Parenteral administration of twin-bearing ewes with L-arginine enhances the birth weight and brown fat stores in sheep

Increasing the Understanding of Nutrient Transport Capacity of the Ovine Placentome

Placental nutrient transport capacity influences fetal growth and development; however, it is affected by environmental factors, which are poorly understood. The objective of this study was to understand the impact of the ovine placentome morphological subtype, tissue type, and maternal parenteral supplementation of arginine mono-hydrochloride (Arg) on nutrient transport capacity using a gene expression approach. Placentomal tissues of types A, B, and C morphologic placentome subtypes were derived from 20 twin-bearing ewes, which were infused thrice daily with Arg (n = 9) or saline (Ctrl, n = 11) from 100 to 140 days of gestation. Samples were collected at day 140 of gestation. Expression of 31 genes involved in placental nutrient transport and function was investigated. Differential expression of specific amino acid transporter genes was found in the subtypes, suggesting a potential adaptive response to increase the transport capacity. Placentomal tissues differed in gene expression, highlighting differential transport capacity. Supplementation with Arg was associated with differential expressions of genes involved in amino acid transport and angiogenesis, suggesting a greater nutrient transport capacity. Collectively, these results indicate that the morphological subtype, tissue type, and maternal Arg supplementation can influence placental gene expression, which may be an adaptive response to alter the transport capacity to support fetal growth in sheep.

The regulatory role of eosinophils in adipose tissue depends on autophagy

Introduction

Obesity is a metabolic condition that elevates the risk of all-cause mortality. Brown and beige adipose tissues, known for their thermogenic properties, offer potential therapeutic targets for combating obesity. Recent reports highlight the role of immune cells, including eosinophils, in adipose tissue homeostasis, while the underlying mechanisms are poorly understood.

Methods

To study the role of autophagy in eosinophils in this process, we used a genetic mouse model lacking autophagy-associated protein 5 (Atg5), specifically within the eosinophil lineage (Atg5 eoΔ).

Results

The absence of Atg5 in eosinophils led to increased body weight, impaired glucose metabolism, and alterations in the cellular architecture of adipose tissue. Our findings indicate that Atg5 modulates the functional activity of eosinophils within adipose tissue rather than their abundance. Moreover, RNA-seq analysis revealed upregulation of arginase 2 (Arg2) in Atg5-knockout eosinophils. Increased Arg2 activity was shown to suppress adipocyte beiging. Furthermore, we observed enrichment of the purine pathway in the absence of Atg5 in eosinophils, leading to a pro-inflammatory shift in macrophages and a further reduction in beiging.

Discussion

The data shed light on the importance of autophagy in eosinophils and its impact on adipose tissue homeostasis by suppressing Arg2 expression and limiting inflammation in adipose tissue.

The significance of N-carbamoylglutamate in ruminant production

Improving the efficiency and production of grazing ruminants to support food and fiber production, while reducing the environmental footprint and meeting the welfare needs of the animals, is important for sustainable livestock production systems. Development of new technologies that can improve the efficiency of nitrogen (N) utilization in ruminants, and that are effective and safe, has important implications for ruminant livestock production. N-carbomoylglutamate (NCG) is a functional micronutrient that stimulates endogenous synthesis of arginine, which can improve survival, growth, lactation, reproductive performance, and feed efficiency in mammals. There is a growing body of evidence to support the potential of dietary NCG supplementation to improve the productive capacity and N utilization efficiency of ruminants. This review summarizes the current literature on the effects of dietary supplementation with NCG in ruminants and impacts on production and potential to reduce the environmental footprint of farmed ruminant livestock. The current literature highlights the potential for commercial application in ruminant livestock to improve productivity and N utilization efficiency.

Potential benefits of amino acid supplementation for cervid performance and nutritional ecology, with special focus on lysine and methionine: A review

Deer farming is a thriving industry for venison, velvet antlers, trophy hunting, and other by-products. Feeding and nutrition are important factors for improving production performance, especially dietary protein and amino acids (AAs), as they are the main components of all tissues. Only a few studies on AA supplementation (Lys, Met, Arg) have been performed on cervids, which show positive effects on weight gain, ADG, feed-:gain ratio, plasma AAs, carcass weight, dressing percentage, yield of high-quality muscles, storage of internal fat during winter, DM and CP digestibility, plasma protein- and fat-related metabolite concentrations, antler burr perimeter, weight, length and mineralisation, velvet antler yield, rumen volatile fatty acids, and microbiome composition. All these effects are relevant for supporting the production of cervids products, from venison to velvet or trophy antlers, as well as their general performance and well-being of captive-bred cervids. The current available information suggests that AA supplementation can be especially interesting for animals fed low protein rations, and growing animals, but should be avoided in high rations and during winter, since it may promote the accumulation of internal fat. Potential effects on milk production and the concentrations of different hormones involved in the regulation of the antler cycle should be further explored.

Maternal L-carnitine supplementation promotes brown adipose tissue thermogenesis of newborn goats after cold exposure

Brown adipose tissue (BAT) is an important component of energy expenditure and necessary to maintain body temperature for newborn mammals. In the previous study, we found that L-carnitine was enriched in BAT and promoted BAT adipogenesis and thermogenesis in goat brown adipocytes. However, whether dietary L-carnitine regulates BAT heat production and energy expenditure in lambs remains unclear. In this study, maternal L-carnitine supplementation elevated the rectal temperature, as well as the expression of UCP1 and mitochondrial DNA content to promote BAT thermogenesis in newborn goats. Moreover, maternal L-carnitine supplementation increased the levels of triglycerides (TG), non-esterified fatty acids (NEFA), and lactate in plasma, as well as the content of lipid droplet and glycogen in BAT of newborn goats. Lipidomic analysis showed that maternal L-carnitine supplementation remodeled the lipid composition of BAT in newborn goats. L-carnitine significantly increased the levels of TG and diglyceride (DG) and decreased the levels of glycerophospholipids and sphingolipids in BAT. Further studies showed that L-carnitine promoted TG and glycogen deposition in brown adipocytes through AMPKα. Our results indicate that maternal L-carnitine supplementation promotes BAT development and thermogenesis in newborn goats and provides new evidence for newborn goats to maintain body temperature in response to cold exposure.

Predictive blood biomarkers of sheep pregnancy and litter size

Early detection of sheep pregnancy and the prediction of how many lambs a pregnant ewe delivers affects sheep farmers in a number of ways, most notably with regard to feed management, lambing rate, and sheep/lamb health. The standard practice for direct detection of sheep pregnancy and litter size (PLS) is ultrasonography. However, this approach has a number of limitations. Indirect measurement of PLS using blood biomarkers could offer a simpler, faster and earlier route to PLS detection. Therefore, we undertook a large-scale metabolomics study to identify and validate predictive serum biomarkers of sheep PLS. We conducted a longitudinal experiment that analyzed 131 serum samples over five timepoints (from seven days pre-conception to 70 days post-conception) from six commercial flocks in Alberta and Ontario, Canada. Using LC–MS/MS and NMR, we identified and quantified 107 metabolites in each sample. We also identified three panels of serum metabolite biomarkers that can predict ewe PLS as early as 50 days after breeding. These biomarkers were then validated in separate flocks consisting of 243 animals yielding areas-under-the-receiver-operating-characteristic-curve (AU-ROC) of 0.81–0.93. The identified biomarkers could lead to the development of a simple, low-cost blood test to measure PLS at an early stage of pregnancy, which could help optimize reproductive management on sheep farms.

Effects of dietary supplementation with N-carbamylglutamate on maternal endometrium and fetal development during early pregnancy in Inner Mongolia white cashmere goats

This study investigated the effects of dietary supplementation with N-carbamylglutamate (NCG) on maternal endometrium and fetal development during early pregnancy of Inner Mongolia white cashmere goats. Forty-eight pregnant Inner Mongolia white cashmere goats (average age 3 years old, average lactation parity 2, and average body weight 43.81 ± 2.66 kg) were randomly allocated to three groups: a basal diet (control group, n = 16), a basal diet plus 0.30-g NCG/d (NCG1 group, n = 16), and a basal diet plus 0.40-g NCG/d (NCG2 group, n = 16). All of the does were housed in individual pens and the NCG treatment was conducted from Days 0 to 90 of pregnancy. At Days 17 and 90 of pregnancy, six representative pregnant does in each group were slaughtered. The current study results demonstrated that maternal NCG administration during early pregnancy effectively increased the arginine family of amino acids and the glucogenic amino acids concentrations and promoted the mRNA expression of osteopontin (OPN), αv and β3 integrins, and endometrial development of Inner Mongolia white cashmere goats. The supplementation improved the fetal brown adipose tissue (BAT) stores and the mRNA expression of UCP-1 and BMP7, thereby helping to the fetal early development.

Nutrition and Metabolism: Foundations for Animal Growth, Development, Reproduction, and Health

Consumption of high-quality animal protein plays an important role in improving human nutrition, growth, development, and health. With an exponential growth of the global population, demands for animal-sourced protein are expected to increase by 60% between 2021 and 2050. In addition to the production of food protein and fiber (wool), animals are useful models for biomedical research to prevent and treat human diseases and serve as bioreactors to produce therapeutic proteins. For a high efficiency to transform low-quality feedstuffs and forages into high-quality protein and highly bioavailable essential minerals in diets of humans, farm animals have dietary requirements for energy, amino acids, lipids, carbohydrates, minerals, vitamins, and water in their life cycles. All nutrients interact with each other to influence the growth, development, and health of mammals, birds, fish, and crustaceans, and adequate nutrition is crucial for preventing and treating their metabolic disorders (including metabolic diseases) and infectious diseases. At the organ level, the small intestine is not only the terminal site for nutrient digestion and absorption, but also intimately interacts with a diverse community of intestinal antigens and bacteria to influence gut and whole-body health. Understanding the species and metabolism of intestinal microbes, as well as their interactions with the intestinal immune systems and the host intestinal epithelium can help to mitigate antimicrobial resistance and develop prebiotic and probiotic alternatives to in-feed antibiotics in animal production. As abundant sources of amino acids, bioactive peptides, energy, and highly bioavailable minerals and vitamins, animal by-product feedstuffs are effective for improving the growth, development, health, feed efficiency, and survival of livestock and poultry, as well as companion and aquatic animals. The new knowledge covered in this and related volumes of Adv Exp Med Biol is essential to ensure sufficient provision of animal protein for humans, while helping reduce greenhouse gas emissions, minimize the urinary and fecal excretion of nitrogenous and other wastes to the environment, and sustain animal agriculture (including aquaculture).

L-Arginine Nutrition and Metabolism in Ruminants

L-Arginine (Arg) plays a central role in the nitrogen metabolism (e.g., syntheses of protein, nitric oxide, polyamines, and creatine), blood flow, nutrient utilization, and health of ruminants. This amino acid is produced by ruminal bacteria and is also synthesized from L-glutamine, L-glutamate, and L-proline via the formation of L-citrulline (Cit) in the enterocytes of young and adult ruminants. In pre-weaning ruminants, most of the Cit formed de novo by the enterocytes is used locally for Arg production. In post-weaning ruminants, the small intestine-derived Cit is converted into Arg primarily in the kidneys and, to a lesser extent, in endothelial cells, macrophages, and other cell types. Under normal feeding conditions, Arg synthesis contributes 65% and 68% of total Arg requirements for nonpregnant and late pregnany ewes fed a diet with ~12% crude protein, respectively, whereas creatine production requires 40% and 36% of Arg utilized by nonpregnant and late pregnant ewes, respectively. Arg has not traditionally been considered a limiting nutrient in diets for post-weaning, gestating, or lactating ruminants because it has been assumed that these animals can synthesize sufficient Arg to meet their nutritional and physiological needs. This lack of a full understanding of Arg nutrition and metabolism has contributed to suboptimal efficiencies for milk production, reproductive performance, and growth in ruminants. There is now considerable evidence that dietary supplementation with rumen-protected Arg (e.g., 0.25-0.5% of dietary dry matter) can improve all these production indices without adverse effects on metabolism or health. Because extracellular Cit is not degraded by microbes in the rumen due to the lack of uptake, Cit can be used without any encapsulation as an effective dietary source for the synthesis of Arg in ruminants, including dairy and beef cows, as well as sheep and goats. Thus, an adequate amount of supplemental rumen-protected Arg or unencapsulated Cit is necessary to support maximum survival, growth, lactation, reproductive performance, and feed efficiency, as well as optimum health and well-being in all ruminants.

Dietary rumen-protected L-arginine or N-carbamylglutamate attenuated fetal hepatic inflammation in undernourished ewes suffering from intrauterine growth restriction

This study aimed to explore whether dietary rumen-protected L-arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation to feed-restricted pregnant ewes counteracts fetal hepatic inflammation and innate immune dysfunction associated with intrauterine growth retardation (IUGR) in ovine fetuses. On d 35 of pregnancy, twin-bearing Hu ewes (n = 32) were randomly assigned to 4 treatment groups (8 ewes and 16 fetuses per group) and fed diets containing 100% of the NRC requirements (CON), 50% of the NRC requirements (RES), RES + RP-Arg (20 g/d) (RESA), or RES + NCG (5 g/d) (RESN). At 08:00 on d 110 of gestation, fetal blood and liver tissue samples were collected. The levels of triglyceride, free fatty acid, cholesterol and β-hydroxybutyrate in the fetal blood of RESA and RESN groups were lower (P < 0.05) than those of the RES group, but were higher (P < 0.05) than those of the CON group. The interleukin (IL)-6 and IL-1 levels in fetal blood and liver tissue as well as the myeloid differentiation primary response 88 (MyD88), transforming growth factor β (TGFβ), and nuclear factor kappa B (NF-κB) mRNA levels in the fetal liver were decreased (P < 0.05) by the NCG or RP-Arg supplementation compared to the RES treatment. Similarly, the toll-like receptor (TLR)-4, MyD88, TGFβ, and p-c-Jun N-terminal kinase (JNK) protein levels in the fetal liver were reduced (P < 0.05) in the NCG and RP-Arg -supplemented groups compared to the RES group. These results showed that dietary supplementation of RP-Arg or NCG to underfed pregnant ewes could protect against IUGR fetal hepatic inflammation via improving lipid metabolism, down-regulating the TLR-4 and the inflammatory JNK and NF-κB signaling pathways, and decreasing cytokine production in ovine fetal blood and liver tissue.

Effects of maternal nutrition and rumen-protected arginine supplementation on maternal carotid artery hemodynamics and circulating amino acids of ewes and offspring

Multiparous Rambouillet ewes (n = 32) were allocated in a completely randomized design to determine if rumen-protected L-arginine (RP-Arg) supplementation during mid- and late gestation would 1) alter maternal carotid artery hemodynamics and 2) affect circulating amino acids associated with arginine metabolism in dams from day 54 of gestation to parturition and in their offspring from birth to 54 d of age. Ewes were assigned to one of three treatments from day 54 ± 3.9 to parturition: control (CON; 100% nutrient requirements), restricted (RES; 60% of CON), and RES plus 180 mg RP-Arg•kg BW-1•d1 (RES-ARG). Ewes were penned individually in a temperature-controlled facility. Carotid artery hemodynamics was measured via Doppler ultrasound at day 50 and 130 of gestation. Maternal serum was collected at day 54 and 138 of gestation and at parturition. At parturition, lambs were immediately removed from their dams and reared independently. Lamb serum samples were collected at birth and 1, 3, 7, 33, and 54 d of age. Pulsatility index was the only hemodynamic measurement altered by dietary treatment, where day 130 measurements were greater (P ≤ 0.04) for RES and RES-ARG compared with CON. The change in pulsatility index was greater (P < 0.01) for RES compared with CON but tended to be intermediate (P ≥ 0.12) for RES-ARG. Maternal serum Arg, Cit, and Asp at day 138 were greater (P < 0.01) for CON compared with RES and RES-ARG; serum Orn at day 138 was greater (P = 0.04) for CON compared with RES. Maternal serum Cit at parturition was greater (P ≤ 0.03) for CON and RES-ARG compared with RES. Offspring serum Arg was affected by a maternal treatment by day of age interaction (P = 0.03), where at day 3, CON and RES-ARG had greater (P ≤ 0.03) serum Arg concentrations than RES, and at day 54, RES-ARG was greater than (P = 0.002) CON and RES was intermediate and did not differ from (P ≥ 0.09) CON and RES-ARG. Offspring serum Orn and Cit were less (P ≤ 0.03) for RES and RES-ARG compared with CON. Results indicate that distal tissue blood perfusion decreased due to maternal RES, and RES-ARG was able to improve perfusion but not to the level of CON ewes. Further, maternal RP-Arg altered offspring Arg and related amino acid concentrations during the postnatal period.

Melatonin Regulates Differentiation of Sheep Brown Adipocyte Precursor Cells Via AMP-Activated Protein Kinase

In sheep industry, hypothermia caused by insufficient brown adipose tissue (BAT) deposits is one of the major causes of lamb deaths. Enhancing the formation and function of BAT in neonatal lamb increases thermogenesis and hence reduces economic losses. The aim of the present study was to explore the effect and mechanism of melatonin on sheep brown adipocyte formation and function. Sheep brown adipocyte precursor cells (SBACs) isolated from perirenal BAT were treated with melatonin (1 and 10 nM). The SBACs subjected to melatonin exhibited a decreased proliferation ability, accompanied by down-regulated proliferating cell nuclear antigen, cyclin D1, and CDK4 protein contents in a melatonin dose-dependent manner. Melatonin promoted brown adipocyte formation and induced the expression of brown adipogenic markers, including uncoupling protein 1 and PR domain-containing 16 during differentiation of SBAC. Moreover, the AMP-activated protein kinase α1 (AMPKα1) activity was positively correlated with brown adipocyte formation potential. Importantly, melatonin effectively activated AMPKα1. Furthermore, promotional effects of melatonin were abolished by AMPKα1 knockout, suggesting the involvement of AMPKα1 in this process. Collectively, these results suggested that melatonin enhanced brown adipocyte formation in SBACs in vitro through activation of AMPKα1.

Amino Acid Nutrition and Reproductive Performance in Ruminants

Amino acids (AAs) are essential for the survival, growth and development of ruminant conceptuses. Most of the dietary AAs (including L-arginine, L-lysine, L-methionine and L-glutamine) are extensively catabolized by the ruminal microbes of ruminants to synthesize AAs and microbial proteins (the major source of AAs utilized by cells in ruminant species) in the presence of sufficient carbohydrates (mainly cellulose and hemicellulose), nitrogen, and sulfur. Results of recent studies indicate that the ruminal microbes of adult steers and sheep do not degrade extracellular L-citrulline and have a limited ability to metabolize extracellular L-glutamate due to little or no uptake by the cells. Although traditional research in ruminant protein nutrition has focused on AAs (e.g., lysine and methionine for lactating cows) that are not synthesized by eukaryotic cells, there is growing interest in the nutritional and physiological roles of AAs (e.g., L-arginine, L-citrulline, L-glutamine and L-glutamate) in gestating ruminants (e.g., cattle, sheep and goats) and lactating dairy cows. Results of recent studies show that intravenous administration of L-arginine to underfed, overweight or prolific ewes enhances fetal growth, the development of brown fat in fetuses, and the survival of neonatal lambs. Likewise, dietary supplementation with either rumen-protected L-arginine or unprotected L-citrulline to gestating sheep or beef cattle improved embryonic survival. Because dietary L-citrulline and L-glutamate are not degraded by ruminal microbes, addition of these two amino acids may be a new useful, cost-effective method for improving the reproductive efficiency of ruminants.

Amino Acids in the Nutrition and Production of Sheep and Goats

In sheep and goats, amino acid nutrition is essential for the maintenance of health and productivity. In this review, we analysed literature, mostly from the past two decades, focusing on assessment of amino acid requirements, especially on the balance of amino acid profiles between ruminal microbial protein and animal production protein (foetal growth, body weight gain, milk and wool). Our aim was to identify amino acids that might limit genetic potential for production. We propose that much attention should be paid to amino acid nutrition of individuals with greater abilities to produce meat, milk or wool, or to nourish large litters. Moreover, research is warranted to identify interactions among amino acids, particularly these amino acids that can send positive and negative signals at the same time.

Rumen-protected arginine in ewe lambs: effects on circulating serum amino acids and carotid artery hemodynamics

Sixty nonpregnant, nulliparous Rambouillet ewes (51 ± 1.4 kg initial body weight) were used in a completely randomized design to determine 1) if rumen-protected l-Arg (RP-ARG) supplementation would increase serum concentrations of amino acids resulting from Arg supplementation and metabolism, and decrease serum concentrations of amino acids that compete with Arg for transporters, 2) if RP-ARG supplementation would alter carotid artery hemodynamics, and 3) the most effective oral dose of RP-ARG to positively increase both circulating amino acids and improve peripheral tissue blood perfusion as measured by carotid hemodynamics. Ewes were penned individually in a temperature-controlled facility. Ewes were randomly assigned to one of four treatments: a control group that received no supplemental Arg (CON; 50 g of finely ground corn, only), or Arg-supplemented groups that received 90 (90), 180 (180), or 360 (360) mg RP-ARG·kg BW-1·d-1 mixed in 50 g of finely ground corn. Supplements were administered once daily for 14 d and fully consumed before the delivery of a total pelleted diet at 0630 and 1830 hours daily. Baseline and final blood samples were collected at days 0 (before treatment initiation) and 15, respectively. Doppler ultrasound was used to assess carotid arterial hemodynamics at 0600 hours on days 0 (before treatment initiation), 5, 8, 12, and 15. After 14 d of supplementation, ewes fed 180 had greater Arg (P = 0.05) and Orn (P = 0.05) and tended (P = 0.08) to have greater Asp in serum than ewes fed 90, and for these amino acids, ewes fed 180 were similar (P ≥ 0.16) compared with ewes fed 360. All supplemented ewes (90, 180, and 360) had a negative change (P = 0.02) from baseline when normalized to CON for the pulsatility and resistance indices, which indicate greater distal tissue blood perfusion and lower vascular resistance of blood flow, respectively. Additionally, there were quadratic responses for the pulsatility and resistance indices (P = 0.03 and 0.01, respectively) where ewes fed 180 had the greatest change from baseline when normalized to CON. Results indicate that Arg supplementation increased serum amino acid concentrations and improved peripheral tissue blood perfusion. The 180 mg·kg BW-1·d-1 RP-ARG dose was determined to be the optimal dose for nonpregnant, nulliparous Rambouillet ewes.

Dietary rumen-protected arginine and N-carbamylglutamate supplementation enhances fetal growth in underfed ewes

The present study was conducted with an ovine intrauterine growth restriction (IUGR) model to test the hypothesis that dietary rumen-protected l-arginine (RP-Arg) or N-carbamylglutamate (NCG) supplementation in underfed ewes is effective in enhancing fetal growth. Between Days 35 and 110 of pregnancy, 32 multiparous ewes carrying two fetuses were randomly assigned to one of four groups: a control (CG) group (n=8; 100% National Research Council (NRC) requirements for pregnant sheep), a nutrient-restricted (RG) group (n=8; fed 50% NRC requirements, and two treatment (ARG and NCG) groups (n=8 in each group; fed 50% NRC requirements supplemented with 20gday-1 RP-Arg or 5gday-1 NCG. All ewes were killed on Day 110 of pregnancy to determine fetal weight and fetal organ weights, and metabolites and hormones in fetal plasma, amino acid concentrations in the fetal liver and longissimus dorsi muscle, and expression of mRNAs in the somatotropic axis. Maternal and fetal bodyweight and the weight of most fetal organs expressed as a percentage of bodyweight increased in response to ARG and NCG compared with values for fetuses from RG ewes. Fetal plasma concentrations of insulin, insulin-like growth factor 1, total amino acids, lactate, thyroxine, and the thyroxine/tri-iodothyronine ratio were lower in fetuses from RG ewes compared with the other treatment groups, but concentrations of growth hormone, non-esterified fatty acids, and total cholesterol were greater in fetuses from RG ewes. Maternal RP-Arg or NCG supplementation increased concentrations of amino acids in fetal tissues and expression of mRNAs for somatotropic axis proteins in fetuses from RG ewes. These findings suggest that maternal RP-Arg and NCG supplementation of underfed ewes decreases fetal IUGR by improving metabolic homeostasis of fetal endocrinology, increasing the availability of amino acids in the fetal liver and longissimus dorsi muscle and affecting the expression of somatotropic axis genes.

Effects of l-arginine on endometrial estrogen receptor α/β and progesterone receptor expression in nutrient-restricted sheep

This study aimed to determine the effects of l-arginine (L-Arg) supplementation on steroid hormone receptors in non-pregnant ovine endometrium. All experimental ewes were randomly assigned to either a control group (n = 6), a nutrient-restricted group (n = 6), or an L-Arg supplemented nutrient-restricted group (n = 6). The effects of L-Arg on estrogen receptor α/β (ERα/β) and progesterone receptor (PGR) expression in the ovine endometrium were assessed. Our results showed that levels of ERβ and PGR expression were significantly increased by nutrient restriction, but L-Arg counteracted the effect of nutrient restriction on ERβ and PGR expression (p < 0.05). Also, expression of endometrial ERα was substantially increased (p < 0.05) by L-Arg supplementation. Furthermore, ERα/β and PGR were mainly detected in the endometrial luminal epithelium and glandular epithelium. Therefore, we isolated and identified endometrial epithelial cells (EECs) from sheep. Different concentrations of L-Arg were added to investigate the effects on ERα/β and PGR in EECs. The expression levels of endothelial nitric oxide synthase, ERβ, and PGR were significantly increased in response to low-concentration (200 μmol) L-Arg supplementation, which subsequently decreased with a high concentration (800 μmol) (p < 0.05). Otherwise, ERα expression was remarkably increased at both L-Arg concentrations in EECs (p < 0.05). Overall, the results indicated that L-Arg performed crucial roles in the regulation of ovine steroid hormone receptor expression in the endometrium. The results of this study provide a theoretical basis and technical means for the normal function of endometrium in response to low nutrient levels.

Identification of the association between FABP4 gene polymorphisms and milk production traits in Sfakia sheep

The aim of this study was to estimate the effect of variation in the fatty acid binding protein 4 gene (FABP4) on milk production traits in Greek Sfakia sheep. Polymerase chain reaction – single-stranded conformational polymorphism (PCR-SSCP) analysis was used to genotype a total of 374 Sfakia ewes for two regions of FABP4 located around exon 2–intron 2 (Region 1) and exon 3–intron 3 (Region 2). Each month, for a period of 6 months, milk samples were collected from the ewes to measure total milk yield, fat content, protein content, lactose content, non-fat solid content, pH, and somatic cell count (SCC). A general linear model was used to test the association between the variation observed in FABP4 and milk production traits. Four gene variants (A1–A4) were found in Region 1 and two variants (C1–C2) were found in Region 2. In the first region, the FABP4 genotype significantly affected (P<0.05) non-fat solid levels, fat content, and SCC. The presence of the A2 variant was significantly associated (P<0.05) with decreased SCC, while the presence of A4 was significantly associated with decreased milk yield (P<0.01), increased non-fat solid content (P<0.05), decreased fat content (P<0.01), increased lactose content (P<0.05), and increased pH (P<0.05). In the second region, FABP4 genotype had an effect (P<0.05) on protein content and the presence of the C2 variant was associated (P<0.05) with increased protein content, decreased SCC, and lower pH. The results suggest an association between variation in ovine FABP4 and milk production traits in Greek Sfakia sheep. Nevertheless, further analyses in independent sheep populations of increased size will strengthen these findings.

Consequences of twinning induction to Noemi ewes by a recombinant human follicle-stimulating hormone compared with pituitary-derived porcine follicle-stimulating hormone on follicular dynamics, maternal biochemical attributes, and neonatal traits

AIM

The aim of this study was to investigate the effectiveness of using recombinant human follicle-stimulating hormone (FSH) compared with pituitary-derived porcine FSH given as one dose or multiple doses on the neonatal traits, follicular dynamics, and maternal blood biochemical constituents in Noemi ewes.

MATERIALS AND METHODS

A 3×2 factorial arrangement was designed utilizing 60 adults Noemi ewes to test the effects of using two sources of FSH (human vs. porcine) in addition to control, either given as a single total dose or six descending doses to provoke twinning. Six treatments (T) were tested (n=10 ewes/T). C1 and C6 served as control ewes given saline as one dose and six doses, respectively; H1 and H6 ewes were given human FSH as one and six doses; and P1 and P6 ewes were given porcine FSH similar to the above treatments. Saline and/or FSH administration were administered at days 8, 9, and 10 of the 10-day controlled internal drug release (CIDR) implant. At CIDR removal, fertile rams were used for natural mating. Blood samples for the assessment of serum metabolites were collected.

RESULTS

Twinning increased in FSH-treated ewes than control. However, giving FSH of either source as a single dose resulted in a higher incidence of stillbirths. Pregnancy rates were 30, 40, 50, 60, 70, and 80% in C1, C6, P1, P6, H1, and H6, respectively. Respective percent of ewes delivering twins/multiple birth was 0, 0, 80, 66.7, 71.4, and 87.5%. FSH of human source was more efficient for folliculogenesis than porcine FSH. Administration of FSH increased blood cholesterol, decreased high-density lipoprotein; however, low-density lipoprotein levels were not different than control. Moreover, an interaction (p<0.05) exists between source and type of FSH administration on blood glucose. Six doses of FSH elevated blood protein. Blood albumin decreased by porcine-FSH but not affected by human-FSH. Blood globulins were not different due to source of FSH, whereas giving FSH as six doses increased globulins than in single-dose protocol. Contrariwise, an interaction was found between source and type of FSH administration on elevating the activity of alanine aminotransferase and reducing the activity of aspartate aminotransferase.

CONCLUSION

Administration of human FSH at 180 IU in six descending doses resulted in the best neonatal outcomes and maternal health in Noemi ewes.

Parenteral administration of l-arginine to twin-bearing Romney ewes during late pregnancy is associated with reduced milk somatic cell count during early lactation

Maternal milk is the primary source of nutrition for suckling mammals, and its yield and composition are important determinants of survival during the early neonatal period. The objective of this study was to examine whether parenteral administration of l-Arg to twin-bearing ewes, during mid to late pregnancy, influenced prepartum maternal mammary gland development and subsequent lactation performance in the early postpartum period (14 d). At 80 d of pregnancy, multiparous Romney ewes were housed indoors in group pens, split into 2 cohorts, and fed a lucerne-based pellet diet, formulated to meet 100% of National Research Council-recommended requirements for twin-bearing pregnant ewes, once a day. Cohort 1 was administered l-Arg (72.7 mg/kg of live weight via i.v, 3 times a day) from d 100 of pregnancy until d 140. At d 140, ewes were euthanized and maternal mammary tissues were collected for analysis of the biochemical indices total DNA, RNA, protein, protein synthetic efficiency (protein:RNA), cell size (protein:DNA), transcriptional efficiency (RNA:DNA), and the abundance of mammalian target of rapamycin (mTOR) and mTOR^Ser2448 protein. Cohort 2 was administered an identical l-Arg regimen as cohort 1, but from d 100 until parturition. Milk was collected over a 14-d period (d 1, 4, 7, 10, and 14) to assess milk yield and composition. In cohort 1, total mammary DNA (cell number) tended to be higher in l-Arg ewes, with no change in total mammary RNA or protein content, biochemical indices of protein synthetic efficiency, cell size or transcriptional efficiency, or mTOR protein abundance or phosphorylation. In cohort 2, milk composition analysis from l-Arg ewes showed lower (d 7-14) milk somatic cell counts, greater crude protein percentage from d 7 to 10 but lower at d 14, and altered absolute concentrations of some free AA (d 7 and 14) compared with controls. We propose that parenteral administration of l-Arg during late pregnancy is associated with increased mammary gland cellular content and decreased somatic cell counts during early lactation.

Intravenous maternal -arginine administration to twin-bearing ewes, during late pregnancy, is associated with increased fetal muscle mTOR abundance and postnatal growth in twin female lambs

The aims of this study were to determine whether parenteral Arg administered to well-fed twin-bearing ewes from 100 to 140 d of pregnancy influences fetal skeletal muscle growth, the abundance and activation of mechanistic target of rapamycin (mTOR) protein, and postnatal muscle growth of the offspring. Ewes fed 100% of NRC-recommended nutrient requirements for twin-bearing ewes were administered an intravenous bolus of either 345 μmol Arg HCl/kg BW or saline solution (Control) 3 times per day. At 140 d of pregnancy (P140), a group of 11 Control and 9 Arg-treated ewes were euthanized and hind leg muscles and longissimus dorsi (LD) were excised and weighed. A sample of LD was snap frozen in liquid nitrogen for later analysis of free AA (FAA) concentration, mTOR abundance and phosphorylation, and biochemical indices (DNA, RNA, and protein content). For the remaining 25 ewes (Arg, = 13, and Control, = 12), Arg administration was continued until the initiation of parturition and ewes were allowed to lamb. Lambs were weaned at postnatal Day 82 and grazed on pasture until postnatal day 153 (PN153), when a subset of 20 lambs ( = 10 per group) was euthanized. At P140, only the psoas major was heavier in the Arg-administered group compared with the Control group. Female lambs from ewes supplemented with Arg (Arg-F) had increased abundance of total mTOR, RNA concentration, and RNA:DNA ratio in LD compared with female lambs from Control ewes (Con-F), whereas males did not differ. At PN153, Arg-F were heavier than Con-F and had heavier LD and plantaris and a trend for heavier psoas major muscles compared with Con-F. In contrast, BW and individual muscle weights did not differ in male lambs. Lambs from Arg-treated ewes had heavier semimembranosus and tended to have heavier biceps femoris compared with Control lambs. The RNA concentration in LD was greater in Arg-F compared with Con-F, and DNA concentration was greater in the Arg group compared with the Control group. In conclusion, Arg administration to the ewe during gestation increases female lamb weight and muscle weight after birth and these changes are associated with altered mTOR protein abundance and have potential implications for sheep production.

Dietary -carbamylglutamate and rumen-protected -arginine supplementation ameliorate fetal growth restriction in undernourished ewes

This study was conducted with an ovine intrauterine growth restriction (IUGR) model to test the hypothesis that dietary -carbamylglutamate (NCG) and rumen-protected -Arg (RP-Arg) supplementation are effective in ameliorating fetal growth restriction in undernourished ewes. Beginning on d 35 of gestation, ewes were fed a diet providing 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations (50% NRC), 50% of NRC recommendations supplemented with 20 g/d RP-Arg (providing 10 g/d of Arg), and 50% of NRC recommendations supplemented with 5 g/d NCG product (providing 2.5 g/d of NCG). On d 110, maternal, fetal, and placental tissues and fluids were collected and weighed. Ewe weights were lower ( < 0.05) in nutrient-restricted ewes compared with adequately fed ewes. Maternal RP-Arg or NCG supplementation did not alter ( = 0.26) maternal BW in nutrient-restricted ewes. Weights of most fetal organs were increased ( < 0.05) in RP-Arg-treated and NCG-treated underfed ewes compared with 50% NRC-fed ewes. Supplementation of RP-Arg or NCG reduced ( < 0.05) concentrations of β-hydroxybutyrate, triglycerides, and ammonia in serum of underfed ewes but had no effect on concentrations of lactate and GH. Maternal RP-Arg or NCG supplementation markedly improved ( < 0.05) concentrations of AA (particularly arginine-family AA and branched-chain AA) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids within nutrient-restricted ewes. These novel results indicate that dietary NCG and RP-Arg supplementation to underfed ewes ameliorated fetal growth restriction, at least in part, by increasing the availability of AA in the conceptus and provide support for its clinical use to ameliorate IUGR in humans and sheep industry production.

L-Arginine promotes protein synthesis and cell growth in brown adipocyte precursor cells via the mTOR signal pathway

L-Arginine has been reported to enhance brown adipose tissue developments in fetal lambs of obese ewes, but the underlying mechanism is unknown. The present study tested the hypothesis that L-arginine stimulates growth and development of brown adipocyte precursor cells (BAPCs) through activation of mammalian target of rapamycin cell signaling. BAPCs isolated from fetal lambs at day 90 of gestation were incubated   for 6 h in arginine-free DMEM, and then cultured in DMEM with concentrations of 50, 100, 200, 500 or 1000 μmol L-arginine/L for 24-96 h. Cell proliferation, protein turnover, the mammalian target of rapamycin (mTOR) signaling pathway and pre-adipocyte differentiation markers were determined. L-arginine treatment enhanced (P < 0.05) BAPC growth and protein synthesis, while inhibiting proteolysis in a dose-dependent manner. Compared with 50 and 100 μmol/L (the concentrations of arginine in the maternal plasma of obese ewes), 200 μmol L-arginine/L (the concentrations of arginine in the maternal plasma of obese ewes receiving arginine supplementation) increased (P < 0.05) the abundances of phosphorylated mTOR, P70^S6K and 4EBP1, as well as the abundances of PGC1α, UCP1, BMP7 and PRDM16. These novel findings indicate that increasing extra-cellular arginine concentration from 50 to 200 µmol/L activates mTOR cell signaling in BAPCs and enhances their growth and development in a dose-dependent manner. Our results provide a mechanism for arginine supplementation to enhance the development of brown adipose tissue in fetal lambs.

Invited review: impact of specific nutrient interventions during mid-to-late gestation on physiological traits important for survival of multiple-born lambs

To improve production efficiency, the sheep meat industry has increased flock prolificacy. However, multiple-born lambs have lower birth weights, increased mortality and reduced growth rate compared with single-born lambs. Lamb mortality is a major issue for livestock farming globally and solutions are required to increase survival to realise the value of increased flock fecundity. Nutrition during gestation can influence maternal-foetal placental nutrient transfer and thus foetal growth and organ/tissue development, as well as improve postnatal productivity. This review covers the challenges and opportunities associated with increased prolificacy, highlights gaps in our knowledge and identifies some opportunities for how targeted intervention with specific nutrients during mid-to-late pregnancy may influence lamb survival and productivity with a specific focus on pasture-based systems. This time frame was selected as intervention strategies in short-time windows post-pregnancy scanning and before lambing to improve lamb survival in high-risk groups (e.g. triplets) are likely to be the most practical and economically feasible options for pasture-based extensive farming systems.

Net mineral requirements of dairy goats during pregnancy

Mineral requirements of pregnant dairy goats are still not well defined; therefore, we investigated the net Ca, P, Mg, Na and K requirements for pregnancy and for maintenance during pregnancy in two separate experiments. Experiment 1 was performed to estimate the net Ca, P, Mg, Na and K requirements in goats carrying single or twin fetuses from 50 to 140 days of pregnancy (DOP). The net mineral requirements for pregnancy were determined by measuring mineral deposition in gravid uterus and mammary gland after comparative slaughter. In total, 57 dairy goats of two breeds (Oberhasli or Saanen), in their third or fourth parturition, were randomly assigned to groups based on litter size (single or twin) and day of slaughter (50, 80, 110 and 140 DOP) in a fully factorial design. Net mineral accretion for pregnancy did not differ by goat breed. The total daily Ca, P, Mg, Na and K requirements for pregnancy were greatest in goats carrying twins (P<0.05), and the requirements increased as pregnancy progressed. Experiment 2 was performed to estimate net Ca, P, Mg, Na and K requirements for dairy goat maintenance during pregnancy. In total, 58 dairy goats (Oberhasli and Saanen) carrying twin fetuses were assigned to groups based on slaughter day (80, 110 and 140 DOP) and feed restriction (ad libitum, 20% and 40% feed restriction) in a randomized block design. The net Ca, P and Mg requirements for maintenance did not vary by breed or over the course of pregnancy. The daily net requirements of Ca, P and Mg for maintenance were 60.4, 31.1 and 2.42 mg/kg live BW (LBW), respectively. The daily net Na requirement for maintenance was greater in Saanen goats (11.8 mg/kg LBW) than in Oberhasli goats (8.96 mg/kg LBW; P<0.05). Daily net K requirements increased as pregnancy progressed from 8.73 to 15.4 mg/kg LBW (P<0.01). The findings of this study will guide design of diets with adequate mineral content for pregnant goats throughout their pregnancy.

Intravenous maternal -arginine administration to twin-bearing ewes during late pregnancy enhances placental growth and development

This study aimed to investigate if intravenous maternal Arg administration to well-fed twin-bearing ewes, from 100 to 140 d of gestation or birth, could enhance placental development and placental nutrient transport. Ewes received intravenous infusions of saline (control) or 345 μmol Arg HCl/kg of BW 3 times daily from d 100 of pregnancy (P100) to d 140 of pregnancy (P140; cohort 1) or from P100 to birth (cohort 2). At P140, ewes in cohort 1 were euthanized and individual placentae per fetus were dissected and placentomes were classed per type (A to D) and size (light to heavy). Placentome number and individual weight were recorded. As an indicator of placental nutrient transport, blood plasma was collected from the uterine ovarian vein (UOV), uterine artery (UA), and umbilical vein and artery at the time of euthanasia and analyzed for metabolites and free AA concentrations. The ewes in cohort 2 were allowed to lamb and lambs were weighed at birth. The expelled placenta was dissected and number of cotyledons and weights of total cotyledons, remaining fetal membranes, and total placenta were recorded. At P140, Arg-infused ewes had a 63% ( = 0.03) greater number of unoccupied caruncles than control ewes. No differences were observed for placental weight at P140. At birth, lambs from Arg-infused ewes tended to have 11% ( = 0.09) greater placental weight and 34% ( = 0.03) greater total cotyledon weight compared with control lambs. Arginine-infused ewes (Arg-infused) had increased concentrations of Arg ( = 0.0001) and ornithine (Orn; = 0.004) but decreased concentrations of Met ( = 0.01) and His ( = 0.02 and = 0.09, respectively) compared with control ewes in plasma UOV and UA. Fetuses from Arg-infused ewes had increased concentrations of Orn ( = 0.005) and decreased concentrations of His ( = 0.006), Met ( = 0.003), and Lys ( = 0.01) but no differences in Arg ( > 0.10) concentrations were found compared with control fetuses in umbilical artery and vein plasma. This study showed that maternal Arg administration of well-fed twin-bearing ewes during late pregnancy tended to improve placental growth and development.

N-carbamylglutamate and L-arginine improved maternal and placental development in underfed ewes

The objectives of this study were to determine how dietary supplementation ofN-carbamylglutamate (NCG) and rumen-protected L-arginine (RP-Arg) in nutrient-restricted pregnant Hu sheep would affect (1) maternal endocrine status; (2) maternal, fetal, and placental antioxidation capability; and (3) placental development. From day 35 to day 110 of gestation, 32 Hu ewes carrying twin fetuses were allocated randomly into four groups: 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations, 50% of NRC recommendations supplemented with 20g/day RP-Arg, and 50% of NRC recommendations supplemented with 5g/day NCG product. The results showed that in maternal and fetal plasma and placentomes, the activities of total antioxidant capacity and superoxide dismutase were increased (P<0.05); however, the activity of glutathione peroxidase and the concentration of maleic dialdehyde were decreased (P<0.05) in both NCG- and RP-Arg-treated underfed ewes. The mRNA expression of vascular endothelial growth factor and Fms-like tyrosine kinase 1 was increased (P<0.05) in 50% NRC ewes than in 100% NRC ewes, and had no effect (P>0.05) in both NCG- and RP-Arg-treated underfed ewes. A supplement of RP-Arg and NCG reduced (P<0.05) the concentrations of progesterone, cortisol, and estradiol-17β; had no effect on T4/T3; and improved (P<0.05) the concentrations of leptin, insulin-like growth factor 1, tri-iodothyronine (T3), and thyroxine (T4) in serum from underfed ewes. These results indicate that dietary supplementation of NCG and RP-Arg in underfed ewes could influence maternal endocrine status, improve the maternal–fetal–placental antioxidation capability, and promote fetal and placental development during early-to-late gestation.

Catabolism and safety of supplemental L-arginine in animals

L-arginine (Arg) is utilized via multiple pathways to synthesize protein and low-molecular-weight bioactive substances (e.g., nitric oxide, creatine, and polyamines) with enormous physiological importance. Furthermore, Arg regulates cell signaling pathways and gene expression to improve cardiovascular function, augment insulin sensitivity, enhance lean tissue mass, and reduce obesity in humans. Despite its versatile roles, the use of Arg as a dietary supplement is limited due to the lack of data to address concerns over its safety in humans. Data from animal studies are reviewed to assess arginine catabolism and the safety of long-term Arg supplementation. The arginase pathway was responsible for catabolism of 76-85 and 81-96 % Arg in extraintestinal tissues of pigs and rats, respectively. Dietary supplementation with Arg-HCl or the Arg base [315- and 630-mg Arg/(kg BW d) for 91 d] had no adverse effects on male or female pigs. Similarly, no safety issues were observed for male or female rats receiving supplementation with 1.8- and 3.6-g Arg/(kg BW d) for at least 91 d. Intravenous administration of Arg-HCl to gestating sheep at 81 and 180 mg Arg/(kg BW d) is safe for at least 82 and 40 d, respectively. Animals fed conventional diets can well tolerate large amounts of supplemental Arg [up to 630-mg Arg/(kg BW d) in pigs or 3.6-g Arg/(kg BW d) in rats] for 91 d, which are equivalent to 573-mg Arg/(kg BW d) for humans. Collectively, these results can help guide studies to determine the safety of long-term oral administration of Arg in humans.

Nutritional plane of twin-bearing ewes alters fetal mammary gland biochemical composition and mTOR/MAPK pathway signaling

Identifying the biochemical changes and molecular pathways that regulate fetal mammary development in response to maternal nutrition is important for understanding the link between fetal programming of mammary development and future lactation performance. Although there are published studies regarding biochemical changes in the developing mammary gland, there are currently no data on molecular pathway involvement in regulating ruminant fetal mammary development. This study investigated changes in fetal mammary biochemical indices and mechanistic target of rapamycin (mTOR)/mitogen activated protein kinase (MAPK) signaling at d 100 and 140 of gestation in an ovine model of restricted maternal nutrition. Ewes were randomly allocated to ad libitum (A) or maintenance (M) nutritional regimens, under New Zealand pastoral grazing conditions, from d 21 to 140 of pregnancy. At d 100 and 140 of pregnancy, a subgroup of twin-bearing dams was euthanized, and whole fetal mammary glands (fiber, skin, fat, and ducts) were collected. Mammary glands of fetuses carried by M-fed dams were heavier at d 100 than those of fetuses carried by A-fed dams ( = 0.03), with no difference in the abundance of mTOR/MAPK signaling proteins observed. At d 140, mammary glands of fetuses carried by M-fed dams were lighter ( = 0.07) than fetuses carried by A-fed dams because of decreased hyperplasia ( = 0.04) and hypertrophy ( = 0.09) but had increased protein synthetic capacity ( = 0.02). Increased protein synthetic capacity was associated with increased abundance of MAPK pathway signaling proteins eukaryotic intiation factor 4E (eIF4E)/eIF4E and mTOR pathway signaling proteins eukaryotic initiation factor 4E-binding protein 1 (4E-BP1)/4E-BP1 and ribosomal protein S6 (RPS6)/RPS6 ( ≤ 0.05). Increased abundance of MAPK/mTOR pathway proteins is proposed to mediate increased protein synthetic capacity via ribosome biogenesis and the availability of factors required to initiate protein translation. The primary regulator of 4E-BP1 phosphorylation at Ser65 and RPS6 at Ser235/236 is the activated form of mTOR: mTOR. To study potential tissue-specific mTOR, mTOR abundance mammary glands, separated into parenchyma and fat pad, were collected from d 140 fetuses carried by dams fed a lucerne-based pellet diet formulated to meet 100% of the NRC-recommended maintenance requirements. Results showed that the abundance of mTOR was primarily localized to the fat pad, indicating that the fat pad plays a potential role in regulating development of the fetal mammary gland.

Supplementation with rumen-protected L-arginine-HCl increased fertility in sheep with synchronized estrus

The aim of the present study was to evaluate the effects of L-arginine-HCl supplementation on ovulation rate, fertility, prolificacy, and serum VEGF concentrations in ewes with synchronized oestrus. Thirty Suffolk ewes with a mean body weight of 45 ± 3 kg and a mean body condition score (BCS) of 2.4 ± 0.28 were synchronized for estrus presentation with a progestin-containing sponge (20 mg Chronogest® CR) for 9 days plus PGF2-α (Lutalyse; Pfizer, USA) on day 7 after the insertion of the sponge. The ewes were divided into two groups; i.e., a control group (n = 15) that was fed on the native pasture (basal diet) and an L-arginine-HCl group (n = 15) that received 7.8 g of rumen-protected L-arginine-HCl from day 5 of the sponge insertion until day 25 after mating plus the basal diet. The L-arginine-HCl was administered daily via an esophageal probe between days 5 and 9 of the synchronization protocol and every third day subsequently. Blood samples were drawn from the jugular vein every 6 days throughout the entire experimental period. The results revealed that the L-arginine-HCl supplementation increased fertility during the synchronized estrus (P = 0.05). However, no effects were observed on the final BCS (P = 0.78), estrus presentation (P = 0.33), multiple ovulations (P = 0.24), prolificacy (P = 0.63), or serum VEGF concentration. In conclusion, L-arginine-HCl supplementation during the period used in this study increased fertility in sheep with synchronized estrus possibly due to improved embryo-fetal survival during early pregnancy.

Formate metabolism in fetal and neonatal sheep

By virtue of its role in nucleotide synthesis, as well as the provision of methyl groups for vital methylation reactions, one-carbon metabolism plays a crucial role in growth and development. Formate, a critical albeit neglected component of one-carbon metabolism, occurs extracellularly and may provide insights into cellular events. We examined formate metabolism in chronically cannulated fetal sheep (gestation days 119-121, equivalent to mid-third trimester in humans) and in their mothers as well as in normal full-term lambs. Plasma formate levels were much higher in fetal lamb plasma and in amniotic fluid (191 ± 62 and 296 ± 154 μM, respectively) than in maternal plasma (33 ± 13 μM). Measurements of folate, vitamin B12, and homocysteine showed that these high formate levels could not be due to vitamin deficiencies. Elevated formate levels were also found in newborn lambs and persisted to about 8 wk of age. Formate was also found in sheep milk. Potential precursors of one-carbon groups were also measured in fetal and maternal plasma and in amniotic fluid. There were very high concentrations of serine in the fetus (∼1.6 mM in plasma and 3.5 mM in the amniotic fluid) compared with maternal plasma (0.19 mM), suggesting increased production of formate; however, we cannot rule out decreased formate utilization. Dimethylglycine, a choline metabolite, was also 30 times higher in the fetus than in the mother.

Improving amino acid nutrition to prevent intrauterine growth restriction in mammals

Intrauterine growth restriction (IUGR) is one of the most common concerns in human obstetrics and domestic animal production. It is usually caused by placental insufficiency, which decreases fetal uptake of nutrients (especially amino acids) from the placenta. Amino acids are not only building blocks for protein but also key regulators of metabolic pathways in fetoplacental development. The enhanced demands of amino acids by the developing conceptus must be met via active transport systems across the placenta as normal pregnancy advances. Growing evidence indicates that IUGR is associated with a reduction in placental amino acid transport capacity and metabolic pathways within the embryonic/fetal development. The positive relationships between amino acid concentrations in circulating maternal blood and placental amino acid transport into fetus encourage designing new therapies to prevent or treat IUGR by enhancing amino acid availability in maternal diets or maternal circulation. Despite the positive effects of available dietary interventions, nutritional therapy for IUGR is still in its infancy. Based on understanding of the underlying mechanisms whereby amino acids promote fetal growth and of their dietary requirements by IUGR, supplementation with functional amino acids (e.g., arginine and glutamine) hold great promise for preventing fetal growth restriction and improving health and growth of IUGR offspring.

The effects of diet and arginine treatment on serum metabolites and selected hormones during the estrous cycle in sheep

The aim of this study was to determine the effects of diet and arginine (Arg) treatment on serum concentrations of selected metabolites and metabolic and reproductive hormones in nonpregnant ewes. Sixty days before the onset of estrus (Day 0), Rambouillet ewes were randomly assigned to one of three dietary groups: maintenance control (C; N = 16; 100% National Research Council requirements), overfed (O; N = 16; 2 × C), or underfed (U; N = 16, 0.6 × C) to achieve and maintain three different body conditions during their estrous cycle(s). At Day 0, ewes from each nutritional group were randomly assigned to receive one of two treatments: saline (Sal) or Arg (L-Arg-HCl; 155 μmol Arg per kg of body weight [BW]; intravenous), which was administered three times per day for 21 or 26 days. Blood samples were collected on Days 0, 6, 10, 12, 16, 21, and 26 of Sal or Arg treatment for evaluation of Arg, nitric oxide metabolite, cholesterol, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone. For a time-response trial, blood samples were collected at 0, 1, 2, 4, and 7 hours after Sal or Arg treatment at the mid-luteal phase to determine serum Arg concentrations. During the 11-week study, C maintained body weight, O gained 9.6 ± 0.7 kg, and U lost 13.9 ± 0.1 kg. Overall, serum concentrations of Arg, glucose, insulin, insulin-like growth factor 1, leptin, and progesterone were greater (P < 0.05) in O ewes than C and/or U ewes and were not affected by Arg treatment. Serum Arg concentration increased at 1 and 2 hours and decreased to basal level at 4 and 7 hours after Arg treatment. These data reinforce the importance of diet in regulation of metabolic and endocrine functions, and demonstrated that the dose and duration of Arg treatment used in this study does not alter serum metabolites or hormones in nonpregnant ewes of various nutritional planes.