Primiparous ewes (n=32) were assigned to dietary treatments in a 2×2 factorial arrangement to determine effects of nutrient restriction and melatonin supplementation on maternal and fetal pancreatic weight, digestive enzyme activity, concentration of insulin-containing clusters and plasma insulin concentrations. Treatments consisted of nutrient intake with 60% (RES) or 100% (ADQ) of requirements and melatonin supplementation at 0 (CON) or 5 mg/day (MEL). Treatments began on day 50 of gestation and continued until day 130. On day 130, blood was collected under general anesthesia from the uterine artery, uterine vein, umbilical artery and umbilical vein for plasma insulin analysis. Ewes were then euthanized and the pancreas removed from the ewe and fetus, trimmed of mesentery and fat, weighed and snap-frozen until enzyme analysis. In addition, samples of pancreatic tissue were fixed in 10% formalin solution for histological examination including quantitative characterization of size and distribution of insulin-containing cell clusters. Nutrient restriction decreased (P⩽0.001) maternal pancreatic mass (g) and α-amylase activity (U/g, kU/pancreas, U/kg BW). Ewes supplemented with melatonin had increased pancreatic mass (P=0.03) and α-amylase content (kU/pancreas and U/kg BW). Melatonin supplementation decreased (P=0.002) maternal pancreatic insulin-positive tissue area (relative to section of tissue), and size of the largest insulin-containing cell cluster (P=0.04). Nutrient restriction decreased pancreatic insulin-positive tissue area (P=0.03) and percent of large (32 001 to 512 000 µm2) and giant (⩾512 001 µm2) insulin-containing cell clusters (P=0.04) in the fetus. Insulin concentrations in plasma from the uterine vein, umbilical artery and umbilical vein were greater (P⩽0.01) in animals receiving 100% requirements. When comparing ewes to fetuses, ewes had a greater percentage of medium insulin-containing cell clusters (2001 to 32 000 µm2) while fetuses had more (P<0.001) pancreatic insulin-positive area (relative to section of tissue) and a greater percent of small, large and giant insulin-containing cell clusters (P⩽0.02). Larger insulin-containing clusters were observed in fetuses (P<0.001) compared with ewes. In summary, the maternal pancreas responded to nutrient restriction by decreasing pancreatic weight and activity of digestive enzymes while melatonin supplementation increased α-amylase content. Nutrient restriction decreased the number of pancreatic insulin-containing clusters in fetuses while melatonin supplementation did not influence insulin concentration. This indicated using melatonin as a therapeutic agent to mitigate reduced pancreatic function in the fetus due to maternal nutrient restriction may not be beneficial.

Reduced food availability in pregnancy influences fetal growth, obstetric outcomes and offspring health in both developing and developed countries. The objective of the present study was to determine responses to moderate global maternal nutrient restriction (MNR) during pregnancy in baboons (Papio hamadryas) – an established non-human primate model for pregnancy-related research. Starting at 30 d gestation (dG), twelve pregnant baboons received 70 % of food (MNR group) consumed by twenty ad libitum-fed pregnant controls. Maternal body weight, BMI, food intake and physical activity were measured before pregnancy, at 90 dG and at 165 dG (full-term 180 dG). Fetal and placental weights were recorded at the time of Caesarean section (90 and 165 dG). Activity patterns were also evaluated in fourteen non-pregnant female baboons. Behavioural observations were made in five non-pregnant, six control and four MNR animals. Pregnant baboons decreased overall physical activity and energy-expensive behaviours compared with non-pregnant baboons. In the MNR group, maternal weight, weight gain and maternal physical activity were reduced compared with the control animals. MNR decreased placental weight and volume compared with control, while fetal weight and length were unaffected. We conclude that decreased physical activity and increased usage of maternal available body stores play an important role in the maternal response to pregnancy. Also, adaptations in maternal behaviour and energy utilisation protect fetal growth during moderate MNR.

Thirty-two crossbred wether lambs (initial live-weight 31 kg) were fed on a diet (metabolizable energy (ME) 12.8 MJ/kg) ad lib. (ADLIB) or restricted to maintain body-weight (MAINT) for a 21 d period. On days 0, 7, 14 and 21, four lambs per treatment were slaughtered, visceral organs weighed and tissues sampled. During the 21 d period, ME intake in ADLIB lambs increased quadratically with an average rate of live-weight gain of 425 g/d. In MAINT lambs, live weight (30 kg) was maintained, and daily ME intake (kJ/kg empty body-weight (EBW)0.75) declined (P < 0.01) quadratically with time. Weights of liver, stomach and small intestines as a percentage of EBW were increased in ADLIB lambs and decreased by 10–33 % in MAINT lambs (treatment × day, P < 0.01). In vitro liver oxygen consumption was not affected by level of feed intake. Estimates of whole-liver O2 consumption (mmol O2/d per kg EBW) increased in ADLIB lambs and were relatively constant in MAINT lambs. These findings suggest that level of feed intake changes the relative proportion of visceral organs to body mass. In addition, the effect of level of feed intake on changes in the relative contribution of visceral organs to whole-body metabolic rate appears to be primarily a result of differences in organ size rather than tissue-specific metabolic activity.