Hypoxia and Oxidative Stress Are Associated with Reduced Fetal Growth in Twin and Undernourished Sheep Pregnancies

Abstract

Low birth weight has profound implications for perinatal mortality and morbidity in lambs, causing higher mortality and lower growth potential. Low birth weight, as a consequence of fetal growth restriction, occurs in undernourished and multiple pregnancies, where hypoxia and oxidative stress could play a critical role. Our aim was to establish the effects of nutritional deprivation and pregnancy rank on fetal growth, oxygenation, and oxidative status in sheep pregnancies under extensive Patagonian conditions. At 30 days after mating, single- and twin-bearing ewes were offered only natural pasture (undernutrition group) or natural pasture plus concentrate supplementation (well-nourished group). At day 140 of gestation, blood gases and redox status were evaluated in venous cord blood, and fetal biometric characteristics were obtained after cesarean section. Both maternal undernutrition and twinning led to decreased oxygen supply to the fetuses (p = 0.016 and p = 0.050, respectively), which was associated with decreased intrauterine growth (r = 0.446, p < 0.01). Moreover, twinning increased oxidative stress in cord blood (p < 0.05), which might also contribute to fetal growth restriction. These results reinforce the importance of maternal nutrition, especially for those ewes bearing multiples, and opens new possibilities for nutritional or antioxidant interventions for preventing fetal hypoxia and oxidative stress.

Keywords: fetal growth; nutrition; ovine gestation; oxygen supply; placental–fetal redox.

Figure 1

Live weight (a) and body condition score (BCS) (b) during fetal growth restriction pregnancy in ewes bearing single and twin fetuses, maintained under adequate or deprived nutritional planes. Groups are as follows: SP, pregnant ewes bearing a single fetus, consuming only natural pasture; TP, pregnant ewes bearing twin fetuses, consuming only natural pasture; SP+S, SP ewes consuming natural pasture plus concentrate supplementation; TP+S, TP ewes consuming natural pasture plus concentrate supplementation. Asterisks indicate a significant difference between the supplemented and the non-supplemented groups at the same sampling point; ƒ indicates a significant difference between the supplemented and the non-supplemented groups at the same sampling point, when TP and TP+S are similar; δ indicate a significant difference between the supplemented and the non-supplemented groups at the same sampling point with SP+S also different from TP+S (ANOVA, p < 0.05). A time when the effects of pregnancy rank and nutritional status interaction were evident (p < 0.001) was identified for both traits.

Figure 2

(a) Placental weight per ewe. (b) Plcental weight per fetus. Placental outcome at 140 days of pregnancy in ewes bearing single and twin fetuses, maintained under adequate or deprived nutritional planes. The empty bars correspond to unsupplemented animals. The gray bars correspond to animals fed with natural pasture plus concentrate supplementation. The corresponding effects and their statistical significance are presented as footnote in each figure.

Figure 3

(a) Plasma MDA. (b) Plasma TAC. Antioxidant status of venous cord blood plasma at 140 days of gestation in ewes bearing single and twin fetuses, maintained under adequate or deprived nutritional planes. The mpty bars correspond to unsupplemented animals. The gray bars correspond to animals fed with natural pasture plus concentrate supplementation. The corresponding effects and their statistical significance are presented as footnote in each figure. MDA: malondialdehyde; TAC: total antioxidant capacity.