Metabolic profiling of stages of healthy pregnancy in Hu sheep using nuclear magnetic resonance (NMR)

•The important of time-dependent metabolic changes of ewes in pregnancy was proposed.•The gestation stages was an obvious factor affecting the metabolic changes.•Maternal nutritional status is associated with lipid and amino acids metabolism.

Nutrition is one of the most important factors affecting the reproductive performance of animals. Changes in the ovine maternal metabolism during pregnancy are critical to fetal development. To understand the differences in ovine metabolic changes that occur during normal pregnancy, pregnant ewes carrying twin fetuses (n = 8) were selected at 35 days of gestation (dG). All ewes received 100% of National Research Council (NRC) requirements of all nutrients and energy during this experiment. At 50, 70, 90, and 110 dG, maternal plasma samples were collected and designated as one of four corresponding time points (T1, T2, T3, and T4, respectively). Maternal plasma samples were analyzed using 1H nuclear magnetic resonance spectroscopy to compare their metabolomic profiles among time points. We used multivariate pattern recognition to screen for different metabolites in the plasma of the ewes. The body weight and food intake of the ewes were significantly (P < 0.05) different at the four time points, and increased with the passage of pregnancy time. The principal component analysis model results showed that the metabolic states at time points T2 and T3 moved gradually further away from that at T1 and were furthest away from that at T1 at time point T4. Among the different time points, there were thirteen significantly differential metabolites in the maternal plasma (P < 0.05). These metabolites were closely related to amino acid metabolism and lipid metabolism, which might occur at different time points in pregnant ewes. In particular, newly observed changes in 1-methylhistidine and malonate were the first such changes found in maternal plasma. These results demonstrate that the metabolomics approach has value for evaluating metabolism in pregnancy with advancing gestation. In conclusion, during normal pregnancy in Hu sheep, related metabolites play an important role in amino acid and lipid metabolism for meeting the nutritional demands of pregnant ewes.