Baggs ewes adapt to maternal undernutrition and maintain conceptus growth by maintaining fetal plasma concentrations of amino acids1

Abstract

Adequate delivery of AA is essential for normal fetal growth and development. Recently, we reported that when ewes from the University of Wyoming flock (farm flock with adequate nutrition) were fed 50% (nutrient-restricted) or 100% (control-fed) of the NRC-recommended nutrient requirements between d 28 and 78 of gestation, fetal weights as well as concentrations of most AA in maternal and fetal blood were substantially reduced in nutrient-restricted vs. control-fed pregnancies. The current study utilized Baggs ewes, which were selected under a markedly different production system (range flock with limited nutrition), to test the hypothesis that adaptation of ewes to nutritional and environmental changes may alter placental efficiency and conceptus nutrient availability in the face of maternal nutrient restriction. Baggs ewes received 50 or 100% of the NRC nutrient requirements between d 28 and 78 of pregnancy. On d 78, maternal uterine arterial and fetal umbilical venous blood samples were obtained, and the ewes were euthanized. Amino acids and their metabolites (ammonia, urea, and polyamines) in plasma were analyzed using enzymatic and HPLC methods. The results showed that maternal plasma concentrations of 9 AA (Asp, Ile, Leu, Lys, Orn, Phe, Thr, Trp, and Val) as well as maternal and fetal plasma concentrations of ammonia and urea were reduced (P < 0.05) in nutrient-restricted compared with control-fed Baggs ewes. However, fetal plasma concentrations of all AA and polyamines did not differ (P = 0.842) between the 2 groups of ewes. Collectively, these findings suggest that Baggs ewes, by adapting to the harsh conditions and limited nutrition under which they were selected, were able to maintain fetal concentrations of AA in the face of a maternal nutrient restriction through augmenting placental efficiency.

Effect of protein or energy restriction during late gestation on hormonal and metabolic status in pregnant goats and postnatal male offspring

“…Because Lys or Met are usually the firstlimiting AA for ruminants (Fenderson and Bergen, 1975), the changes induced by PR or ER may directly influence the growth and development of goats. Moreover, the present study observed unchanged BCAA and Arg concentration among CON and restricted goats, which was in contrast with previous reports in sheep (Kwon et al, 2004;Jobgen et al, 2008). Those studies reported that the concentrations of BCAA and Arg-family AAs were consistently decreased in underfed ewes at early or mid-gestation.…”

“…In addition to GLU (30% to 40%) and acetic acid (5% to 10%), it has been proposed that AA supply a substantial proportion (55%) of the energy demands of fetal growth during late pregnancy in ruminants (Bell et al, 1993). Although maternal AA concentrations appear to be less important than placental transport of AA for fetal growth (Bajoria et al, 2001), these plasma AA concentrations may provide information regarding potential mechanisms responsible for fetal programming in mammals (Kwon et al, 2004;Jobgen et al, 2008;Metzler-Zebeli et al, 2012). In the present study, TAA concentration in plasma from PR goats was increased, whereas that in ER goats was decreased at 125 days of gestation, indicating the pathway of protein and AA metabolism under the condition of low protein supply may be different from that under the condition of low energy supply.…”

“…Reprogramming occurs in fetal tissues and organs to enable the fetus to survive in a restricted uterine environment (Barker, 1999). Much research has been done to understand nutritional manipulation and hormonal and metabolic regulation for fetal growth and development (Jobgen et al, 2008;Yates et al, 2011). Nishina et al (2003) found that plasma cortisol (Cor) was greater in the globally restricted ewes compared with control during the mid-gestation.…”

Maternal obesity: how big an impact does it have on offspring prenatally and during postnatal life?

“…Epigenetics refers to mechanisms that lead to long-term changes in gene expression through chemical modification to or alterations in the packaging of DNA (independent of changes in the DNA sequence) such that the capacity for transcriptional regulation is altered, impacting the fetal phenotype [99]. Typically, epigenetic modifications include DNA methylation, histone modification and RNA interference, mechanisms that are beyond the scope of this review but are further described in a number of excellent review articles [100][101][102][103][104]. Experimentation with animal models, where controlled manipulation of maternal nutrition can be accomplished, has provided solid evidence of dietary manipulation of gene expression [102].…”

Oxygen and Perinatal Origins of Adulthood Diseases

“…4 Human fetuses have several mechanisms to compensate for an acute nutritional restriction, 5 whereas they have limited reserves to compensate for oxygen insufficiencies. Low oxygen levels in the fetoplacental circulation, a condition commonly associated with several obstetric complications such as IUGR and preeclampsia, have been found to impact not only the neonate but also the cardiovascular health of the adult offspring.…”