Maternal undernutrition during the pre- and post-conception periods in twin-bearing hairsheep ewes: effects on fetal and placental development at mid-gestation

Placental adaptations supporting fetal growth during normal and adverse gestational environments

NEW FINDINGS

What is the topic of this review? How the placenta, which transports nutrients and oxygen to the fetus, may alter its support of fetal growth developmentally and with adverse gestational conditions. What advances does it highlight? Placental formation and function alter with the needs of the fetus for substrates for growth during normal gestation and when there is enhanced competition for substrates in species with multiple gestations or adverse gestational environments, and this is mediated by imprinted genes, signalling pathways, mitochondria and fetal sexomes.

ABSTRACT

The placenta is vital for mammalian development and a key determinant of life-long health. It is the interface between the mother and fetus and is responsible for transporting the nutrients and oxygen a fetus needs to develop and grow. Alterations in placental formation and function, therefore, have consequences for fetal growth and birthweight, which in turn determine perinatal survival and risk of non-communicable diseases for the offspring in later postnatal life. However, the placenta is not a static organ. As this review summarizes, research from multiple species has demonstrated that placental formation and function alter developmentally to the needs of the fetus for substrates for growth during normal gestation, as well as when there is greater competition for substrates in polytocous species and monotocous species with multiple gestations. The placenta also adapts in response to the gestational environment, integrating information about the ability of the mother to provide nutrients and oxygen with the needs of the fetus in that prevailing environment. In particular, placental structure (e.g. vascularity, surface area, blood flow, diffusion distance) and transport capacity (e.g. nutrient transporter levels and activity) respond to suboptimal gestational environments, namely malnutrition, obesity, hypoxia and maternal ageing. Mechanisms mediating developmentally and environmentally induced homeostatic responses of the placenta that help support normal fetal growth include imprinted genes, signalling pathways, subcellular constituents and fetal sexomes. Identification of these placental strategies may inform the development of therapies for complicated human pregnancies and advance understanding of the pathways underlying poor fetal outcomes and their consequences for health and disease risk.

Effects of Birth Weight on Animal Performance, Fattening Traits and Meat Quality of Lambs

Simple Summary

It is accepted that a low body weight at birth (<4 kg) might impair postnatal muscle and increase adipose tissue development during the whole life of lambs. Therefore, in the present study, we aimed to evaluate the effect of body weight at birth of lambs on the growth performance, ruminal parameters, digestibility, non-carcass components, carcass traits, physicochemical characteristics and fatty acid profile of meat when slaughtered at 27 kg. Compared to the lambs born with a high weight (>5.5 kg), the lambs born with a low body weight showed a worse animal performance during the fattening period, and increased fat depots with a higher content of saturated fatty acids and a reduced tenderness of meat.

Abstract

Intrauterine growth restriction (IUGR) is a key developmental programming factor which might impair both the feed efficiency of lambs and meat quality, since it deeply impacts skeletal muscle and adipose tissue development. To determine the effect of birth weight on the growth performance, ruminal parameters, digestibility, non-carcass components, carcass traits, physicochemical characteristics and fatty acid profile of meat, two experimental groups (six animals in each group) of male Merino lambs with different body weights (BW) at birth (low BW (LW; 3.88 ± 0.281 kg) and high BW (HW; 5.80 ± 0.647 kg)) were used. The lambs were penned with their corresponding ewe during the natural suckling period, being weaned at 15 kg. Then, the lambs were penned individually and offered a complete pelleted diet during the fattening period. All the animals were slaughtered when they reached 27 kg of BW. After weaning, both daily dry matter intake (578 vs. 615 g/day; p = 0.021) and average daily gain (141 vs. 190 g/day; p = 0.004) were significantly lower in LW lambs, and a higher feed:gain ratio was recorded for this group (3.98 vs. 3.45; p = 0.008). Carcass traits did not show differences (p > 0.05) between both groups of lambs, except for higher chilling losses for the LW group (3.29 vs. 2.69%; p = 0.012). Additionally, higher amounts of kidney knob and channel fat were observed for LW lambs (85.4 vs. 152 g; p = 0.028). Apart from a higher hardness of meat in LW lambs (152 vs. 189 Newtons, p = 0.040), no other differences (p > 0.05) were observed in the physicochemical traits of this product; however, the meat of LW lambs tended (p = 0.057) to contain more total fatty acid content with a higher (p = 0.041) proportion of saturated fatty acids than the meat of HW lambs. In conclusion, under the conditions of the present study, a low body weight at birth increased the deposition of fat in carcass and non-carcass components during the fattening period of lambs, thus reducing animal performance and worsening the nutritional indexes of the meat. Accordingly, it seems reasonable to try to identify these animals during early life, to be sold as suckling lambs in the meat market instead of being fattened.

Effect of diet and type of pregnancy on plasma metabolic response in sheep and its further effect on lamb performance

This trial evaluated the individual and interactional effects of diet and type of pregnancy (twin or single) on plasma metabolic response in ewes and their lambs from late pre-partum to late post-partum. Thus, a flock of 18 Ile de France breed sheep, consisting of 8 twin-bearing and 10 single-bearing ewes, were allocated to one of two groups according to their diet, either based on ad libitum naturalized pasture hay (NPH) or red clover hay (RCH), from d 45 pre-partum to d 60 post-partum. Plasma samples were collected at different times to determine albumin, cholesterol, total protein and urea, plus glucose and β-hydroxybutyrate (BHB) concentration in ewes. The data was processed using the lme4 package for R, and SPSS Statistics 23.0 for Windows. The results showed that both diet and type of pregnancy influenced the metabolic profile in ewes, showing an inverse relationship between single- and twin-bearing ewes regarding glucose and especially BHB proportions from pre-partum to birth. During post-partum, higher urea concentrations were observed in twin- and single-bearing ewes fed RCH in contrast to those fed NPH, as a result of the higher-quality forage offered to ewes. Regarding lambs, the diet and type of pregnancy influenced the total protein and urea levels, where an inverse relationship at birth and early post-partum between albumin and cholesterol vs. total protein and urea was detected, reflecting a trend (P value between 0.06 and 0.07) to a better performance by groups of single lambs, especially those from single-bearing ewes fed RCH. Finally, under the conditions of this study, the maternal diet and type of pregnancy influenced the plasma metabolic response in ewes and their lambs, affecting the lamb performance especially at birth.

Evidence for liver energy metabolism programming in offspring subjected to intrauterine undernutrition during midgestation

Background

Maternal undernutrition programs fetal energy homeostasis and increases the risk of metabolic disorders later in life. This study aimed to identify the signs of hepatic metabolic programming in utero and during the juvenile phase after intrauterine undernutrition during midgestation.

Methods

Fifty-three pregnant goats were assigned to the control (100% of the maintenance requirement) or restricted (60% of the maintenance requirement from day 45 to day 100 of midgestation and realimentation thereafter) group to compare hepatic energy metabolism in the fetuses (day 100 of gestation) and kids (postnatal day 90).

Results

Undernutrition increased the glucagon concentration and hepatic hexokinase activity, decreased the body weight, liver weight and hepatic expression of G6PC, G6PD, and PGC1α mRNAs, and tended to decrease the hepatic glycogen content and ACOX1 mRNA level in the dams. Maternal undernutrition decreased the growth hormone (GH) and triglyceride concentrations, tended to decrease the body weight and hepatic hexokinase activity, increased the hepatic PCK1, PCK2 and PRKAA2 mRNAs levels and glucose-6-phosphatase activity, and tended to increase the hepatic PRKAB1 and CPT1α mRNAs levels in the male fetuses. In the restricted female fetuses, the hepatic hexokinase activity and G6PC mRNA level tended to be increased, but PKB1 mRNA expression was decreased and the ACACA, CPT1α, NR1H3 and STK11 mRNA levels tended to be decreased. Maternal undernutrition changed the hepatic metabolic profile and affected the metabolic pathway involved in amino acid, glycerophospholipid, bile acid, purine, and saccharide metabolism in the fetuses, but not the kids. Additionally, maternal undernutrition increased the concentrations of GH and cortisol, elevated the hepatic glucose-6-phosphate dehydrogenase activity, and tended to decrease the hepatic glycogen content in the male kids. No alterations in these variables were observed in the female kids.

Conclusions

Maternal undernutrition affects the metabolic status in a sex- and stage-specific manner by changing the metabolic profile, expression of genes involved in glucose homeostasis and enzyme activities in the liver of the fetuses. The changes in the hormone levels in the male fetuses and kids, but not the female offspring, represent a potential sign of metabolic programming.