Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

Foetal programming in sheep: Reproductive and productive implications

The aim of this study was to evaluate the effects of pregnant ewe nutrition on the performance of offspring in terms of meat, wool production, and reproduction. Foetal programming in sheep has focused on several aspects related to foetal growth, postnatal production, behaviour, and immunological performance. Currently, significant efforts are being made to understand the endocrine, metabolic, and epigenetic mechanisms involved in offspring development. Current studies have not only evaluated the foetal period, despite the pre-conception parental nutrition has demonstrated an effect on the foetal, embryonic, and pre-implantation periods and can generate permanent effects in the foetal and postnatal phases. The performance of offspring is the result of interactions between the genome, epigenome, and environmental interventions during conception. Several factors influence the expression of phenotypic characteristics in progenies; however, this study focused on presenting data on the effect of pregnant ewe nutrition alone on foetal growth and the productive aspects of their offspring.

Differing planes of nutrition alter serum and histotroph amino acid composition in nonpregnant, multiparous beef cows on day 3 of the estrous cycle

Endometrial-derived uterine histotroph is a critical component of nutrient supply to a growing conceptus throughout gestation; however, the effect of nutritional plane on histotroph nutrient composition remains unknown in multiparous cows. We hypothesized that differing planes of nutrition would alter histotroph and serum nutrient composition in beef cattle. Thus, we evaluated serum and histotroph amino acid and glucose composition, and serum non-esterified fatty acids (NEFA) and blood urea nitrogen (BUN) in cows individually fed to maintain body weight (BW; 0 kd/d, n = 9; CON) compared with those losing moderate BW (-0.7 kg/d, n = 9; NEG). After 49 d of differing nutritional planes, cows were subjected to the 7-d CoSynch + controlled internal drug release device estrus synchronization protocol and then slaughtered on day 62. Blood serum (days 0 and 62) and uterine histotroph [day 62; from uterine horns ipsilateral and contralateral to the corpus luteum (CL)] were collected and analyzed for concentrations of amino acids, glucose, and NEFA. Performance characteristics, body composition via ultrasound (days 0 and 62), and carcass characteristics were collected. Body condition score, change in BW, average daily gain, dry matter intake, and gain:feed were decreased (P ≤ 0.05) in NEG vs. CON cows. There were no differences in body composition or carcass characteristics, except an increase (P ≤ 0.05) in dressing percentage in NEG cows due to differences in gut fill, consistent with study design. Serum NEFA increased (P ≤ 0.05) in the NEG group, but there were no differences between NEG vs. CON in glucose or BUN. Serum histidine increased (P ≤ 0.05) and alanine, isoleucine, and tryptophan decreased (P ≤ 0.05) in NEG vs. CON cows. Compared with that of the uterine horn ipsilateral to the CL, histotroph from the uterine horn contralateral to the CL had increased (P ≤ 0.05) isoleucine, asparagine, and proline concentrations in NEG cows, and decreased (P ≤ 0.05) tryptophan as a proportion of essential and total amino acids. There were no differences in glucose concentrations of histotroph contralateral or ipsilateral to the CL. Cow nutritional plane does alter serum and histotroph amino acid composition, although the presence of an embryo may be necessary to fully elucidate these changes. Differences in serum and histotroph tryptophan should be given consideration in future studies due to its importance as an essential amino acid in protein synthesis and bioactive affects.

Melatonin in Health and Disease: A Perspective for Livestock Production

Mounting evidence in the literature indicates an important role of endogenous and exogenous melatonin in driving physiological and molecular adaptations in livestock. Melatonin has been extensively studied in seasonally polyestrous animals whereby supplementation studies have been used to adjust circannual rhythms in herds of animals under abnormal photoperiodic conditions. Livestock undergo multiple metabolic and physiological adaptation processes throughout their production cycle which can result in decreased immune response leading to chronic illness, weight loss, or decreased production efficiency; however, melatonin’s antioxidant capacity and immunostimulatory properties could alleviate these effects. The cardiovascular system responds to melatonin and depending on receptor type and localization, melatonin can vasodilate or vasoconstrict several systemic arteries, thereby controlling whole animal nutrient partitioning via vascular resistance. Increased incidences of non-communicable diseases in populations exposed to circadian disruption have uncovered novel pathways of neurohormones, such as melatonin, influence health, and disease. Perturbations in immune function can negatively impact the growth and development of livestock which has been examined following melatonin supplementation. Specifically, melatonin can influence nutrient uptake, circulating nutrient profiles, and endocrine profiles controlling economically important livestock growth and development. This review focuses on the physiological, cellular, and molecular implications of melatonin on the health and disease of domesticated food animals.

Timing of maternal nutrient restriction during mid- to late-gestation influences net umbilical uptake of glucose and amino acids in adolescent sheep

Previous research demonstrated that maternal nutrient restriction during mid- to late-gestation influenced net umbilical uptakes of glucose and amino acids in sheep. However, it is unclear how the timing and duration of nutrient restriction during mid- to late-gestation influences net uterine, uteroplacental, and fetal flux of glucose and amino acids. On day 50 of gestation, 41 adolescent ewe lambs carrying singletons were randomly assigned to one of six dietary treatments: 1) 100% of nutrient requirements from days 50 to 90 of gestation (CON; n = 7); 2) 60% of nutrient requirements (RES; n = 7) from days 50 to 90 of gestation; 3) 100% of nutrient requirements from days 50 to 130 of gestation (CON-CON; n = 6); 4) 100% of nutrient requirements from days 50 to 90 of gestation and 60% of nutrient requirements from days 90 to 130 of gestation (CON-RES; n = 7); 5) 60% of nutrient requirements from days 50 to 90 of gestation and 100% of nutrient requirements from days 90 to 130 of gestation (RES-CON; n = 7); or 6) 60% of nutrient requirements from days 50 to 130 of gestation (RES-RES; n = 7). On day 90 (n = 14) and day 130 (n = 27), intraoperative procedures were performed to evaluate uteroplacental blood flows, collect blood samples, and then ewes were euthanized. Net uterine, uteroplacental, and umbilical fluxes of glucose and amino acids were calculated by multiplying blood flow by the arterial-venous concentration difference. Data from days 90 and 130 were analyzed separately using ANOVA in SAS. Maternal nutrient restriction during mid-gestation increased (P = 0.04) net umbilical glucose uptake but, maternal nutrient restriction during late-gestation decreased (P = 0.02) net umbilical glucose uptake. Net umbilical essential amino acid uptake decreased (P = 0.03) with nutrient restriction during mid-gestation; however, net umbilical uptakes of Phe (P = 0.02), Thr (P = 0.05), Met (P = 0.09), and His (P = 0.08) increased or tended to increase after nutrient restriction during late-gestation. These data demonstrate that net umbilical glucose and amino acid uptakes were influenced by the timing of nutrient restriction during mid- to late-gestation. Elevated net umbilical glucose uptake after mid-gestational nutrient restriction was sustained throughout late-gestation, independent of late-gestational feeding level. Long-term adaptations in umbilical glucose uptake may have implications for prenatal and postnatal growth and development of the offspring.

Melatonin Supplementation Alters Maternal and Fetal Amino Acid Concentrations and Placental Nutrient Transporters in a Nutrient Restriction Bovine Model

Melatonin rescues uterine blood flow and fetal body weight in a seasonal dependent manner within a nutrient restriction bovine model. We sought to identify the effects of nutrient restriction, melatonin, and sampling time on maternal and fetal amino acids, and placental nutrient transporters. Pregnant heifers received adequate or restricted nutrition, and 20 mg of melatonin or placebo from gestational days 160-240 over two seasons. On day 240 maternal and fetal blood, amnion, and placentomes were collected. Amino acid concentrations were determined by gas chromatography-mass spectrometry. Caruncle and cotyledon tissues were assessed for nutrient transporter density by qPCR. Data were analyzed using the MIXED procedure of SAS for fixed effects. In fall, melatonin rescued effects of nutrient restriction on System N, Anion, and total maternal amino acids. Furthermore, melatonin rescued effects of nutrient restriction on Systems A, N, Br, Bo, and essential amnion amino acids. In summer, melatonin rescued effects of nutrient restriction in Systems Br and Bo maternal amino acids. Furthermore, melatonin rescued effects of nutrient restriction on caruncle SLC38A10 and SLC38A2. Melatonin rescued effects of nutrient restriction in a seasonal dependent manner. These data align with previous studies suggesting melatonin is a more effective therapeutic in summer months.

Influence of hempseed cake inclusion on growth performance, carcass characteristics, feeding behavior, and blood parameters in finishing heifers

As the hemp industry continues to develop in the United States, there is an increasing interest in feeding byproducts of industrial hemp production to livestock. A completely randomized design experiment using crossbred finishing heifers (initial body weight [BW] ± SE = 494 ± 10 kg) was conducted to determine the effects of feeding hempseed cake in a corn-based finishing diet (10% forage) formulated to meet or exceed ruminally degradable and metabolizable protein requirements on growth performance, carcass characteristics, feeding behavior, and plasma parameters. Dietary treatments were the inclusion of 20% (dry matter [DM] basis) of dried corn distillers grains plus solubles (DDGS, n = 16) or hempseed cake (HEMP, n = 15). Cattle were housed in two pens, had ad libitum access to feed and water, and individual intakes and feeding behavior were monitored using the Insentec feeding system. Cattle were fed treatment diets for 111 d, and every 14 d BW were measured and blood samples were collected. Blood plasma was analyzed for glucose, urea nitrogen, and individual amino acids, and results were analyzed using repeated-measures analysis in SAS. Final BW, average daily gain, gain:feed, and hot carcass weight decreased (P ≤ 0.05) by 2.3%, 7.7%, 7.7%, and 2.6%, respectively, in heifers fed the HEMP diet than in heifers fed the DDGS diet. Net energy for maintenance and gain (Mcal/kg of feed, DM basis), estimated based on heifer intake and performance, were greater (P = 0.02) for the DDGS diet than for the HEMP diet. All other performance and carcass characteristics were not different (P ≥ 0.20) between treatments. Heifers fed the HEMP diet had greater (P < 0.05) plasma urea nitrogen concentration in samples from each collection day compared with heifers fed the DDGS diet, although there was a treatment-by-day interaction (P < 0.01) because of variability in the magnitude of treatment differences over time. Plasma glucose concentration was not influenced (P = 0.17) by dietary treatment. Plasma concentrations of total amino acids, nonessential amino acids, and essential amino acids were not different between treatments (P ≥ 0.09), although there were several interactions between treatment and day (P ≤ 0.04) for individual amino acids. These data suggest that hempseed cake has a lower net energy for maintenance and gain relative to DDGS when adequate metabolizable protein is supplied, while still providing adequate nutrition to support the acceptable performance of finishing cattle.

Effects of Antioxidant Intake on Fetal Development and Maternal/Neonatal Health during Pregnancy

During pregnancy, cycles of hypoxia and oxidative stress play a key role in the proper development of the fetus. Hypoxia during the first weeks is crucial for placental development, while the increase in oxygen due to the influx of maternal blood stimulates endothelial growth and angiogenesis. However, an imbalance in the number of oxidative molecules due to endogenous or exogenous factors can overwhelm defense systems and lead to excessive production of reactive oxygen species (ROS). Many pregnancy complications, generated by systemic inflammation and placental vasoconstriction, such as preeclampsia (PE), fetal growth restriction (FGR) and preterm birth (PTB), are related to this increase of ROS. Antioxidants may be a promising tool in this population. However, clinical evidence on their use, especially those of natural origin, is scarce and controversial. Following PRISMA methodology, the current review addresses the use of natural antioxidants, such as epigallocatechin gallate (EGCG), melatonin and resveratrol (RESV), as well as other classical antioxidants (vitamin C and E) during the prenatal period as treatment of the above-mentioned complications. We review the effect of antioxidant supplementation on breast milk in lactating mothers.

Effects of Supplemental Leucine on Growth, Nutrient Use, and Muscle and Visceral Tissue Mass in Holstein Bull Calves Fed Milk Replacer

To determine the effects of leucine supplementation on body weight (BW), tissue mass, nutrient digestibility, the concentration of serum amino acids (AAs) and metabolites, and protein abundance of elongation initiation factor 4E (eIF4E) in skeletal muscle, 23 Holstein bull calves (43. 3 ± 1.16 kg; 11.3 ± 0.57 days of age) fed milk replacer at 2.5% of body weight (BW; dry matter basis) were used in a randomized complete block design. Leucine was supplemented at 0, 0.4, 0.6, or 0.8 g Leu/kg BW per day for 28 d. Data were analyzed using the MIXED procedure of SAS. Leucine supplementation did not affect calf BW (P = 0.73), and digestibility of nitrogen (P = 0.21), organic matter (P = 0.28), and dry matter (P = 0.28). Masses proportional to BW of the pancreas (P = 0.04), omasum (P &lt; 0.01), and spleen (P = 0.01) were quadratically affected by treatment where tissue mass decreased at 0.4 g Leu/kg BW and increased at 0.6 and 0.8 g Leu/kg BW. Semitendinosus mass proportional to BW tended (P = 0.07) to be quadratically affected, as tissue mass increased at 0.4 g Leu/kg BW, and decreased at 0.6 and 0.8 g Leu/kg BW. Serum Leu concentration increased linearly (P = 0.002; day × time × treatment) across days and after feedings with increased supplemental Leu. Increasing supplemental Leu linearly decreased serum Ala (P &lt; 0.01), Arg (P = 0.04), Ile (P = 0.02), Met (P &lt; 0.01), and Pro (P = 0.05) concentrations, and quadratically affected serum Glu (P = 0.04) and Lys (P = 0.03) concentrations where serum Glu and Lys concentrations were decreased at 0.4 g Leu/kg BW and increased at 0.6 and 0.8 g Leu/kg BW. There was no effect of treatment on protein abundance of eIF4E in semitendinosus or longissimus dorsi. These data indicate that supplemental Leu did not influence ADG and nitrogen retention in calves fed milk replacer. However, changes in serum AA concentrations and tissue masses proportional to BW suggest that supplementation of Leu at lower levels could increase the use of AA for non-visceral tissue growth.

Effects of Melatonin Supplementation during Pregnancy on Reproductive Performance, Maternal-Placental-Fetal Redox Status, and Placental Mitochondrial Function in a Sow Model

Melatonin (MT) is a bio-antioxidant that has been widely used to prevent pregnancy complications, such as pre-eclampsia and IUGR during gestation. This experiment evaluated the impacts of dietary MT supplementation during pregnancy on reproductive performance, maternal-placental-fetal redox status, placental inflammatory response, and mitochondrial function, and sought a possible underlying mechanism in the placenta. Sixteen fifth parity sows were divided into two groups and fed each day of the gestation period either a control diet or a diet that was the same but for 36 mg of MT. The results showed that dietary supplementation with MT increased placental weight, while the percentage of piglets born with weight < 900 g decreased. Meanwhile, serum and placental MT levels, maternal-placental-fetal redox status, and placental inflammatory response were increased by MT. In addition, dietary MT markedly increased the mRNA levels of nutrient transporters and antioxidant-related genes involved in the Nrf2/ARE pathway in the placenta. Furthermore, dietary MT significantly increased ATP and NAD+ levels, relative mtDNA content, and the protein expression of Sirt1 in the placenta. These results suggested that MT supplementation during gestation could improve maternal-placental-fetal redox status and reproductive performance by ameliorating placental antioxidant status, inflammatory response, and mitochondrial dysfunction.

Melatonin alters bovine uterine artery hemodynamics, vaginal temperatures, and fetal morphometrics during late gestational nutrient restriction in a season-dependent manner

The objectives were to examine melatonin-mediated changes in temporal uterine blood flow (UBF), vaginal temperatures (VTs), and fetal morphometrics in 54 commercial Brangus heifers (Fall, n = 29; Summer, n = 25) during compromised pregnancy. At day 160 of gestation, heifers were assigned to one of the four treatments consisting of adequately fed (ADQ-CON; 100% National Research Council [NRC]; n = 13), global nutrient restricted (RES-CON; 60% NRC; n =13), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL, n = 13; RES-MEL, n = 15). In the morning (0500 hours; AM) and afternoon (1300 hours; PM) of day 220 of gestation, UBF was determined via Doppler ultrasonography, while temperature data loggers attached to progesterone-free controlled internal drug releases were used to record VTs. At day 240 of gestation, heifers underwent cesarean sections for fetal removal and morphometrics determination. The UBF and VT data were analyzed using repeated measures of analysis of variance (ANOVA), while the morphometrics was analyzed using the MIXED procedure of SAS. Seasons were analyzed separately. In Fall, a nutrition by treatment interaction was observed, where the RES-CON heifers exhibited reduced total UBF compared with ADQ-CON (5.67 ± 0.68 vs. 7.97 ± 0.54 L/min; P = 0.039). In Summer, MEL heifers exhibited increased total UBF compared with the CON counterparts (8.16 ± 0.73 vs. 6.00 ± 0.70 L/min; P = 0.048). Moreover, there was a nutrition by treatment by time interaction in VT for Fall and Summer heifers (P ≤ 0.005). In Fall, all groups had decreased VT in the morning compared with the afternoon (P < 0.05). Whereas, in Summer, VT increased for ADQ-CON and RES-CON (P < 0.0001) from morning to afternoon, the ADQ-MEL and RES-MEL remained constant throughout the day (P = 0.648). Furthermore, the RES-MEL-PM exhibited decreased VT compared with ADQ-CON-PM (38.91 ± 0.09 vs. 39.26 ± 0.09 °C; P = 0.018). Lastly, in Fall, a main effect of nutrition was observed on fetal weights, where the RES dams had fetuses with decreased body weight when compared with ADQ (24.08 ± 0.62 vs. 26.57 ± 0.64 kg; P = 0.0087). In Summer, a nutrition by treatment interaction was observed on fetal weights where the RES-CON dams had fetuses with reduced weight when compared with ADQ-CON and RES-MEL (P < 0.05). In summary, nutrient restriction decreased UBF and melatonin supplementation increased UBF depending on the season. Additionally, melatonin appeared to decrease VT and rescue fetal weights when supplemented in the Summer.

Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs

High preweaning mortality rates continue to limit sheep production globally, constituting a major economic and welfare concern. Greater losses in twin lambs (≥30%) compared with singletons (≥10%) are attributed primarily to lower birth weight and increased risk of intrapartum hypoxia, leading to impairment of thermoregulation, neuromotor activity, and maternal bonding behavior. Previous intensive studies demonstrated that supplementing pregnant ewes with melatonin reduced the adverse effects of fetal growth restriction and perinatal hypoxia on the neonatal brain via increased umbilical blood flow, placental efficiency, and antioxidant actions. The current study examined the effects of supplementing pregnant ewes with melatonin on lamb survival, birth weight, and behavior under intensive conditions. From gestational day (gD) 80 until parturition, pregnant singleton and twin-bearing ewes were supplemented with melatonin via a 2-mg capsule fed daily (Mel-FED, n = 61) or 18 mg subcutaneous implant (Regulin), with one implant administered at gD80 and another at gD125 (Mel-IMP, n = 60). Control ewes received no supplementation (CTL, n = 60). Ewes and lambs were monitored via video throughout parturition. Postpartum measures were taken from lambs at 4 and 24 h (live weight [LW], rectal temperature, serum immunoglobulin G, and latency to stand and suck after birth) and LW at 72 h, 7 d, marking (49.7 ± 0.2 d), and weaning (124.2 ± 0.8 d). Chi-square analysis was used to compare lamb survival between treatment groups. There were no treatment effects on singleton lamb survival. Melatonin supplementation tended to increase the proportion of twin lambs surviving from birth to weaning (Mel-FED = 85.5%; Mel-IMP = 85.9%; CTL = 72.9%; each P < 0.1). Survival of first-born twins did not differ between treatment (each ~90%, P = 0.745) but within second-born twins, survival of Mel-FED was greater than CTL (81.6 vs. 57.1%, P = 0.023), and Mel-IMP (78.1%) tended to be greater than CTL (P = 0.068). Similarly, in second-born twins exposed to prolonged parturition (≥ 90 min), survival of lambs from Mel-FED ewes was greater than CTL (86.7% vs. 42.9%, P = 0.032), while Mel-IMP was intermediate (66.7%). These data suggest that the neuroprotective actions of melatonin may improve twin lamb survival by increasing tolerance of prolonged parturition and provide a sound basis for continued testing in extensively managed sheep flocks.

Effects of feeding bulls dried corn distiller's grains plus solubles or CaSO4 on mineral and metabolite concentrations in serum and seminal plasma

Yearling Angus bulls (n = 36) were assigned one of three diets: 1) 60 % concentrate as corn (CON, 0.2 % S, 13.4 % CP; n = 12); 2) 60 % dried corn distiller's grains plus solubles (60DDGS 0.5 % S, 22.0 % CP; n = 12); 3) CON diet + equivalent sulfur of 60DDGS as CaSO₄ (SULF, 0.5 % S, 13.9 % CP; n = 12) to evaluate effects of feeding 60 % DDGS or sulfur as CaSO₄ on mineral and metabolite concentrations in serum and seminal plasma. Treatment × day interactions (P < 0.03) were observed for serum Cu, Se, and Mo. For Cu at d 112, lesser (P < 0.01) concentrations were observed in bulls fed the 60DDGS compared to SULF and CON diets. There were greater (P < 0.01) concentrations of Se at d 112 in bulls fed 60DDGS than CON and SULF diets. Concentrations of Mo were greater at d 56 and 112 (P < 0.01) in bulls fed CON compared to SULF and 60DDGS diets. In seminal plasma, there were treatment × day interactions (P < 0.02) for Cu and Mo. For Cu, at d 112, there was a lesser (P < 0.01) concentration in the bulls fed SULF compared to CON and 60DDGS diets. For Mo, there was a greater (P < 0.01) concentration in bulls fed the CON than 60DDGS and SULF diets at d 56 and 112. Changes in mineral and metabolite concentrations may have effects on bull reproductive performance when there is a relatively greater dietary sulfur content.

Effects of nutrient restriction and melatonin supplementation from mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep

The objective of this experiment was to evaluate the effects of nutrient restriction and melatonin supplementation during mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep. Ewes were randomly assigned to one of 4 dietary treatments arranged in a 2 × 2 factorial design. Ewes were fed to provide 100% (adequate; ADQ) or 60% (restricted; RES) of nutrient recommendations, and diets were supplemented with either no melatonin (control; CON) or 5 mg melatonin/d (melatonin; MEL). This resulted in 4 treatment groups: CON-ADQ (n = 7), CON-RES (n = 8), MEL-ADQ (n = 8), MEL-RES (n = 8). Treatments began on day 50 of gestation, and ewes were euthanized on day 130 for tissue collection. The maternal and fetal small intestine were collected and assayed for small intestinal carbohydrase activities. Data were analyzed using the GLM procedure of SAS with fetal sex, melatonin, nutrition, and the melatonin by nutrition interaction included in the model statement. There were no melatonin by nutrition interactions for maternal or fetal small intestinal protein concentration or carbohydrase activities (P ≥ 0.11). Dietary melatonin supplementation decreased (P = 0.03) maternal small intestinal protein concentration by 22.7% and increased (P = 0.03) maternal small intestinal glucoamylase, isomaltase, and maltase activity per gram protein by 45.5%, 41.3%, and 40.6%, respectively. Nutrient restriction from mid-to-late gestation did not influence (P ≥ 0.46) maternal small intestinal protein concentration, or maltase, isomaltase, and lactase activity. Maternal glucoamylase activity per gram intestine increased (P = 0.05) with nutrient restriction by 49.1%. Melatonin supplementation and maternal nutrient restriction did not influence (P ≥ 0.15) fetal small intestinal protein concentration, or glucoamylase, isomaltase, and lactase activity. Maternal nutrient restriction from mid-to-late gestation decreased (P = 0.05) fetal maltase activity per gram intestine by 20.5% but did not influence fetal maltase activity per gram protein. These data indicate that some maternal and fetal carbohydrases are influenced by nutrient restriction and melatonin supplementation in sheep. More information is needed to understand how nutritional and hormonal factors regulate digestive enzyme activity in ruminants to design improved maternal nutrition programs to optimize fetal growth and development while maintaining maternal productivity.

Neonatal lamb mortality: major risk factors and the potential ameliorative role of melatonin

High incidences of pre-weaning mortality continue to limit global sheep production, constituting a major economic and welfare concern. Despite significant advances in genetics, nutrition, and management, the proportion of lamb deaths has remained stable at 15–20% over the past four decades. There is mounting evidence that melatonin can improve outcomes in compromised ovine pregnancies via enhanced uterine bloodflow and neonatal neuroprotection. This review provides an overview of the major risk factors and underlying mechanisms involved in perinatal lamb mortality and discusses the potential of melatonin treatment as a remedial strategy. Supplementing pregnant ewes with melatonin enhances uterine bloodflow and fetal oxygenation, and potentially birthweight and neonatal thermogenic capacity. Melatonin freely crosses the ovine placenta and blood-brain barrier and provides neuroprotection to the fetal lamb during periods of chronic and acute hypoxia throughout gestation, with improved behavioural outcomes in hypoxic neonates. The current literature provides strong evidence that maternal melatonin treatment improves outcomes for lambs which experience compromised in utero development or prolonged parturition, though to date this has not been investigated in livestock production systems. As such there is a clear basis for continued research into the effects of maternal melatonin supplementation during gestation on pre-weaning survival under extensive production conditions.

Effects of Nutrient Restriction During Midgestation to Late Gestation on Maternal and Fetal Postruminal Carbohydrase Activities in Sheep

To examine the effects of nutrient restriction during midgestation to late gestation on maternal and fetal digestive enzyme activities, 41 singleton ewes (48.3 ± 0.6 kg of BW) were randomly assigned to dietary treatments: 100% (control; CON; n = 20) or 60% of nutrient requirements (restricted; RES; n = 21) from day 50 until day 90 (midgestation). At day 90, 14 ewes (CON, n = 7; RES, n = 7) were euthanized. The remaining ewes were subjected to treatments of nutrient restriction or remained on a control diet from day 90 until day 130 (late gestation): CON-CON (n = 6), CON-RES (n = 7), RES-CON (n = 7), and RES-RES (n = 7) and were euthanized on day 130. The fetal and maternal pancreas and small intestines were weighed, subsampled, and assayed for digestive enzyme activity. One unit (U) of enzyme activity is equal to 1 µmol of product produced per minute for amylase, glucoamylase, lactase, and trypsin and 0.5 µmol of product produced per minute for maltase and isomaltase. Nutrient restriction during midgestation and late gestation decreased (P < 0.05) maternal pancreatic and small intestinal mass but did not affect fetal pancreatic or small intestinal mass. Maternal nutrient restriction during late gestation decreased (P = 0.03) fetal pancreatic trypsin content (U/pancreas) and tended to decrease (P < 0.08) fetal pancreatic trypsin concentration (U/g), specific activity (U/g protein), and content relative to BW (U/kg of BW). Nutrient restriction of gestating ewes decreased the total content of α-amylase (P = 0.04) and tended to decrease total content of trypsin (P = 0.06) and protein (P = 0.06) in the maternal pancreas on day 90. Nutrient restriction during midgestation on day 90 and during late gestation on day 130 decreased (P = 0.04) maternal pancreatic α-amylase-specific activity. Sucrase activity was undetected in the fetal and maternal small intestine. Nutrient restriction during late gestation increased (P = 0.01) maternal small intestinal maltase and lactase concentration and tended to increase (P = 0.06) isomaltase concentration. Realimentation during late gestation after nutrient restriction during midgestation increased lactase concentration (P = 0.04) and specific activity (P = 0.05) in the fetal small intestine. Fetal small intestinal maltase, isomaltase, and glucoamylase did not respond to maternal nutrient restriction. These data indicate that some maternal and fetal digestive enzyme activities may change in response to maternal nutrient restriction.

Melatonin Increases Fetal Weight in Wild-Type Mice but Not in Mouse Models of Fetal Growth Restriction

Fetal growth restriction (FGR) presents with an increased risk of stillbirth and childhood and adulthood morbidity. Melatonin, a neurohormone and antioxidant, has been suggested as having therapeutic benefit in FGR. We tested the hypothesis that melatonin would increase fetal growth in two mouse models of FGR which together represent a spectrum of the placental phenotypes in this complication: namely the endothelial nitric oxide synthase knockout mouse (eNOS^-/-) which presents with abnormal uteroplacental blood flow, and the placental specific Igf2 knockout mouse (P0^+/-) which demonstrates aberrant placental morphology akin to human FGR. Melatonin (5 μg/ml) was administered via drinking water from embryonic day (E)12.5 in C57Bl/6J wild-type (WT), eNOS^-/-, and P0^+/- mice. Melatonin supplementation significantly increased fetal weight in WT, but not eNOS^-/- or P0^+/- mice at E18.5. Melatonin did, however, significantly increase abdominal circumference in P0^+/- mice. Melatonin had no effect on placental weight in any group. Uterine arteries from eNOS^-/- mice demonstrated aberrant function compared with WT but melatonin treatment did not affect uterine artery vascular reactivity in either of these genotypes. Umbilical arteries from melatonin treated P0^+/- mice demonstrated increased relaxation in response to the nitric oxide donor SNP compared with control. The increased fetal weight in WT mice and abdominal circumference in P0^+/-, together with the lack of any effect in eNOS^-/-, suggest that the presence of eNOS is required for the growth promoting effects of melatonin. This study supports further work on the possibility of melatonin as a treatment for FGR.

Effects of body condition score (BCS) on steroid- and eicosanoid-metabolizing enzyme activity in various mare tissues during winter anoestrus

The objective of this study was to determine the activity of steroid- and eicosanoid-metabolizing enzymes in horses with varying BCSs. The BCSs of twenty non-pregnant, anoestrous mares were determined prior to euthanasia, and tissue samples were collected from the liver, kidney, adrenal gland, ovary and endometrium. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A) and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined using luminogenic substrates. The MIXED procedure of SAS was used to test the effect of BCS on enzyme activity and differences between tissues. Activity of CYP1A in adrenals was increased (p ≤ .05) in BCS 5 versus BCSs 4 and 6. Activity of CYP1A in the liver was increased (p = .05) in BCS 4 versus BCSs 5 and 6. Activity of CYP1A was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and kidney. Activity of CYP2C was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and endometrium. Activity of CYP3A was only detectable in the liver. Activity of UGT in the kidney was decreased (p = .02) in BCS 4 versus BCSs 5 and 6. Activity of UGT was threefold greater (p < .0001) in the liver than in the kidney, whereas activity of UGT was ninefold greater (p < .0001) in the kidney than in the ovary and endometrium. In general, BCS did not alter the activity of steroid- and eicosanoid-metabolizing enzymes in horses. However, tissue differences in these enzymes indicated abundant hepatic metabolism in horses, which is similar to other livestock species.

Effects of excess metabolizable protein on ovarian function and circulating amino acids of beef cows: 1. Excessive supply from corn gluten meal or soybean meal

In the dairy industry, excess dietary CP is consistently correlated with decreased conception rates. However, the source from which excess CP is derived and how it affects reproductive function in beef cattle is largely undefined. The objective of this experiment was to determine the effects of feeding excess metabolizable protein (MP) from feedstuffs differing in rumen degradability on ovulatory follicular dynamics, subsequent corpus luteum (CL) development, steroid hormone production and circulating amino acids (AA) in beef cows. Non-pregnant, non-lactating mature beef cows (n=18) were assigned to 1 of 2 isonitrogenous diets (150% of MP requirements) designed to maintain similar BW and body condition score (BCS) between treatments. Diets consisted of ad libitum corn stalks supplemented with corn gluten meal (moderate rumen undegradable protein (RUP); CGM) or soybean meal (low RUP; SBM). After a 20-day supplement adaptation period, cows were synchronized for ovulation. After 10 days of synchronization, gonadotropin releasing hormone (GnRH) was administered to reset ovarian follicular growth. Starting at GnRH administration and daily thereafter until spontaneous ovulation, transrectal ultrasonography was used to diagram ovarian follicular growth, and blood samples were collected for hormone, metabolite and AA analyses. After 7 days of visual detection of estrus, CL size was determined via ultrasound. Data were analyzed using the MIXED procedures of SAS. As designed, cow BW and BCS were not different (P⩾0.33). Ovulatory follicular wavelength, antral follicle count, ovulatory follicle size at dominance and duration of dominance were not different (P>0.13) between treatments. Cows supplemented with CGM had greater post-dominance ovulatory follicle growth, larger dominant follicles at spontaneous luteolysis, shorter proestrus, and larger ovulatory follicles (P⩽0.03) than SBM cows. No differences (P⩾0.44) in peak estradiol, ratio of estradiol to ovulatory follicle volume, or plasma urea nitrogen were observed. While CL volume and the ratio of progesterone to CL volume were not affected by treatment (P⩾0.24), CGM treated cows tended to have decreased (P=0.07) circulating progesterone 7 days post-estrus compared with SBM cows. Although total circulating plasma AA concentration did not differ (P=0.70) between treatments, CGM cows had greater phenylalanine (P=0.03) and tended to have greater leucine concentrations (P=0.07) than SBM cows. In summary, these data illustrate that excess MP when supplemented to cows consuming a low quality forage may differentially impact ovarian function depending on ruminal degradability of the protein source.

Effects of excess metabolizable protein on ovarian function and circulating amino acids of beef cows: 2. Excessive supply in varying concentrations from corn gluten meal

In the dairy industry, excess dietary CP is consistently correlated with decreased conception rates. However, amount of excess CP effects on reproductive function in beef cattle is largely undefined. The objective of this experiment was to determine the effects of excess metabolizable protein (MP) supplementation from a moderately abundant rumen undegradable protein (RUP) source (corn gluten meal: 62% RUP) on ovarian function and circulating amino acid (AA) concentrations in beef cows consuming low quality forage. Non-pregnant, non-lactating beef cows (n=16) were allocated by age, BW and body condition score (BCS) to 1 of 2 isocaloric supplements designed to maintain BW for 60 days. Cows had ad libitum access to corn stalks and were individually offered a corn gluten meal-based supplement daily at 125% (MP125) or 150% (MP150) of National Research Council (NRC) MP requirements. After a 20-day supplement adaptation period, cows were synchronized for ovulation. After 10 days of synchronization, follicular growth was reset with gonadotropin releasing hormone. Daily thereafter, transrectal ultrasonography was performed to diagram ovarian follicular waves, and blood samples were collected for hormone, metabolite and AA analyses. After 7 days of observation of estrus, corpus luteum (CL) size was determined via ultrasound. Data were analyzed using the MIXED procedures of SAS. No differences (P⩾0.21) in BW and BCS existed throughout the study; however, plasma urea N at ovulation was greater (P=0.04) in MP150. Preovulatory ovarian follicle size at dominance, duration of dominance, size at spontaneous luteolysis, length of proestrus and wavelength were not different (P⩾0.11) between treatments. However, ovulatory follicles were larger (P=0.04) and average antral follicle count was greater (P=0.01) in MP150 than MP125. Estradiol concentration and ratio of estradiol to ovulatory follicle volume were not different due to treatment (P⩾0.25). While CL volume 7 days post-estrus was greater (P<0.01) in MP150 than MP125, circulating progesterone 7 days post-estrus and ratio of progesterone to CL volume were not different (P⩾0.21). Total AA were not different (P⩾0.76) at study initiation or completion; however, as a percent of total AA, branched-chain AA at ovulation were greater (P=0.02) in MP150. In conclusion, supplementation of CP at 150% of NRC MP requirements from a moderately undegradable protein source may enhance growth of the ovulatory follicle and subsequent CL compared with MP supplementation at 125% of NRC MP requirements.

Melatonin rescues cardiovascular dysfunction during hypoxic development in the chick embryo

There is a search for rescue therapy against fetal origins of cardiovascular disease in pregnancy complicated by chronic fetal hypoxia, particularly following clinical diagnosis of fetal growth restriction (FGR). Melatonin protects the placenta in adverse pregnancy; however, whether melatonin protects the fetal heart and vasculature in hypoxic pregnancy independent of effects on the placenta is unknown. Whether melatonin can rescue fetal cardiovascular dysfunction when treatment commences following FGR diagnosis is also unknown. We isolated the effects of melatonin on the developing cardiovascular system of the chick embryo during hypoxic incubation. We tested the hypothesis that melatonin directly protects the fetal cardiovascular system in adverse development and that it can rescue dysfunction following FGR diagnosis. Chick embryos were incubated under normoxia or hypoxia (14% O2) from day 1 ± melatonin treatment (1 mg/kg/day) from day 13 of incubation (term ~21 days). Melatonin in hypoxic chick embryos rescued cardiac systolic dysfunction, impaired cardiac contractility and relaxability, increased cardiac sympathetic dominance, and endothelial dysfunction in peripheral circulations. The mechanisms involved included reduced oxidative stress, enhanced antioxidant capacity and restored vascular endothelial growth factor expression, and NO bioavailability. Melatonin treatment of the chick embryo starting at day 13 of incubation, equivalent to ca. 25 wk of gestation in human pregnancy, rescues early origins of cardiovascular dysfunction during hypoxic development. Melatonin may be a suitable antioxidant candidate for translation to human therapy to protect the fetal cardiovascular system in adverse pregnancy.

Impacts of Maternal Nutrition on Vascularity of Nutrient Transferring Tissues during Gestation and Lactation

As the demand for food increases with exponential growth in the world population, it is imperative that we understand how to make livestock production as efficient as possible in the face of decreasing available natural resources. Moreover, it is important that livestock are able to meet their metabolic demands and supply adequate nutrition to developing offspring both during pregnancy and lactation. Specific nutrient supplementation programs that are designed to offset deficiencies, enhance efficiency, and improve nutrient supply during pregnancy can alter tissue vascular responses, fetal growth, and postnatal offspring outcomes. This review outlines how vascularity in nutrient transferring tissues, namely the maternal gastrointestinal tract, the utero-placental tissue, and the mammary gland, respond to differing nutritional planes and other specific nutrient supplementation regimes.

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.

Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development

This paper identifies a common nutritional pathway relating maternal through to fetal protein-energy malnutrition (PEM) and compromised fetal kidney development. Thirty-one twin-bearing sheep were fed either a control (n=15) or low-protein diet (n=16, 17 vs. 8.7 g crude protein/MJ metabolizable energy) from d 0 to 65 gestation (term, ∼145 d). Effects on the maternal and fetal nutritional environment were characterized by sampling blood and amniotic fluid. Kidney development was characterized by histology, immunohistochemistry, vascular corrosion casts, and molecular biology. PEM had little measureable effect on maternal and fetal macronutrient balance (glucose, total protein, total amino acids, and lactate were unaffected) or on fetal growth. PEM decreased maternal and fetal urea concentration, which blunted fetal ornithine availability and affected fetal hepatic polyamine production. For the first time in a large animal model, we associated these nutritional effects with reduced micro- but not macrovascular development in the fetal kidney. Maternal PEM specifically impacts the fetal ornithine cycle, affecting cellular polyamine metabolism and microvascular development of the fetal kidney, effects that likely underpin programming of kidney development and function by a maternal low protein diet.—Dunford, L. J., Sinclair, K. D., Kwong, W. Y., Sturrock, C., Clifford, B. L., Giles, T. C., Gardner, D. S.. Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development.