Underfed Ewes Research Articles

Reproductive development of male lambs born to undernourished mothers supplemented or not with concentrate during gestation

Southern Patagonia offers harsh environmental and nutritional conditions for sheep pregnancy, which may compromise the fetal and postnatal development of lambs. The aim of the study was to compare the sexual behavior and attractiveness, and semen production and quality during the first year of life of ram lambs born to undernourished mothers grazing on natural pastures, supplemented or not with a concentrate. The study was performed under extensive Patagonian conditions, and a supplement was provided from day 44 of gestation until lambing. Twelve ram lambs born to supplemented ewes (group Sup) and 12 born to control underfed ewes (group Con) were used. Both groups of male lambs remained in a common paddock before and after weaning at 4 months-old. Sexual behavior and attractiveness, and semen production and quality of ram lambs were evaluated when they were 6 and 12 months-old. Sup lambs were heavier than Con at birth, and tended to maintain this difference when they were 4 mo-old; afterward, this difference disappeared. At 6 months-old, Con ram lambs displayed greater sexual activity when individually exposed to an estrous ewe, as well as a trend to a greater sperm concentration. Differences between groups in sexual behavior decreased at 12 months-old, and no differences were detected in seminal traits. In conclusion, supplementation of undernourished pregnant ewes with concentrate from mid-pregnancy until lambing slightly impacted the progeny reproductive performance when they were 6 months-old, an effect that was attenuated at 12 months-old. The effects of the nutritional status of pregnant ewes on the reproductive development of the offspring likely were compensated by a greater growth rate during early life before puberty.

Pregnancy but Not Moderate Undernutrition Attenuates Insulin Suppression of Fat Mobilization in Sheep , ,

Nonpregnant and late-pregnant ditocous ewes were fed either to maintain zero energy balance in maternal tissues (fed) or at 50% of this level (underfed) for several weeks. Plasma concentrations of nonesterified fatty acids (NEFA) and glycerol were measured under basal conditions and during infusion of various doses of insulin while maintaining euglycemia (hyperinsulinemic, euglycemic clamp technique). Pregnancy and undernutrition separately increased basal plasma NEFA concentration in an additive manner; plasma glycerol was increased by pregnancy but unaffected by undernutrition. The molar ratio of NEFA to glycerol was significantly greater in underfed ewes. Analysis of dose-response relations between plasma insulin and metabolites during insulin infusions showed that maximally insulin-suppressed concentrations of NEFA and glycerol were significantly greater in pregnant than in nonpregnant ewes but were unaffected by undernutrition. Neither pregnancy nor undernutrition affected the maximally insulin-suppressed NEFA to glycerol ratio, or the plasma insulin concentration for 50% maximal responses to insulin of plasma NEFA, plasma glycerol, or the plasma NEFA to glycerol ratio. Thus, even in ewes at or close to zero energy balance, pregnancy seems to reduce adipose responsiveness but not sensitivity to the antilipolytic effect of insulin. This is another manifestation of the normal development of insulin resistance in maternal tissues during late pregnancy.

Metabolic memory determines oviductal gene expression of underfed ewes during early gestation

Our aim was to investigate the oviduct environment by studying oviduct gene expression after undernutrition in day-5 pregnant ewes with different initial (i) BCS, and its association with the number of embryos recovered. Thirty-six ewes were divided into 2 groups with different iBCS: iBCS ≥2.75 (n = 19; high, H) and iBCS ≤2.25 (n = 17; low, L), and were randomly assigned to two nutritional treatments for 20 days: 1.5 (control, C) or 0.5 (underfed, U) times the daily maintenance requirements. Thus, the final four groups were: high-iBCS control (HC, n = 9), high-iBCS underfed (HU, n = 10), low-iBCS control (LC, n = 9) and low-iBCS underfed (LU, n = 8). Samples of oviduct were collected and the expression of target genes was quantified using real-time PCR. While high-iBCS control ewes presented more ADIPOR1 mRNA than the high-iBCS underfed group (P < 0.05) and low-iBCS control ewes (P = 0.01), high-iBCS underfed group presented higher ADIPOR2 gene expression than low-iBCS underfed ewes (P < 0.01) evidencing a differential oviductal gene expression for these receptors. In high-iBCS ewes, control animals presented higher IGFBP2 gene expression than underfed ewes (P < 0.05), associated these results with a poor oviductal environment. High-iBCS underfed ewes presented higher IGFBP4 gene expression than high-iBCS control ewes (P < 0.05). Stepwise regression models, using various combinations of data on metabolic and reproductive hormones, and oviduct gene expression as independent variables, identified a set of variables that accounted for 75% of the variation in the number of embryos recovered. In conclusion, the oviductal gene expression depends on body reserves and nutritional treatment, and the effect is gene-specific.

Effects of feed restriction and supplementary garlic oil on blood metabolites in ewes.

The effects of garlic oil (GO) on serum fatty acids, lipid profiles and energy-related blood metabolites in feed-restricted fat-tailed ewes were investigated. For this purpose, twenty-eight dry, non-pregnant Makuei ewes (about three years of age; 45.00 ± 2.20 kg of body weight) were assigned randomly to four experimental groups including group 1 receiving basal diet as total mixed ration (TMR) without GO supplementation (control group), group 2 receiving 100% basal diet supplemented with GO (10.00 mg kg-1 BW), group 3 receiving 70.00% basal diet without GO supplementation and group 4 receiving 70.00% basal diet supplemented with GO (10.00 mg kg-1 BW). The main experimental period started eight weeks after performing adaptation and dietary allocations. Feed restriction reduced serum glucose levels along with higher serum levels of non-esterified fatty acids, triacylglycerols, β-hydroxybutyrate, low-density lipoprotein cholesterol, total cholesterol and very low-density of lipoprotein. Following feed restriction, the serum palmitic and oleic acids concentrations were increased. Garlic oil supplementation had a desirable effect on feed-restricted animals through lowering serum BHB and palmitic and oleic acids concentration and increasing the high-density lipoprotein cholesterol levels in the serum. These findings demonstrated that GO had the potential to reduce body-fat mobilization, thereby lowering the risk factors for disorders associated with negative energy balance in underfed ewes in the periparturient period.

Short-, Medium- and Long-Term Metabolic Responses of Adult Meat Ewes Subjected to Nutritional and β-Adrenergic Challenges.

Simple SummaryThe ability of Merinos d’Arles ewes to quickly overcome undernutrition situations by efficiently using their body energy reserves was confirmed in this study. There is potential for a simplified ß-adrenergic challenge protocol helping to identify differences in adaptive capacity among individuals reared and fed under similar conditions in the same flock.Shortage and refeeding situations lead to switches in metabolic pathways induced by undernutrition and body energy reserve (BR) replenishment cycles. In a 122-d experiment, 36 adult Merinos d’Arles ewes were chosen and first accustomed to diet ingredients (i.e., wheat straw, pelleted alfalfa and sugar beet pulp) and the facility environment for 22 d. Then, ewes were randomly assigned to one of three “diet challenge” treatments during 50 d, (control, underfed and overfed; 12 ewes each) corresponding to 100%, 70% or 160% of energy requirements allowances, respectively. Then, a “refeeding challenge” was applied the last 50 d (i.e., diets adjusted with the same ingredients). An individual monitoring of body weight (BW), body condition score (BCS) and energy metabolism was carried out. The last day, a “ß-adrenergic challenge” was applied. Anabolic or catabolic responses were accompanied by synchronized metabolic regulations, leading to contrasting metabolic and BR profiles. Average BW and BCS were higher and lower in overfed and underfed ewes, respectively, which was proportional to lower and higher BR mobilization dynamics. Higher plasma free fatty acids (FFA) were accompanied by lower blood insulin, leptin and glucose levels. After refeeding, a rebound in BW and BCS were observed, and FFA were drastically reduced in underfed ewes. No differences were detected in plasma FFA at the end of the study, but the lipolytic activity was different and contrasted with the adipose tissue mass.

Nutritionally induced tanycytic plasticity in the hypothalamus of adult ewes

The blood–brain barrier regulates the transport of molecules that convey global energetic status to the feeding circuitry within the hypothalamus. Capillaries within the median eminence (ME) and tight junctions between tanycytes lining the third ventricle (3V) are critical components of this barrier. Herein, we tested the hypothesis that altering the plane of nutrition results in the structural reorganization of tanycytes, tight junctions, and capillary structure within the medial basal hypothalamus. Proopiomelanocortin (POMC) neuronal content within the arcuate nucleus of the hypothalamus (ARC) was also assessed to test whether reduced nutritional status improved access of nutrients to the ARC, while decreasing the access of nutrients of overfed animals. Multiparous, nongestating ewes were stratified by weight and randomly assigned to dietary treatments offered for 75 d: 200% of dietary recommendations (overfed), 100% of dietary recommendations (control), or 60% of dietary recommendations (underfed). The number of POMC-expressing neurons within the ARC was increased (P ≤ 0.002) in underfed ewes. Overfeeding increased (P ≤ 0.01) tanycyte cellular process penetration and density compared with control and underfeeding as assessed using vimentin immunostaining. Immunostaining of tight junctions along the wall of the 3V did not differ (P = 0.32) between treatments. No differences were observed in capillary density (P = 0.21) or classification (P ≥ 0.47) within the ME. These results implicate that changes within the satiety center and morphology of tanycytes within the ARC occur as an adaptation to nutrient availability.

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.

Corpora lutea in superovulated ewes fed different planes of nutrition

The corpus luteum (CL) is an ovarian structure which is critical for the maintenance of reproductive cyclicity and pregnancy support. Diet and/or diet components may affect some luteal functions. FSH is widely used to induce multiple follicle development and superovulation. We hypothesized that FSH would affect luteal function in ewes fed different nutritional planes. Therefore, the aim of this study was to determine if FSH-treatment affects (1) ovulation rate; (2) CL weight; (3) cell proliferation; (4) vascularity; (5) expression of endothelial nitric oxide (eNOS) and soluble guanylate cyclase (sGC) proteins; and (6) luteal and serum progesterone (P4) concentration in control (C), overfed (O), and underfed (U) ewes at the early- and mid-luteal phases. In addition, data generated from this study were compared to data obtained from nonsuperovulated sheep and described by Bass et al. Ewes were categorized by weight and randomly assigned into nutrition groups: C (2.14 Mcal/kg; n = 11), O (2xC; n = 12), and U (0.6xC; n = 11). Nutritional treatment was initiated 60 d prior to day 0 of the estrous cycle. Ewes were injected with FSH on day 13–15 of the first estrous cycle, and blood samples and ovaries were collected at early- and mid-luteal phases of the second estrous cycle. The number of CL/ewe was determined, and CL was dissected and weighed. CL was fixed for evaluation of expression of Ki67 (a proliferating cell marker), CD31 (an endothelial cell marker), and eNOS and sGC proteins using immunohistochemistry and image analysis. From day 0 until tissue collection, C maintained, O gained, and U lost body weight. The CL number was greater (P < 0.03) in C and O than U. Weights of CL, cell proliferation, vascularity, and eNOS but not sGC expression were greater (P < 0.001), and serum, but not luteal tissue, P4 concentrations tended to be greater (P = 0.09) at the early- than mid-luteal phase. Comparisons of CL measurements demonstrated greater (P < 0.01) cell proliferation and serum P4 concentration, but less vascularity at the early and mid-luteal phases, and less CL weight at the mid-luteal phase in superovulated than nonsuperovulated ewes; however, concentration of P4 in luteal tissues was similar in both groups. Thus, in superovulated ewes, luteal cell proliferation and vascularity, expression of eNOS, and serum P4 concentration depend on the stage of luteal development, but not diet. Comparison to control ewes demonstrated several differences and some similarities in luteal functions after FSH-induced superovulation.

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.

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

The objectives of this study were to determine how dietary supplementation of N-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.

The effect of maternal nutrition level during the periconception period on fetal muscle development and plasma hormone concentrations in sheep

The effect of maternal nutrition level during the periconception period on the muscle development of fetus and maternal–fetal plasma hormone concentrations in sheep were examined. Estrus was synchronized in 55 Karayaka ewes and were either fed ad libitum (well-fed, WF, n=23) or 0.5×maintenance (under-fed, UF, n=32) 6 days before and 7 days after mating. Non-pregnant ewes (WF, n=13; UF, n=24) and ewes carrying twins (WF, n=1) and female (WF, n=1; UF, n=3) fetuses were removed from the experiment. The singleton male fetuses from well-fed (n=8) and under-fed (n=5) ewes were collected on day 90 of gestation and placental characteristics, fetal BWs and dimensions, fetal organs and muscles weights were recorded. Maternal (on day 7 after mating) and fetal (on day 90 of pregnancy) blood samples were collected to analyze plasma hormone concentrations. Placental characteristics, BW and dimensions, organs and muscles weights of fetuses were not affected by maternal feed intake during the periconception period. Maternal nutrition level did not affect fiber numbers and the muscle cross-sectional area of the fetal longissimus dorsi (LD), semitendinosus (ST) muscles, but the cross-sectional area of the secondary fibers in the fetal LD and ST muscles from the UF ewes were higher than those from the WF ewes (P<0.05). Also, the ratio of secondary to primary fibers in the ST muscle were tended to be lower in the fetuses from the UF ewes (P=0.07). Maternal nutrition level during the periconception period did not cause any significant changes in fetal plasma insulin and maternal and fetal plasma IGF-I, cortisol, progesterone, free T3 and T4 concentrations. However, maternal cortisol concentrations were lower while insulin concentrations were higher in the WF ewes than those in the UF ewes (P<0.05). These results indicate that the reduced maternal feed intake during the periconception period may alter muscle fiber diameter without affecting fiber types, fetal weights and organ developments and plasma hormone concentrations in the fetus.

Periconceptional undernutrition modifies endocrine profiles and hepatic gene expression in sheep.

This study investigated whether a 22-day period of undernutrition (half maintenance) could affect maternal endocrine responses and liver gene expression during early pregnancy (day 7). Thirty-five ewes were fed 1.5 (n=15) or 0.5 (n=20) their maintenance requirements and slaughtered on day 7 of the oestrus cycle or pregnancy (oestrus=day 0). Insulin, IGF, leptin and non-esterified fatty acids (NEFA) were determined on days -14, 0 and 7. Transcripts of the IGF family and adipokines receptors were determined in the liver by real-time RT-PCR. Underfed animals presented lower body weight and body condition, greater plasma concentration of NEFA, and lower plasma concentrations of leptin, insulin and IGF1 compared to adequately fed animals. Underfed ewes presented greater hepatic expression of IGFBP2 than well-fed ewes, but tended to have lesser expression of IGFBP5. While no effect of undernutrition on IGFBP4 and ADIPOR2 mRNA expressions was observed, they were increased by pregnancy in underfed animals. This study shows that undernutrition modifies endocrine profiles and hepatic gene expression of IGFBP2 and 5. The pregnancy status increased hepatic gene expression of IGFBP4 and ADIPOR2 mRNA in undernourished ewes.

Endothelial nitric oxide synthase (eNOS) and soluble guanylyl cyclase (sGC) expression in the ovarian artery during the estrous cycle in overfed or underfed sheep treated with arginine (Arg). (LB324)

The aim of this study was to determine if Arg supplementation to control, overfed, and underfed ewes impacts protein and mRNA expression of eNOS and sGC in the ovarian artery. Ewes were categorized by weight and randomly assigned to one of three different nutrition groups: control (C; 2.14 Mcal/kg; n=37), overfed (O; 2xC Mcal/kg; n=37), and underfed (U; 60% of C Mcal/kg; n=37) beginning 60 days prior to Arg treatment and were randomly assigned to one of two treatments; Arg (L‐Arg‐HCl; 155 µmol Arg/kg BW) or saline (~10 ml) i.v. beginning on day 0 of the first estrous cycle until tissue collection at the late‐luteal phase of the first estrous cycle, or early or mid‐luteal phases of the second estrous cycle. Ovarian vascular pedicle was fixed and imaged, and RNA was extracted from the ovarian artery (OA). Compared to saline controls, Arg increased mRNA expression of eNOS nearly 300‐fold and sGC approximately 150‐fold in OA for O group during the mid‐luteal phase (P&lt;0.0001; n=5 for each group). Arg (n=3) increased eNOS 7‐fold (P&lt;0.06) compared to saline (n=7) in U during the early luteal phase. No other Arg effects were observed in either other diet groups or on other luteal phases. eNOS protein was localized in blood vessel endothelium of the ovarian pedicle, whereas sGC‐beta protein was expressed in both vascular smooth muscle and endothelium of blood vessels. During the early or mid‐luteal phase when the corpus luteum is actively growing or fully functional, Arg can dramatically influence the NO system in OA by increasing mRNA expression of eNOS and sGC in U or O, and suggests that Arg supplementation may alter vascular function and blood flow to the ovary in compromised animals.Supported by USDA‐AFRI grant 2011‐67016‐30174, and Hatch Projects ND01754 and ND01748 to ATGB and DAR.

Overfeeding and underfeeding have detrimental effects on oocyte quality measured by in vitro fertilization and early embryonic development in sheep

To determine effects of maternal diet on in vitro fertilization (IVF) and early embryonic development, ewes (n = 48) were divided into control, overfed (ad libitum feeding), and underfed (60% of control) nutritional planes for 8 wk before oocyte collection. Follicular development was induced by twice-daily injections of FSH on days 13 and 14 of the estrous cycle, and ovaries and blood samples were collected on day 15 of the estrous cycle. During the 8-wk experiment, for control ewes BW and BCS did not change, but for overfed ewes mean (± SEM) BW and BCS increased (11.8 ± 1.1 kg and 2.0 ± 0.1, respectively) and for underfed ewes decreased (14.2 ± 0.9 kg and 0.7 ± 0.1, respectively). The number of follicles was determined; oocytes were collected and subjected to in vitro maturation and fertilization. After IVF, developing embryos were evaluated throughout the 8-d culture period. The proportion of cleaved oocytes after IVF and developing morula and blastocyst were less (P < 0.0001) in overfed and underfed ewes than in control ewes. However, number of visible follicles, total number of oocytes, number of healthy oocytes, and percentage of healthy oocytes were similar for control, overfed, and underfed ewes. Serum insulin concentration was greater (P < 0.05) in overfed ewes than in underfed ewes, estradiol 17-β (E2) concentration was greater (P < 0.05) in underfed ewes than in overfed ewes, but triiodothyronine (T3) and thyroxine (T4) concentrations were similar in all treatment groups. These data show that inadequate feeding has a negative effect on oocyte quality which results in lower oocyte cleavage after IVF and morula and blastocyst formation; overfeeding increased serum insulin and underfeeding increased serum E2 but not T3 or T4. These data emphasize the importance of diet for reproductive and metabolic functions. Furthermore, the mechanisms through which enhanced or decreased energy in diet affect oocyte quality and serum insulin and E2 concentrations remain to be elucidated.

Arginine nutrition and fetal brown adipose tissue development in nutrient-restricted sheep

Intrauterine growth restriction is a significant problem worldwide, resulting in increased rates of neonatal morbidity and mortality, as well as increased risks for metabolic and cardiovascular disease. The present study investigated the role of maternal undernutrition and L-arginine administration on fetal growth and development. Embryo transfer was utilized to generate genetically similar singleton pregnancies. On Day 35 of gestation, ewes were assigned to receive either 50 or 100% of their nutritional requirements. Ewes received i.v. injections of either saline or L-arginine three times daily from Day 100 to Day 125. Fetal growth was assessed at necropsy on Day 125. Maternal dietary manipulation altered circulating concentrations of leptin, progesterone, and amino acids in maternal plasma. Fetal weight was reduced in nutrient-restricted ewes on Day 125 compared with 100% fed ewes. Compared with saline-treated underfed ewes, maternal L-arginine administration did not affect fetal weight but increased weight of the fetal pancreas by 32% and fetal peri-renal brown adipose tissue mass by 48%. These results indicate that L-arginine administration enhanced fetal pancreatic and brown adipose tissue development. The postnatal effects of increased pancreatic and brown adipose tissue growth warrant further study.

Parenteral Administration of L-Arginine Prevents Fetal Growth Restriction in Undernourished Ewes ,

Intrauterine growth restriction (IUGR) is a major health problem worldwide that currently lacks an effective therapeutic solution. This study was conducted with an ovine IUGR model to test the hypothesis that parenteral administration of L-arginine (Arg) is effective in enhancing fetal growth. Beginning on d 28 of gestation, ewes were fed a diet providing 100% (control-fed) or 50% (underfed) of NRC-recommended nutrient requirements. Between d 60 of gestation and parturition, underfed ewes received i.v. infusions of saline or 155 μmol Arg-HCl/kg body weight 3 times daily, whereas control-fed ewes received only saline. The birth weights of lambs from saline-infused underfed ewes were 23% lower (P < 0.01) than those of lambs from control-fed dams. Administration of Arg to underfed ewes increased (P < 0.01) concentrations of Arg (69%), ornithine (55%), proline (29%), methionine (37%), leucine (36%), isoleucine (35%), cysteine (19%), and FFA (43%) in maternal serum, decreased maternal circulating levels of ammonia (18%) and triglycerides (32%), and enhanced birth weights of lambs by 21% compared with saline-infused underfed ewes. There was no difference in birth weights of lambs between the control-fed and the Arg-infused underfed ewes. These novel results indicate that parenteral administration of Arg to underfed ewes prevented fetal growth restriction and provide support for its clinical use to ameliorate IUGR in humans. The findings also lay a new framework for studying cellular and molecular mechanisms responsible for the beneficial effects of Arg in regulating conceptus growth and development. J. Nutr. 140: 1242–1248, 2010.

Early pregnancy alters the metabolic responses to restricted nutrition in sheep

This study investigated whether a 27-day period of nutrition at half-maintenance during early pregnancy (up to Day 14) could alter maternal endocrine responses. Forty-six ewes were fed all or half of their maintenance requirements and slaughtered on Day 14 of the oestrous cycle or pregnancy. We used real time RT-PCR to study gene expression of growth hormone receptor (GHR) and leptin in adipose tissue and GHR, GHR1A and of the insulin-like growth factor I (IGF-I) in the liver. Blood profiles of metabolites and metabolic hormones were also determined. Throughout the experiment, underfed animals presented lower body weight and body condition, greater plasma concentrations of non-esterified fatty acids (NEFA), and lower plasma concentrations of leptin, compared to adequately fed animals. Undernutrition affected the patterns of gene expression in adipose and hepatic tissues, and the responses differed between pregnant and non-pregnant ewes. In adequately fed ewes, pregnancy up-regulated leptin mRNA expression in adipose tissue, a response that was impaired in underfed ewes. The hepatic expression of IGF-I mRNA was increased by pregnancy in underfed animals while no effect was observed in adequately fed ewes. It remains to be determined whether the changes in the endocrine milieu are paralleled by modifications in uterine gene expression that could alter the environment of the embryo during early pregnancy.

Body fat content and feeding level interact strongly in the short- and medium-term regulation of plasma leptin during underfeeding and re-feeding in adult sheep

Circulating leptin is regulated by food intake in the long, medium and short term; however, little is known about putative remnant effects of these successive regulations at any given time. To clarify this, two experiments were conducted in adult sheep, during which body condition parameters and plasma leptin were measured. During experiment 1, twenty ewes with normal body condition were either well fed (101 % of maintenance energy requirements (MER)) or underfed (41 % MER) for 166 d, then rapidly re-fed (at a mean of 208 % MER) for 3 d. Leptinaemia decreased after 14 d of underfeeding, remained depressed until day 166 and did not increase after 3 d re-feeding, whereas it was increased (+153 %; P < 0.05) by re-feeding the previously well-fed ewes. During experiment 2, twenty-four fat or lean ewes were either well fed (114 % MER) or underfed (52 % MER) for 94 d, and gradually re-fed for 2 d and maintained at a high feeding level (235 % MER) for 9 d. Underfeeding decreased leptinaemia in fat (from 4.19 to 2.63 ng/ml) but not lean ewes, and re-feeding increased leptinaemia after 5 d in lean previously well-fed (+123 %; P < 0.05) but not underfed ewes. In fat ewes, the impact of re-feeding was rapid (+144 %; P < 0.001 at 5 d) in previously well-fed ewes, whereas it was more gradual with a maximum at 11 d (+162 %; P < 0.01) in previously underfed ewes. In conclusion, leptinaemia is modulated by short-term energy intake level in interaction with long-term regulations involving nutritional history and body fatness, suggesting that a biological threshold of adiposity (about 20 %) is necessary to allow short- and medium-term leptin regulation.

Endocrine and metabolic factors involved in the effect of nutrition on the production of colostrum in female sheep

We investigated the physiological relationship between diet during pregnancy and colostrum production in ewes to test the hypothesis that for ewes that are in low body condition, with low fat reserves, the food supply will be the main source of energy for colostrum synthesis. To this end, we measured the amount of colostrum accumulated by ewes under two levels of nutrition. We also measured the circulating concentrations of metabolites and hormones associated with lactogenesis (beta-hydroxybutyrate, glucose, progesterone, prolactin, cortisol, growth hormone, leptin, insulin and insulin-like growth factor-I) Ewes were either under-fed at 70 (n = 15) or well-fed at 110% (n = 10) of their daily metabolisable energy requirement during the last two months of pregnancy. Colostrum accumulation up to parturition was 168 +/-48 g for under-fed ewes and 451 +/-103 g for well-fed ewes. After birth, under-fed ewes produced less colostrum than well-fed ewes but the difference was no longer significant. The level of nutrition also influenced the plasma concentrations of hormones and metabolites related to lactogenesis. Progesterone concentrations decreased before lambing in all animals but in under-fed ewes the fall appeared to be too small to initiate the onset of colostrum production. Beta-hydroxybutyrate concentrations were higher in under-fed than in well-fed ewes, suggesting that the under-fed ewes were mobilising more adipose tissue but they still did not meet their ME requirements for colostrum production. We concluded that, in underfed ewes, there are insufficient nutrients for adequate lactation and the hormone regime is inappropriate for good udder development and colostrum synthesis.

Effects of plane of nutrition on in vitro fertilization and early embryonic development in sheep1

Nutrition has been shown to influence several reproductive functions, including hormone production, oocyte competence and fertilization, and early embryonic development. To determine the effects of maternal diet on in vitro fertilization (IVF) and early embryonic development, ewes (n = 18; 47.0 +/- 1.5 kg of initial BW) were divided into control and underfed (60% of control) nutritional planes for 8 wk before oocyte collection. Pelleted diets containing 2.4 Mcal of ME/kg and 13% CP (DM basis) were fed once daily. During the first 4-wk acclimation phase, control and underfed ewes were fed 1,000 and 600 g/d, respectively. From wk 4 to 8, control (adequate) ewes were fed to maintain BW and offered 720 g/d, whereas underfed ewes received 432 g/d (60% restricted). Synchronization of estrus was performed using progestagen sponges for 14 d. Follicular development was induced by twice daily injections of FSH on d 13 (5 units/injection) and 14 (4 units/injection) of the estrous cycle. Oocytes were collected from all visible follicles on d 15 of the estrous cycle. After IVF, the proportion of developing embryos was evaluated throughout an 8-d culture period. Under-nutrition decreased (P < 0.006) the rate of cleavage, number of blastocysts per ewe, and rate of blastocyst formation (from 79 to 64%; from 3.3 to 0.8; and from 31 to 8%, respectively). However, the number of visible follicles, total number of oocytes, number of healthy oocytes, percentage of healthy oocytes, number of cleaved oocytes, and morula formation per ewe were similar for control and underfed ewes. These data indicate that undernutrition of donor ewes, resulting in lower BW and BCS, has a negative effect on oocyte quality, which results in lower rates of cleavage and blastocyst formation.