Glucose homeostasis and metabolic adaptation in the pregnant and lactating sheep are affected by the level of nutrition previously provided during her late fetal life

Promotion of Pregnant Merino Ewes' Welfare with the Introduction of a Drought- and High-Temperature-Resistant Cereal into Their Diet: Analysis of Tritordeum Meadow

Tritordeum is a new cereal resistant to drought and high temperatures, and it is a very healthy crop. The aim of this study was to compare two different diets (tritordeum meadow vs. oat meadow) for grazing pregnant ewes to determine if there was any effect on the objective physiological indicators of animal welfare. A total of 150 pregnant Merino ewes (3-5 years) were randomly divided into two groups (n = 75 each) to be fed with two different meadows, being evaluated during the spring season. Red blood cells count, haemoglobin, packed cell volume, white blood cell count, neutrophiles/lymphocytes ratio, lactate dehydrogenase, creatinine phosphokinase, aspartate aminotransferase, glucose, cortisol, total plasma proteins, albumin, globulins, albumin/globulins ratio, alkaline phosphatase, glutamate dehydrogenase, IgA, and IgG were determined. Overall, the results of this study indicate that the welfare of pregnant ewes fed with tritordeum meadow was better than that of pregnant ewes fed with oat meadow. Tritordeum meadow had a positive influence on the physiological parameters of animal welfare studied in pregnant Merino ewes. Therefore, tritordeum meadow can be considered a functional feed, as it has a beneficial effect on health beyond its basic nutritional value. Farmers are recommended to feed a cereal such as tritordeum grassland to their sheep, as it not only ensures that the animals benefit from all the nutrients, but also prevents diseases and improves their quality of life. In addition, the cereal's resistance to fungal diseases makes it suitable for use in sustainable production systems with a reduced environmental footprint.

Postpartum Body Condition Score (BCS) and Lactation Stage (30 and 60 Days) Affecting Essential Fatty Acids (EFA) and Milk Quality of Najdi Sheep

Body condition scoring (BCS) can be used to assess the energy reserves of sheep during feeding, production, and weaning. The aim of this study was to evaluate the influence of BCS after parturition in stages of lactation (30 and 60 days) on the milk quality of Najdi ewes. The ewes were milked in the morning after their lambs had been isolated. Milk composition and fatty acid profiles (FA) were analyzed at 30 and 60 days of lactation after assessment of the sheep's body condition. The sheep were classified into the following body conditions: 2.5, 3.0, 3.5, and 4.0. Sheep milk contained significant (p < 0.05) levels of protein at a BCS of 3.5 and on day 60 of lactation. The ewes with a BCS of 2.5 had a high milk content (p < 0.05) of unsaturated fatty acids (USFA), monounsaturated fatty acid (MUFA), oleic acid (OA), vaccenic acid (VA), and LA at day 60 of lactation. This result shows that the ewes with a BCS of 2.5 were able to produce high-quality milk, and 60 days of lactation was the preferred time for producing good milk and tasty and healthy dairy products.

Prenatal exposure to different diets influences programming of glucose and insulin metabolism in dairy ewes

Nutrition in fetal and postnatal life can influence the development of several biological systems, with permanent effects in adult life. The aim of this work was to investigate in dairy sheep whether diets rich in starch or fiber during intrauterine life (75 d before lambing) and postnatal life (from weaning to first pregnancy; growth phase) program glucose and insulin metabolism in the female offspring during their first pregnancy. Starting from intrauterine life, 20 nulliparous Sarda ewes were exposed to 4 dietary regimens (n = 5 per group) based on different dietary carbohydrates during their intrauterine life and their subsequent growth phase: (1) the fiber (FI) diet during both intrauterine and growth life, (2) the starch (ST) diet during both intrauterine and growth life, (3) the FI diet in intrauterine life followed by the ST diet in the growth phase, and (4) the ST diet in intrauterine life followed by the FI diet in the growth phase. After the end of the growth phase, all growing ewes were fed the same diet and naturally mated. When ewes were pregnant, on average at 124 ± 2 d of gestation they were challenged with an intravenous glucose tolerance test, and peripheral concentrations of glucose and insulin were determined. Basal insulin concentrations were higher in ewes exposed to the ST diet (0.97 μg/L) than in ewes exposed to the FI diet (0.52 μg/L) in intrauterine life. After glucose infusion, glucose and insulin concentrations were not affected by intrauterine diet. Insulin resistance, determined by the homeostasis model assessment, was affected by the intrauterine × growth phases interaction. Insulin sensitivity, assessed by the quantitative insulin check index, was lower in ewes exposed to the ST diet than in those exposed to the FI diet in intrauterine life (ST = 0.28; FI = 0.30). Diet in growth life had no effect on glucose and insulin metabolism. In conclusion, starchy diets offered during intrauterine life but not during postnatal life increased basal insulin level and lowered insulin sensitivity during the first pregnancy. Nutritional strategies of metabolic programming should consider that exposure to starchy diets in late fetal life might favor the programming of dietary nutrient partitioning toward organs with high requirements, such as the gravid uterus or the mammary gland.

The effects of leptin on plasma concentrations of prolactin, growth hormone, and melatonin vary depending on the stage of pregnancy in sheep

The effects of hyperleptinemia and leptin resistance during gestation are unclear. Leptin, an important neuroendocrine regulator, has anorexic effects, but its interactions with other metabolic hormones during pregnancy are unclear. We examined potential roles of leptin in regulating prolactin (PRL), GH, and melatonin plasma concentrations during pregnancy in Polish Longwool ewes. Twelve estrus-synchronized ewes carrying twins after mating were randomly assigned to receive i.v. injections of saline or recombinant ovine leptin (2.5 or 5.0 µg/kg BW). Blood samples were collected (15-min intervals over 4 h) immediately before the first injection at dusk and kept under red light. Treatments were repeated at 2-wk intervals, starting before mating and continuing from days 30 to 135 of gestation. Concentrations of plasma PRL, GH, and melatonin were determined using a validated RIA. The effects of leptin on hormone plasma concentrations varied depending on pregnancy stage and leptin dose. PRL plasma concentrations were affected at most stages of pregnancy and before gestation. In non-, very early- (day 30), and late- (day 120 and 135) pregnant ewes, exogenous leptin stimulated PRL (P < 0.001) plasma concentrations, while during the second month of gestation, it decreased PRL concentrations (P < 0.01). Leptin affected GH plasma concentrations (P < 0.05) only during the first 2 mo of pregnancy, with no effects during the second part of gestation or before pregnancy. In early-pregnant ewes (day 30 and 45), leptin decreased melatonin plasma concentrations (P < 0.05), but at day 60, leptin stimulated melatonin plasma concentrations at low (P < 0.01) and high doses (P < 0.05), with no effects in ewes after 105 d of gestation. These data indicate specific pregnancy-induced endocrine adaptations to changes in energy homeostasis, supporting the hypothesis that leptin affects PRL, GH, and melatonin release during gestation.

Impacts of prenatal nutrition on animal production and performance: a focus on growth and metabolic and endocrine function in sheep

The concept of foetal programming (FP) originated from human epidemiological studies, where foetal life nutrition was linked to health and disease status later in life. Since the proposal of this phenomenon, it has been evaluated in various animal models to gain further insights into the mechanisms underlying the foetal origins of health and disease in humans. In FP research, the sheep has been quite extensively used as a model for humans. In this paper we will review findings mainly from our Copenhagen sheep model, on the implications of late gestation malnutrition for growth, development, and metabolic and endocrine functions later in life, and discuss how these implications may depend on the diet fed to the animal in early postnatal life. Our results have indicated that negative implications of foetal malnutrition, both as a result of overnutrition and, particularly, late gestation undernutrition, can impair a wide range of endocrine functions regulating growth and presumably also reproductive traits. These implications are not readily observable early in postnatal life, but are increasingly manifested as the animal approaches adulthood. No intervention or cure is known that can reverse this programming in postnatal life. Our findings suggest that close to normal growth and slaughter results can be obtained at least until puberty in animals which have undergone adverse programming in foetal life, but manifestation of programming effects becomes increasingly evident in adult animals. Due to the risk of transfer of the adverse programming effects to future generations, it is therefore recommended that animals that are suspected to have undergone adverse FP are not used for reproduction. Unfortunately, no reliable biomarkers have as yet been identified that allow accurate identification of adversely programmed offspring at birth, except for very low or high birth weights, and, in pigs, characteristic changes in head shape (dolphin head). Future efforts should be therefore dedicated to identify reliable biomarkers and evaluate their effectiveness for alleviation/reversal of the adverse programming in postnatal life. Our sheep studies have shown that the adverse impacts of an extreme, high-fat diet in early postnatal life, but not prenatal undernutrition, can be largely reversed by dietary correction later in life. Thus, birth (at term) appears to be a critical set point for permanent programming in animals born precocial, such as sheep. Appropriate attention to the nutrition of the late pregnant dam should therefore be a priority in animal production systems.

Physiological changes in the peri-partum period and colostral IgG transfer in prolific D'man sheep: effects of parity and litter size

The aim of this work was to assess maternal and neonatal changes in plasma proteins, glucose and cortisol and to quantify the colostral immunoglobulin G (IgG) transfer in the peri-partum period in D'man sheep, a prolific breed, taking into account the parity of the ewe. The concentrations of proteins and glucose were high in the ewes on day 7 and at lambing before decreasing. Likewise, cortisol plasma concentration was maximal during the 6 h following lambing and dropped at 12 h. Protein and glucose concentrations were low in lambs at 1 h of birth after which they increased. By contrast, cortisol level was the highest during the first 12 h of birth and then decreased. The colostral IgG level was high at lambing and dropped by over 87 % from 1 to 48 h post-partum. In the newborn, the plasma IgG concentration was lowest at birth and increased rapidly during the first 24 h of birth. Parity influenced maternal physiology with multiparous ewes having the lowest concentrations of proteins, glucose, IgG and cortisol, but the highest colostrum IgG level. Accordingly, lambs born from primiparous ewes had lower protein, glucose and plasma IgG concentrations than lambs born from multiparous ewes. The main outcome of this study was that lambs born from primiparous ewes are characterized by the lowest physiological indices and this may influence their survival chance.

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

The objective of this study was to investigate the effects of maternal protein or energy restriction on hormonal and metabolic status of pregnant goats during late gestation and their postnatal male kids. Forty-five pregnant goats were fed a control (CON), 40% protein-restricted (PR) or 40% energy-restricted (ER) diet from 90 days of gestation until parturition. Plasma of mothers (90, 125 and 145 days of gestation) and kids (6 weeks of age) were sampled to determine metabolites and hormones. Glucose concentration for pregnant goats subjected to PR or ER was less (P < 0.001) than that of CON goats at 125 and 145 days of gestation. However, plasma nonesterified fatty acids concentration was greater (P < 0.01) at 125 and 145 days for PR and ER than CON. Protein restriction increased (P < 0.01) maternal cortisol concentration by 145 days of gestation, and ER decreased (P < 0.01) maternal insulin concentration at 125 days of gestation. Moreover, maternal amino acid (AA) concentrations were affected by nutritional restriction, with greater (P < 0.05) total AA (TAA) and nonessential AA (NEAA) for PR goats but less (P < 0.05) TAA and NEAA for ER goats at 125 days of gestation. After 6 weeks of nutritional recovery, plasma concentrations of most metabolic and hormonal parameters in restricted kids were similar to CON kids, except for reduced (P < 0.05) insulin concentration in ER, and reduced (P < 0.05) Asp concentration in PR and ER kids. These results provide information on potential metabolic mechanisms responsible for fetal programming.

Pancreatic insulin release and peripheral insulin sensitivity in German black headed mutton and Finish Landrace ewes: evaluation of the role of insulin resistance in the susceptibility to ovine pregnancy toxemia

German black headed mutton (GBM) ewes are recognized as being highly susceptible to ovine pregnancy toxemia (OPT). The present trial was performed to evaluate whether a breed-dependent gestational diabetes mellitus-like insulin resistance during late pregnancy might be responsible for the high incidence of OPT in the GBM breed. Modified frequently sampled intravenous glucose tolerance tests (300 mg glucose and 0.03 IU insulin per kg of BW) were performed during mid and late pregnancy, the periparturient, and the dry period in polytocous 3.5-yr-old GBM and Finnish Landrace (FL) ewes fed according to their requirements. The corresponding blood samples were analyzed for plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFAs) and β-hydroxybutyrate (β-HB). In addition, the baseline plasma cortisol concentrations were determined during late pregnancy. The BW gain during pregnancy and the rearing success did not differ between the GBM and FL ewes. In both breeds, late pregnancy was associated with decreased basal plasma glucose concentrations and enhanced glucose disposal, as well as elevated baseline β-HB values. Only in the GBM ewes did the plasma NEFA concentrations increase significantly during advancing pregnancy. Moreover, significantly higher baseline plasma NEFA concentrations as well as lower (P < 0.05) basal plasma glucose values were recorded during late pregnancy in the GBM than in the FL ewes. The first-phase insulin secretion, the peripheral insulin sensitivity, and the baseline plasma cortisol values did not differ between both breeds during late pregnancy. It is concluded that increased lipolysis during late pregnancy is a characteristic of the GBM breed. Moreover, elevated plasma NEFA concentrations may contribute to impaired pancreatic insulin response and peripheral insulin resistance in GBM ewes and thus promote OPT.

The pancreas is altered by in utero androgen exposure: implications for clinical conditions such as polycystic ovary syndrome (PCOS)

Using an ovine model of polycystic ovary syndrome (PCOS), (pregnant ewes injected with testosterone propionate (TP) (100 mg twice weekly) from day (d)62 to d102 of d147 gestation (maternal injection - MI-TP)), we previously reported female offspring with normal glucose tolerance but hyperinsulinemia. We therefore examined insulin signalling and pancreatic morphology in these offspring using quantitative (Q) RT-PCR and western blotting. In addition the fetal pancreatic responses to MI-TP, and androgenic and estrogenic contributions to such responses (direct fetal injection (FI) of TP (20 mg) or diethylstilbestrol (DES) (20 mg) at d62 and d82 gestation) were assessed at d90 gestation. Fetal plasma was assayed for insulin, testosterone and estradiol, pancreatic tissue was cultured, and expression of key β-cell developmental genes was assessed by QRT-PCR. In female d62MI-TP offspring insulin signalling was unaltered but there was a pancreatic phenotype with increased numbers of β-cells (P<0.05). The fetal pancreas expressed androgen receptors in islets and genes involved in β-cell development and function (PDX1, IGF1R, INSR and INS) were up-regulated in female fetuses after d62MI-TP treatment (P<0.05-0.01). In addition the d62MI-TP pancreas showed increased insulin secretion under euglycaemic conditions (P<0.05) in vitro. The same effects were not seen in the male fetal pancreas or when MI-TP was started at d30, before the male programming window. As d62MI-TP increased both fetal plasma testosterone (P<0.05) and estradiol concentrations (P<0.05) we assessed the relative contribution of androgens and estrogens. FI-TP (commencing d62) (not FI-DES treatment) caused elevated basal insulin secretion in vitro and the genes altered by d62MI-TP treatment were similarly altered by FI-TP but not FI-DES. In conclusion, androgen over-exposure alters fetal pancreatic development and β-cell numbers in offspring. These data suggest that that there may be a primary pancreatic phenotype in models of PCOS, and that there may be a distinct male and female pancreas.

Post-glucose load changes of plasma key metabolite and insulin concentrations during pregnancy and lactation in ewes with different susceptibility to pregnancy toxaemia

Insulin resistance during late gestation may act as a predisposing factor of ovine pregnancy toxaemia (OPT). To evaluate the insulin action on energy metabolism in ewes with different susceptibilities to OPT, intravenous glucose tolerance tests (1 mmol glucose/kg body weight) were performed in 5.6 ± 0.7 year old, slightly underfed German Blackheaded Mutton ewes [high-risk (HR) ewes] and 2.5 year old, overnourished Finnish Landrace ewes [low-risk (LR) ewes] during mid and late pregnancy, during early lactation and during the dry period. Plasma samples were analysed for glucose, insulin, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (β-HB). The glucose elimination rate and the glucose-stimulated first-phase insulin secretion were significantly (p < 0.05) lower in the HR, in relation to the LR group combining the data of all gestational stages. The basal rate of lipolysis was significantly increased in the HR ewes during late pregnancy, but the NEFA clearance after the glucose load was similar in both groups during all reproductive stages. Plasma β-HB concentrations decreased only in the LR ewes after the glucose load during late pregnancy. Results indicate an insulin resistance in the HR ewes regarding the glucose utilization and the ketone body formation during late pregnancy. The insulin resistance in the HR ewes may represent one predisposing factor responsible for the susceptibility to OPT. Further scientific work is necessary to elucidate whether this insulin resistance was due to breed, age or nutritional state.

Correlação entre cálcio e insulina durante o teste de tolerância à glicose em ovelhas gestantes e não gestantes

Compararam-se as concentrações de cálcio, glicose e insulina em ovelhas gestantes e não gestantes submetidas ao teste de tolerância à glicose (TTG). Oito ovelhas gestantes (GG) e oito não gestantes (NG) foram submetidas ao TTG por meio da administração endovenosa de uma solução de glicose, na dose de 500mg/kg de peso vivo. Amostras de sangue foram coletadas nos tempos de -15, zero, 15, 30, 45, 60, 90, 120, 150 e 180 minutos, sendo zero min o momento da infusão, para avaliação da concentração sanguínea de glicose, cálcio e insulina. Foi avaliada a taxa de metabolização de glicose e insulina, por meio do cálculo da área sob a curva (ASC). As concentrações de glicose, cálcio, insulina e a ASC da insulina não diferiram entre os grupos (P>0,05), entretanto as três últimas ASCs da glicose foram mais elevados nas gestantes (P<0,05), que correspondem ao período entre 90 e 180min. O teste de correlação de Pearson revelou correlação negativa entre concentração de cálcio e insulina nas gestantes (P<0,05). Estes resultados indicam menor taxa de metabolização de glicose em ovelhas gestantes e uma possível relação de cálcio e insulina no terço final de gestação.

Effects of ewe size and nutrition during pregnancy on glucose metabolism, fat metabolism and adrenal function of postpubertal female twin offspring

Little is known about the long-term metabolic effects of maternal constraint on the offspring and whether a possible interaction of dam size and nutrition during gestation exists, affecting postnatal metabolic functions in the offspring. Four hundred and fifty heavy (H) (60.8 ± 0.18 kg) and 450 light (L) (42.5 ± 0.17 kg) Romney dams were allocated to ad libitum (A) or maintenance (M) nutritional regimens under New Zealand pastoral grazing conditions, from Day 21 to 140 after insemination. One week before lambing, all dams and offspring were managed as one group and provided with ad libitum feeding. At 16 months of age, female twin-born offspring (n = 12 per size by nutrition group) were catheterised and given intravenous insulin (0.15 IU/kg) (ITT), glucose (0.17 g/kg) (GTT) and epinephrine (1 μg/kg) (ETT) challenges to assess their glucose and fat metabolism and adrenal function. No effects of dam size or interactions between dam size and dam nutrition were found on glucose or fat metabolism or adrenal function. In response to the ETT, M-dam offspring showed greater (P < 0.05) peak glucose concentrations, increased (P < 0.05) glucose area under the curve and tended (P < 0.10) to have increased maximum change in glucose and non-esterified free fatty acid concentrations compared with A-ewes. No effects of dam nutrition were found on glucose tolerance, insulin resistance or adrenal function in response to GTT and ITT. In conclusion, dam size had no effect on glucose metabolism, adrenal function or fat metabolism in 16-month-old female twin offspring. Dam nutrition during pregnancy from Day 21 to 140 had no major effect on glucose metabolism, adrenal function or lipolysis; however, it did potentially affect gluconeogenesis and/or glycogenolysis, as increased glucose concentrations in ewes born to M-fed dams were observed in response to ETT. These results indicate that M-ewes could have an advantage over A-ewes in physiological stressful situations in life (e.g. pregnancy, lactation) as their liver may be able to supply more glucose to support their growing conceptus and milk production to increase the chances of survival of their offspring.