to investigate the consequences of nutritionally-mediated place ntal growth restriction on fetal organ growth, conformation, body compositi on and endocrine status during late gestation. Embryos recovered from super ovulated adult ewes inseminated by a single sire were transferred in single ton to the uterus of peripubertal adolescent recipients. Post-transfer, ado lescent dams were offered a high (H) or moderate (M) level of a complete di et to promote rapid or moderate maternal growth rates, respectively (n = 7 per group). After day 100 of gestation the feed intake of the M darns was a djusted weekly to maintain body condition score. Liveweight gain during the first 100 days of gestation was 301 +/- 24 and 90 +/- 4.6 g/day for the H and M groups, respectively. Maternal plasma concentrations of insulin, IGF- I and urea were significantly higher and non-esterified fatty acid concentr ations significantly lower in H compared with M dams prior to slaughter on day 128 of gestation. At this stage of gestation, total placentome weight w as 50 per cent lower in H compared with hi groups (P < 0.001) and was assoc iated with a 37 per cent reduction in fetal weight (P < 0.01). All variable s of fetal conformation and absolute fetal organ weights, with the exceptio n of the adrenal glands, were lower (P < 0.05) in the fetuses from H intake darns. However, relative fetal organ weights expressed as g/kg fetal body weight, with the exception of the gut, were not influenced by maternal diet ary intake. Furthermore, fetal weight but not maternal nutritional group we re predictive of individual organ weight for all organs dissected. Together these results imply that growth restriction in the fetuses derived from H intake dams was largely symmetrical. Fetal plasma concentrations of insulin , IGF-I and glucose were attenuated (P < 0.05) in fetuses from H compared w ith M groups. The lower fetal body weight in the former group was associate d with a reduction in absolute but not relative crude protein (P < 0.01) an d fat content (P < 0.05). Total fetal liver glycogen content but not concen tration was (P < 0.05) reduced in H versus hi groups. The lower mass of bot h the placenta and fetal liver was due to a reduction in cell number rather than an alteration in cell size. Thus, over-nourishing adolescent sheep is associated with a major restriction in placental growth which mediates a g radual slowing of fetal growth during the final third of pregnancy. (C) 200 0 Harcourt Publishers Ltd.