Stage-specific nutritional management and developmental programming to optimize meat production

Over the past few decades, genetic selection and refined nutritional management have extensively been used to increase the growth rate and lean meat production of livestock. However, the rapid growth rates of modern breeds are often accompanied by a reduction in intramuscular fat deposition and increased occurrences of muscle abnormalities, impairing meat quality and processing functionality. Early stages of animal development set the long-term growth trajectory of offspring. However, due to the seasonal reproductive cycles of ruminant livestock, gestational nutrient deficiencies caused by seasonal variations, frequent droughts, and unfavorable geological locations negatively affect fetal development and their subsequent production efficiency and meat quality. Therefore, enrolling livestock in nutritional intervention strategies during gestation is effective for improving the body composition and meat quality of the offspring at harvest. These crucial early developmental stages include embryonic, fetal, and postnatal stages, which have stage-specific effects on subsequent offspring development, body composition, and meat quality. This review summarizes contemporary research in the embryonic, fetal, and neonatal development, and the impacts of maternal nutrition on the early development and programming effects on the long-term growth performance of livestock. Understanding the developmental and metabolic characteristics of skeletal muscle, adipose, and fibrotic tissues will facilitate the development of stage-specific nutritional management strategies to optimize production efficiency and meat quality.

Impact of Maternal Feed Restriction at Different Stages of Gestation on the Proteomic Profile of the Newborn Skeletal Muscle

We aimed to investigate the effects of the maternal plane of nutrition during gestation on the proteome profile of the skeletal muscle of the newborn. Pregnant goats were assigned to the following experimental treatments: restriction maintenance (RM) where pregnant dams were fed at 50% of their maintenance requirements from 8−84 days of gestation, and then feed of 100% of the maintenance requirements was supplied from 85—parturition (n = 6); maintenance restriction (MR) where pregnant dams were fed at 100% of their maintenance requirements from 8−84 days of gestation, and then experienced feed restriction of 50% of the maintenance requirements from 85—parturition (n = 8). At birth, newborns were euthanized and samples of the Longissimus dorsi muscle were collected and used to perform HPLC-MS/MS analysis. The network analyses were performed to identify the biological processes and KEGG pathways of the proteins identified as differentially abundant protein and were deemed significant when the adjusted p-value (FDR) < 0.05. Our results suggest that treatment RM affects the energy metabolism of newborns’ skeletal muscle by changing the energy-investment phase of glycolysis, in addition to utilizing glycogen as a carbon source. Moreover, the RM plane of nutrition may contribute to fatty acid oxidation and increases in the cytosolic α-KG and mitochondrial NADH levels in the skeletal muscle of the newborn. On the other hand, treatment MR likely affects the energy-generation phase of glycolysis, contributing to the accumulation of mitochondrial α-KG and the biosynthesis of glutamine.

Maternal intake restriction programs the energy metabolism, clock circadian regulator and mTOR signals in the skeletal muscles of goat offspring probably via the protein kinase A-cAMP-responsive element-binding proteins pathway

The biological mechanism by which maternal undernutrition increases the metabolic disorder risk of skeletal muscles in offspring is not fully understood. We hypothesize that maternal intake restriction influences metabolic signals in the skeletal muscles of offspring via a glucagon-mediated pathway. Twenty-four pregnant goats were assigned to the control group (100% of the nutrients requirement, n = 12) and restricted group (60% of the control feed allowance from pregnant days 45 to 100, n = 12). Blood and L ongissimus thoracis muscle were sampled from dams (100 d of gestation), fetuses (100 d of gestation), and kids (90 d after birth) in each group. The data were analyzed using the linear MIXED model, with the multiple comparison method of SIDAK applied. Intake restriction reduced (P < 0.05) the total blood protein of dams and fetuses. Maternal restriction decreased (P < 0.05) the cAMP-responsive element-binding protein 1 (CREB1), CREB-binding protein (CREBBP), protein kinase A (PKA), aryl hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1), protein kinase B (AKT1), mammalian target of rapamycin (mTOR), and regulatory-associated protein of mTOR (RPTOR) mRNA expression in the fetuses, and reduced (P < 0.05) the CREBBP, nuclear receptor subfamily 1 group H member 3 (NR1H3), D-box binding PAR bZIP transcription factor (DBP) and PKA mRNA levels in the kids, but increased (P < 0.05) the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1 A) and tuberous sclerosis 2 (TSC2) mRNA levels in the fetuses. The mRNA expression of clock circadian regulator (CLOCK) and TSC2 genes was increased (P < 0.05) in the restricted kids. The protein expression of total PKA and phosphorylated PKA in the restricted fetuses and kids were downregulated (P < 0.05), and the protein expression of total mTOR and phosphorylated mTOR were reduced (P < 0.05) in the restricted fetuses and kids. Maternal intake restriction regulated fat oxidation, protein synthesis, and circadian clock expression in the muscles of the offspring probably via the glucagon-mediated PKA-CREB pathway, which reveals a noteworthy molecular pathway that maternal undernutrition leads to metabolic adaptation of skeletal muscle in offspring.

Mid- to late- gestational maternal nutrient restriction followed by realimentation alters development and lipid composition of liver and skeletal muscles in ovine fetuses

Maternal nutrient restriction during gestation adversely affects offspring growth and development of liver and skeletal muscle tissues. Realimentation following nutrient restriction may alleviate these negative impacts on development but may alter metabolism and tissue composition. Forty-eight ewes, pregnant with singletons, were fed to meet 100% National Research Council (NRC) recommendations starting at the beginning of gestation. On d 50 of gestation, 7 ewes were euthanized (BASE), and fetal liver, skeletal muscles, and blood samples were collected. The remaining animals were fed either 100% of NRC recommendations (CON) or 60% NRC recommendations (RES), a subset were euthanized at d 90 of gestation (n = 7/treatment), and fetal samples were collected. Remaining ewes were maintained on the current diet (CON-CON, n = 6; RES-RES, n = 7) or switched to the alternate diet (CON-RES, RES-CON; n = 7/treatment). On d 130 of gestation, the remaining ewes were euthanized, and fetal samples were collected. At d 130 of gestation, maternal nutrient restriction during late-gestation (RES-RES and CON-RES) decreased fetal liver weight (P < 0.01) and cross-sectional area in triceps brachii (P = 0.01; TB), longissimus dorsi (P = 0.02; LM), and semitendinosus (P = 0.05; STN) muscles. Maternal nutrient restriction during mid-gestation increased hepatocyte vacuole size at d 130 of gestation. Late-gestational maternal nutrient restriction increased mRNA expression of insulin-like growth factor (IGF) binding protein-1 (P < 0.01), glycogen synthase 2 (P = 0.01; GYS2), and pyruvate dehydrogenase kinase 1 (P < 0.01; PDHK1) in the liver and IGF receptor 1 (P = 0.05) in the LM. Lipid concentration in the LM was decreased by late-gestational nutrient restriction (P = 0.01) and increased by mid-gestational nutrient restriction in STN (P = 0.03) and TB (P < 0.01). Principal component analysis of lipidomics data demonstrated clustering of principal components by day of gestation and elastic net regression identified 50, 44, and 29 lipids that classified the treatments in the fetal liver, LM, and blood, respectively. In conclusion, restricting maternal nutrition impacts fetal liver and muscle morphology, gene expression, and lipid metabolism, whereas realimentation attenuated some of these effects. Therefore, realimentation may be a viable strategy to reduce the impacts of nutrient restriction, but can lead to alterations in lipid metabolism in sheep.

Effect of maternal overnutrition on predisposition to insulin resistance in the foal: Foal skeletal muscle development and insulin signaling

Skeletal muscle plays an integral role in the ability of a horse to perform at high levels. Shifts in skeletal muscle development in response to maternal plane of nutrition may have substantial and lasting impacts on athletic performance and whole-body metabolism. Therefore, sixteen Quarter Horse mares were used in a completely randomized design and maintained at a body condition score (BCS) 6 until start of third trimester. On d 235 of gestation, mares were randomly assigned to receive one of two dietary treatments with a diet formulated to meet requirements during late gestation (CON; n = 8), and an overfed diet (HIGH; n = 8) where mares received an additional 40% above CON. Five h after parturition, foals were euthanized, and gluteus medius, triceps brachii, and semitendinosus were harvested for analyses. Gene expression was determined by qPCR and western immunoblotting was used to quantify total and phosphorylated forms of proteins involved in skeletal muscle metabolism with tubulin as the loading control. All data were analyzed using PROC MIXED of SAS. Foals from HIGH mares exhibited larger skeletal muscle fibers by area (P <0.05), and a shift in muscle fiber development towards type I slow twitch muscle fibers (P <0.05). Relative expression of glucose transporter 4 (GLUT4) was lower in HIGH foals compared to CON in gluteus medius (P = 0.05). Insulin receptor isoform B (INSR-B) and insulin-like growth factor 1 receptor (IGF1R) were greater in triceps brachii of HIGH foals compared to CON (P ≤ 0.03). Insulin receptor isoform A (INSR-A), however, tended to be lower in triceps brachii of HIGH compared to CON (P = 0.10). Ratios of phosphorylated to total extracellular signal-regulated protein kinase 1/2 (ERK1/2) and c-June N-terminal kinase (JNK) were higher in HIGH foals compared to CON (P ≤0.04) in gluteus medius. There were no differences observed for phosphorylated to total protein ratios in semitendinosus and triceps brachii muscles; however, total ERK1/2 tended to be elevated (P <0.10) in semitendinosus from CON foals compared to HIGH. There was no difference in phosphorylated or total protein kinase B (AKT) (P >0.14). These data indicate hypertrophy of skeletal muscle fibers and a shift towards type I slow twitch fibers in HIGH foals. Furthermore, this study identifies muscle specific changes in gene expression and downstream insulin receptor signaling, which may contribute to future metabolic abnormalities in response to maternal overnutrition.

Maternal Nutrition and Developmental Programming of Male Progeny

Simple Summary

The objective of the following review is to describe available literature on the interaction between maternal nutrition and developmental programming in male offspring. The majority of current research focuses on female offspring or fails to take offspring sex into account, though sexual dimorphisms in response to maternal diet are well-recognized. This leaves a large gap in the understanding of male developmental programming. This review will specifically discuss the impacts of maternal dietary energy and protein on bull and ram growth, development, and reproductive capacity in later life.

Abstract

Poor maternal nutrition can cause several maladaptive phenotypes in exposed offspring. While non-sex-specific and female-specific adaptations are well-documented, male-specific outcomes are still poorly understood. Of particular interest are the outcomes in bulls and rams, as developmental programming directly impacts long-term productivity of the animal as well as human food security. The following review discusses the impact of poor maternal dietary energy and protein on bull and ram developmental programming as it relates to growth, development, and reproductive capacity. The review also highlights the importance of the timing of maternal dietary insult, as early-, mid-, and late-gestational insults can all have varying effects on offspring.

Effects of mid-gestational l-citrulline supplementation to twin-bearing ewes on umbilical blood flow, placental development, and lamb production traits

The objective of the study was to examine how l-citrulline supplementation to ewes during mid-gestation influences placental activity, placental blood flow, lamb body weight, and carcass characteristics. Two studies were completed. A pharmacokinetic study to compare circulating plasma amino acid concentrations after a single intravenous injection of 155 µmol/kg BW l-citrulline or after an isonitrogenous amount of l-alanine (control; 465 µmol/kg BW). Increases (P < 0.05) in circulating citrulline concentrations were detected for 8 h after l-citrulline injection versus the control. Similarly, increases (P < 0.05) in circulating arginine concentrations were detected for 24 h after l-citrulline treatment. The second study used 12 ewes with twin pregnancies. Daily intravenous injections of either l-citrulline or l-alanine were administered for 39 d from d 42–45 to 81–84 of gestation. Ewes were limit-fed at 85% daily energy requirements during the injection period. A decrease (P < 0.0001) in body weight was observed in both treatment groups during this period. No treatment differences were observed in circulating pregnancy-specific protein B concentrations or placental blood flow during the treatment and post-treatment gestational period. No treatment differences were observed in lamb survival nor in lamb birth, weaning and slaughter weights. Treatment did not influence lamb carcass composition or organ weights. However, there was a tendency (P = 0.10) for an increase in antral follicle numbers in ovaries from ewe lambs derived from ewes treated with l-citrulline. In summary, a daily l-citrulline injection increased both circulating citrulline and arginine concentrations in ewes, but daily l-citrulline injections during mid-gestation did not produce any detectable changes in placental activity and blood flow, neonatal and postnatal lamb development, and lamb carcass composition at slaughter. In conclusion, no benefits in placental function and lamb development were observed after providing l-citrulline during mid-gestation in ewes exposed to a mild energy restriction, but there was an indication that follicle numbers in ewe lambs were positively influenced by l-citrulline treatment during fetal development.

Ante-Natal and Post-Natal Influences on Neonatal Immunity, Growth and Puberty of Calves-A Review

Simple Summary

The objective of this review is to give the reader an overview of interactions between immunity, growth and puberty in calves and highlight how these influence future performances. The risk of morbidity and mortality is high during the first four weeks of age. Adaption to extra-uterine life starts early during embryonic development and is underpinned by optimal maternal nutrition. It is known that colostrum is paramount to neonate nutrition and passive immunity. Good colostrum management allows the calf to develop coping mechanisms to efficiently utilize feed resources for optimal growth. A deeper understanding of these interactions paves the way for developing strategies to improve immune responses to environmental pathogens, optimal growth and timely attainment of puberty in calves. The literature reviewed here shows that there are opportunities to enhance future performance of cattle paying attention to the interaction of nutrition and immunity at early developmental stages. This then guarantees efficient neonate nutrition and profitable cattle production.

Abstract

Calf immunity, growth and puberty are important factors affecting heifer productivity. The first four weeks of age are critical for reducing calf morbidity and mortality. It is well documented that colostrum is paramount to neonatal nutrition and passive immunity, however, adaptation to extra-uterine life starts early during embryonic development. Therefore, successful calf rearing strategies are underpinned by adequate maternal nutrition during gestation, and good colostrum management. A deeper understanding of these interactions paves the way for developing strategies to improve immune responses to environmental pathogens, optimal growth and timely attainment of puberty in calves. The literature reviewed here shows that there are opportunities to enhance the future performance of cattle paying attention to the interaction of nutrition and immunity at each developmental stage. Therefore, the objective of this review is to give the reader an overview of interactions between immunity, growth and puberty in dairy calves and highlight how these influence future performances.

Maternal nutrient restriction in late pregnancy programs postnatal metabolism and pituitary development in beef heifers

Maternal undernutrition during pregnancy followed by ad libitum access to nutrients during postnatal life induces postnatal metabolic disruptions in multiple species. Therefore, an experiment was conducted to evaluate postnatal growth, metabolism, and development of beef heifers exposed to late gestation maternal nutrient restriction. Pregnancies were generated via transfer of in vitro embryos produced using X-bearing sperm from a single Angus sire. Pregnant dams were randomly assigned to receive either 100% (control; n = 9) or 70% (restricted; n = 9) of their total energy requirements from gestational day 158 to parturition. From post-natal day (PND) 301 until slaughter (PND485), heifers were individually fed ad libitum in a Calan gate facility. Calves from restricted dams were lighter than controls at birth (P<0.05) through PND70 (P<0.05) with no difference in body weight from PND105 through PND485 (P>0.10). To assess pancreatic function, glucose tolerance tests were performed on PND315 and PND482 and a diet effect was seen with glucose area under the curve being greater (P<0.05) in calves born to restricted dams compared to controls. At slaughter, total internal fat was greater (P<0.05) in heifers born to restricted dams, while whole pituitary weight was lighter (P<0.05). Heifers from restricted dams had fewer growth hormone-positive cells (somatotrophs) compared to controls (P<0.05). Results demonstrate an impaired ability to clear peripheral glucose in heifers born to restricted dams leading to increased deposition of internal fat. A reduction in the number of somatotrophs may contribute to the adipogenic phenotype of heifers born to restricted dams due to growth hormone’s known anabolic roles in growth, lipolysis, and pancreatic islet function.

The Influence of Maternal Dietary Intake During Mid-Gestation on Growth, Feedlot Performance, miRNA and mRNA Expression, and Carcass and Meat Quality of Resultant Offspring

This research analyzed how maternal plane of nutrition during mid-gestation impacts growth, blood metabolites, expression of microRNA and messenger RNA in skeletal muscle, feedlot performance, and carcass characteristics of progeny. Thirty-two cows were bred to the same Angus sire and fed to either maintain a body condition score (BCS) of 5.0 to 5.5 (maintenance [MAIN]; n = 15) or to lose 1 BCS (restriction [REST]; n = 17) over an 84-d period of mid-gestation. Following the second trimester, all cows were co-mingled and fed at maintenance for the remainder of gestation. Following the 84-d treatment period, REST cows had a lower (P &lt; 0.01) BCS than MAIN cows. At the end of the third trimester, there was no difference (P = 0.78) in BCS between the treatment groups. There was no difference (P &gt; 0.10) between offspring in birthweight, weaning weight, average daily gain, feed efficiency, dry matter intake, carcass yield, steak quality, or in circulating levels of glucose, cortisol, insulin, or insulin-like growth factor-1. REST offspring expressed more (P &lt; 0.05) miR-133a, miR-133b, miR-181d, miR-214, miR-424 and miR-486 at weaning than MAIN offspring. At harvest, REST offspring expressed more (P &lt; 0.05) miR-133a and less (P &lt; 0.01) miR-486 than MAIN offspring. REST steaks were perceived as more tender (P = 0.05) by a trained sensory panel. These results indicate that maternal nutrient restriction during mid-gestation resulting in a loss of 1 BCS has an effect on microRNA expression in the skeletal muscle but does not alter postnatal growth potential, carcass quality, or end product quality of the offspring. This suggests that moderate restriction in maternal nutrition during the second trimester, which results in a drop in BCS that can be recovered during the third trimester, should not cause alarm for producers when considering future offspring performance.

Satellite cells and their regulation in livestock

Satellite cells are the myogenic stem and progenitor population found in skeletal muscle. These cells typically reside in a quiescent state until called upon to support repair, regeneration, or muscle growth. The activities of satellite cells are orchestrated by systemic hormones, autocrine and paracrine growth factors, and the composition of the basal lamina of the muscle fiber. Several key intracellular signaling events are initiated in response to changes in the local environment causing exit from quiescence, proliferation, and differentiation. Signals emanating from Notch, wingless-type mouse mammary tumor virus integration site family members, and transforming growth factor-β proteins mediate the reversible exit from growth 0 phase while those initiated by members of the fibroblast growth factor and insulin-like growth factor families direct proliferation and differentiation. Many of these pathways impinge upon the myogenic regulatory factors (MRF), myogenic factor 5, myogenic differentiation factor D, myogenin and MRF4, and the lineage determinate, Paired box 7, to alter transcription and subsequent satellite cell decisions. In the recent past, insight into mouse transgenic models has led to a firm understanding of regulatory events that control satellite cell metabolism and myogenesis. Many of these niche-regulated functions offer subtle differences from their counterparts in livestock pointing to the existence of species-specific controls. The purpose of this review is to examine the mechanisms that mediate large animal satellite cell activity and their relationship to those present in rodents.

Pregnant beef cow's nutrition and its effects on postnatal weight and carcass quality of their progeny

A systematic review (SR) and meta-analysis (MA) were performed to evaluate the effects of different energy levels (metabolizable energy, ME) and crude protein (CP), supplied to pregnant cows, on weight of their progenies at 60 (BW60), 100 (BW100), 180 (BW180) and 205 (BW205) days of age, average daily gain (ADG), and weight, age, loin eye area (LEA), marbling and fat thickness (FT) at slaughter. The SR was performed on two electronic databases. The MA for random effects was performed for each response variable separately. The BW60 was reduced (P<0.001; I² = 78.9%) when cows consumed CP and ME above the required levels during the third trimester of pregnancy (3TRI). The BW205 was lower (P<0.001; I² = 92.6%) when cows consumed ME above the recommended levels in the second trimester of pregnancy (2TRI) and 3TRI. Conversely, the ADG was higher when cows consumed CP (P = 0.032; I² = 96.1%) and ME (P<0.001; I² = 96.1%) above the required levels. The steers whose mothers consumed CP and ME above the required levels during the 3TRI were slaughtered 5.5 days earlier (P = 0.015; I² = 98.5%) compared to other steers. The marbling was higher (P<0.001; I² = 91.7%) in calves born to mothers consuming CP and ME above the recommended levels, regardless of the gestation phase. The FT was higher (P<0.001; I² = 0%) in the offspring of cows that consumed CP and ME above the required levels during the 3TRI. Thus, CP and ME intake, at levels higher than those recommended by the NRC, by pregnant cows in the 3TRI reduces the progeny weight up to 205 days of age. However, this is advantageous during the finishing phase, as it reduces slaughter age and increases the ADG and carcass quality by improving marbling and FT.

Prediction of the Secretome and the Surfaceome: A Strategy to Decipher the Crosstalk between Adipose Tissue and Muscle during Fetal Growth

Crosstalk between adipose and muscular tissues is hypothesized to regulate the number of muscular and adipose cells during fetal growth, with post-natal consequences on lean and fat masses. Such crosstalk largely remains, however, to be described. We hypothesized that a characterization of the proteomes of adipose and muscular tissues from bovine fetuses may enhance the understanding of the crosstalk between these tissues through the prediction of their secretomes and surfaceomes. Proteomic experiments have identified 751 and 514 proteins in fetal adipose tissue and muscle. These are mainly involved in the regulation of cell proliferation or differentiation, but also in pathways such as apoptosis, Wnt signalling, or cytokine-mediated signalling. Of the identified proteins, 51 adipokines, 11 myokines, and 37 adipomyokines were predicted, together with 26 adipose and 13 muscular cell surface proteins. Analysis of protein–protein interactions suggested 13 links between secreted and cell surface proteins that may contribute to the adipose–muscular crosstalk. Of these, an interaction between the adipokine plasminogen and the muscular cell surface alpha-enolase may regulate the fetal myogenesis. The in silico secretome and surfaceome analyzed herein exemplify a powerful strategy to enhance the elucidation of the crosstalk between cell types or tissues.

Poor maternal nutrition during gestation in sheep alters prenatal muscle growth and development in offspring

Poor maternal nutrition during gestation can have immediate and life-long negative effects on offspring growth and health. In livestock, this leads to reduced product quality and increased costs of production. Based on previous evidence that both restricted- and overfeeding during gestation decrease offspring muscle growth and alter metabolism postnatally, we hypothesized that poor maternal nutrition during gestation would reduce the growth and development of offspring muscle prenatally, reduce the number of myogenic progenitor cells, and result in changes in the global expression of genes involved in prenatal muscle development and function. Ewes were fed a control (100% NRC)-, restricted (60% NRC)-, or overfed (140% NRC) diet beginning on day 30 of gestation until days 45, 90, and 135 of gestation or until parturition. At each time point fetuses and offspring (referred to as CON, RES, and OVER) were euthanized and longissimus dorsi (LM), semitendinosus (STN), and triceps brachii (TB) were collected at each time point for histological and RNA-Seq analysis. In fetuses and offspring, we did not observe an effect of diet on cross-sectional area (CSA), but CSA increased over time (P < 0.05). At day 90, RES and OVER had reduced secondary:primary muscle fiber ratios in LM (P < 0.05), but not in STN and TB. However, in STN and TB percent PAX7-positive cells were decreased compared with CON (P < 0.05). Maternal diet altered LM mRNA expression of 20 genes (7 genes downregulated in OVER and 2 downregulated in RES compared with CON; 5 downregulated in OVER compared with RES; false discovery rate (FDR)-adj. P < 0.05). A diet by time interaction was not observed for any genes in the RNA-Seq analysis; however, 2,205 genes were differentially expressed over time between days 90 and 135 and birth (FDR-adj. P < 0.05). Specifically, consistent with increased protein accretion, changes in muscle function, and increased metabolic activity during myogenesis, changes in genes involved in cell cycle, metabolic processes, and protein synthesis were observed during fetal myogenesis. In conclusion, poor maternal nutrition during gestation contributes to altered offspring muscle growth during early fetal development which persists throughout the fetal stage. Based on muscle-type-specific effects of maternal diet, it is important to evaluate more than one type of muscle to fully elucidate the effects of maternal diet on offspring muscle development.

TRIENNIAL GROWTH SYMPOSIUM: THE NUTRITION OF MUSCLE GROWTH: Impacts of nutrition on the proliferation and differentiation of satellite cells in livestock species1,2

Nutrition and other external factors are known to have a marked effect on growth of skeletal muscle, modulated, at least in part, through effects on satellite cells. Satellite cells and their embryonic precursors play an integral role in both prenatal and postnatal skeletal muscle growth of mammals. Changes in maternal nutrition can impact embryonic muscle progenitor cells which ultimately impacts both prenatal and postnatal skeletal muscle development. Satellite cells are important in postnatal skeletal muscle growth as they support the hypertrophy of existing myofibers. Hypertrophy of existing fibers is the only mechanism of postnatal muscle growth because muscle fiber number is fixed at birth and fiber nuclei have exited the cell cycle. Because fiber nuclei do not divide, additional nuclei required for hypertrophy must be acquired from satellite cells. To date, little research has aimed at determining whether nutrition directly impacts satellite cell populations within skeletal muscle of livestock species. However, it is well established that nutrition alters circulating concentrations of various growth factors such as insulin-like growth factor 1, epidermal growth factor, hepatocyte growth factor, and fibroblast growth factor. Each of these different growth factors impacts satellite cell proliferation and/or activation, indicating that nutrition likely plays a large role in skeletal muscle growth through impacting the satellite cell pool in both prenatal and postnatal growth. The relationship among nutrition, growth factors, and satellite cells relative to skeletal muscle growth is an important area of research that warrants further consideration.

Effect of maternal feed restriction in dairy goats at different stages of gestation on skeletal muscle development and energy metabolism of kids at the time of births

The aim was to determine effects of maternal feed restriction in dairy goats at gestational different stages on skeletal muscle development and energy metabolism in kids at birth. Six pregnant goats were fed 50% of total digestible nutrients (TDN) and crude protein (CP) (NRC, 2007) recommendations in the first half of gestation and then fed to 100% of the recommendations in the second half of gestation (treatment R-M). In the other group, eight pregnant goats were fed 100% of TDN and CP in the first half of gestation and 50% of a restricted diet the second half of gestation (treatment M-R). Birth weight, blood glucose concentration, muscle fiber number, and size of kids at birth were not affected by maternal feed restriction. The mRNA and protein abundance of myogenic, adipogenic and fibrogenic markers were not affected (P > 0.05) by maternal diet. With regard to values for variables in kid energy metabolism, mRNA abundance of the glycolic enzyme HKII was less (P = 0.03) in the M-R group. In conclusion, maternal feed restriction in the first or second half of gestation had no affect mRNA abundance on myogenic, adipogenic, and fibrogenic markers nor were there changes in skeletal muscle mesenchymal stem cell population of kids at the time of birth. There, however, may be detrimental effects on energy metabolism by reducing HKII gene expression in skeletal muscle of dairy goat kids at the time of birth.

Moderate nutrient restriction of beef heifers alters expression of genes associated with tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum by day 50 of gestation

We hypothesized that a moderate maternal nutrient restriction during the first 50 d of gestation in beef heifers would affect transcript abundance of genes associated with tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum. Angus-cross heifers were estrus synchronized and assigned at breeding to one of two dietary treatments (CON- 100% of nutrient requirements to gain 0.45 kg/d; RES- 60% of CON). At day 50 of gestation, 14 heifers were ovariohysterectomized, and fetal liver, muscle, and cerebrum were collected. Transcriptome analysis via RNA-seq was conducted on the Illumina HiSeq 2500 platform using 50-bp paired-end reads at a depth of 2 × 10.4M reads/sample. Bioinformatic analysis was performed using the Tuxedo Suite and ontological analysis with DAVID 6.8. For fetal liver, muscle, and cerebrum, a total of 548, 317, and 151 genes, respectively (P < 0.01) were differentially expressed, of which 201, 144, and 28 genes, respectively were false discovery rate protected (FDR; q < 0.10). Differentially expressed genes were screened for fit into functional categories of pathways or ontologies associated with known impacts on tissue metabolism, accretion, and function. In fetal liver, five functional categories of interest (n = 125 genes) were affected by nutritional treatment: metabolic pathways, protein kinase, nucleosome core, mRNA splicing, and complement/coagulation cascades, of which 105 genes were upregulated in RES. In fetal muscle, three functional categories of interest (n = 106 genes) were affected by nutritional treatment: skeletal muscle, embryogenesis, and signaling cascades, of which 64 genes were upregulated in RES. In fetal cerebrum, three functional categories of interest (n = 60 genes) were affected by nutritional treatment: hippocampus and neurogenesis, metal-binding, and cytoskeleton, of which 58 genes were upregulated in RES. These results demonstrate that a moderate maternal nutrient restriction during the first 50 d of gestation in beef heifers alters transcript abundance of genes potentially impacting tissue metabolism, accretion, and function in fetal liver, muscle, and cerebrum. Furthermore, these results indicate that affected categories are tissue-specific and moderate maternal nutrient restriction generally increases expression of genes in fetuses from RES fed dams. Finally, these data lay the foundation upon which further research that identifies phenotypic responses to changes in these pathways may be elucidated.

Maternal nutrient restriction alters uterine artery hemodynamics and placentome vascular density in Bos indicus and Bos taurus

The objective was to examine uterine artery blood flow (UBF) as well as macroscopic and microscopic placentome vascular density in nutrient-restricted Angus and Brahman heifers. Angus (n = 6) and Brahman (n = 6) heifers were bred to a single sire and pregnancy confirmed at 30-d postbreeding. Heifers were randomly assigned to 1 of 2 dietary treatments consisting of 100% (control-fed; CON; n = 6) or 60% (total nutrient-restricted; RES; n = 6) based from net energy requirements for gestating heifers. Nutritional treatments were imposed from days 50 to 180 of gestation. On day 175 of gestation, UBF was collected ipsilateral and contralateral to the conceptus via Doppler ultrasonography. Heifers underwent Cesarean sections for collection of 2 adjacent placentomes on day 180 of gestation. The primary cotyledonary artery of 1 placentome was perfused with Alexa Fluor 647 Con A conjugate to examine macroscopic cotyledonary vascular density via an in vivo imaging system. The second placentome was fixed for microscopic immunofluorescence labeling of capillaries and separated into maternal (caruncle) and fetal (cotyledon) components for determination of angiogenic factor mRNA expression. Main effects of nutritional treatment and breed are reported in the absence of a significant nutritional treatment by breed interaction. Ipsilateral UBF was decreased (P < 0.05) by 48% in RES vs. CON, whereas breed did not influence ipsilateral UBF. Contralateral UBF was not different between nutritional treatments; however, contralateral UBF was decreased (P < 0.05) by 63% in Brahman vs. Angus cattle. Macroscopic cotyledonary vascular density was increased (P < 0.05) by 36% in RES vs. CON and 82% in Brahman vs. Angus heifers. Percent capillary area and capillary perimeter were increased (P < 0.05) in RES vs. CON and increased (P < 0.05) in Brahman vs. Angus heifers. Dietary treatments did not alter angiogenic factor expression; however, transcript abundance of caruncle and cotyledon ANGP1, FLT1, and KDR was increased (P < 0.05) in Brahman vs. Angus heifers. In summary, these data indicate compensatory responses in macroscopic and microscopic placentome blood vessel density during maternal nutrient restriction-induced reductions in UBF. Moreover, a greater macroscopic density of cotyledonary blood vessels was observed in Brahman vs. Angus heifers.

Effects of realimentation after nutrient restriction during mid- to late gestation on pancreatic digestive enzymes, serum insulin and glucose levels, and insulin-containing cell cluster morphology

This study examined effects of stage of gestation and nutrient restriction with subsequent realimentation on maternal and foetal bovine pancreatic function. Dietary treatments were assigned on day 30 of pregnancy and included: control (CON; 100% requirements; n = 18) and restricted (R; 60% requirements; n = 30). On day 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or realimented to control (RC; n = 11). On day 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5) or realimented to control (RRC, n = 6). On day 254, the remaining cows were slaughtered and serum samples were collected from the maternal jugular vein and umbilical cord to determine insulin and glucose concentrations. Pancreases from cows and foetuses were removed, weighed, and subsampled for enzyme and histological analysis. As gestation progressed, maternal pancreatic α-amylase activity decreased and serum insulin concentrations increased (p ≤ 0.03). Foetal pancreatic trypsin activity increased (p < 0.001) with advancing gestation. Foetal pancreases subjected to realimentation (CCC vs. RCC and RRC) had increased protein and α-amylase activity at day 254 (p ≤ 0.02), while trypsin (U/g protein; p = 0.02) demonstrated the opposite effect. No treatment effects were observed for maternal or foetal pancreatic insulin-containing cell clusters. Foetal serum insulin and glucose levels were reduced with advancing gestation (p ≤ 0.03). The largest maternal insulin-containing cell cluster was not influenced by advancing gestation, while foetal clusters grew throughout (p = 0.01). These effects indicate that maternal digestive enzymes are influenced by nutrient restriction and there is a potential for programming of increased foetal digestive enzyme production resulting from previous maternal nutrient restriction.

Analysis of the relationship between insulin-like growth factor 1 receptor gene polymorphisms in Montbeliarde cows and the birth weight of their calves

Montbeliarde is a cattle breed of combined milk and meat performance type, which unlike the other breeds is characterized by several positive features, such as better health, high resistance to mastitis, calving ease and good weight gain. The study involved a population of 163 Montbeliarde cows. In view of the substantial role of the IGF-I/IGF-IR system in growth and development, the aim of this study was to show an association between insulin-like growth factor 1 receptor gene polymorphisms in Montbeliarde cows and birth weight of their offspring. Three single nucleotide polymorphisms within the IGF1R gene were analyzed using PCR-RFLP or ACRS-PCR methods. The frequencies of the most common genotypes were as follows: CC 0.90 (IGF1R/TaiI), GG 0.77 (IGF1R/MspI) and GG 0.58 (IGF1R/TaqI). A total of 14 combinations was compared, from which due to the low frequency (n < 10) only 4 were used for calculations. In the analysed herd, the mean body weight of calves regardless of the calving order was always the highest in animals with maternal CC / GG / AA combined genotype. This observation was confirmed statistically both for the individual genotypes as well as in the case of cows carrying such a combination at the same time (P < 0.01). Therefore, IGF1R may be considered as a promising candidate gene for the identification of molecular markers predicting meat quality in cattle.

Effects of Added Zinc on Skeletal Muscle Morphometrics and Gene Expression of Finishing Pigs Fed Ractopamine-HCL

Finishing pigs (n = 320) were used in a 35-day study to determine the effects of ractopamine-HCl (RAC) and supplemental Zinc (Zn) level on loin eye area (LEA) and gene expression. Pens were randomly allotted to the following treatments for the final 35 days on feed: a corn-soybean meal diet (CON), a diet with 10 ppm RAC (RAC+), and RAC diet plus added Zn at 75, 150, or 225 ppm. Sixteen pigs per treatment were randomly selected for collection of serial muscle biopsies and carcass data on day 0, 8, 18, and 32 of the treatment phase. Compared to CON carcasses, RAC+ carcasses had 12.6% larger (P = 0.03) LEA. Carcasses from RAC diets with added Zn had a tendency for increased (quadratic, P < 0.10) LEA compared to the RAC+ carcasses. Compared to RAC+ pigs, relative expression of IGF1 decreased with increasing levels of Zn on day 8 and 18 of treatment, but expression levels were similar on day 32 due to Zn treatments increasing in expression while the RAC+ treatment decreased (Zn quadratic × day quadratic, P = 0.04). A similar trend was detected for the expression of β1-receptor where expression levels in the RAC+ pigs were greater than Zn supplemented pigs on day 8 and 18 of the experiment, but the magnitude of difference between the treatments was reduced on day 32 due to a decrease in expression by RAC+ pigs and an increase in expression by the Zn pigs (Zn quadratic × day quadratic, P = 0.01). The ability of Zn to prolong the expression of these two genes may be responsible for the tendency of Zn to increase LEA in RAC supplemented pigs.

The influence of maternal energy status during mid-gestation on beef offspring tenderness, muscle characteristics, and gene expression

The objective of this study was to determine if maternal energy status during mid-gestation influences the expression of genes regulating muscle and fat development, and muscle characteristics that may impact meat tenderness. Cows grazed dormant, native range (Positive Energy Status [PES]) or were fed at 80% of maintenance energy requirements (Negative Energy Status [NES]) during mid-gestation. Steer offspring were harvested after 21 d in the feedlot (weaning subsample) or after 208 d in the feedlot (final subsample). Greater 21-d tenderness was observed in NES steers, resulting from reduced collagen content in longissimus lumborum steaks. In the semitendinosus, NES steers had greater soluble collagen, and down-regulated expression of MHC-IIA and TIMP-3 at weaning, while MHC-IIA expression was up-regulated in NES steers in the final harvest. Data show mid-gestational maternal energy status may impact offspring tenderness and collagen, but differences were not detected in expression of genes important in myogenesis and adipogenesis in muscle samples obtained from steers at weaning or slaughter.

Poor maternal nutrition inhibits muscle development in ovine offspring

BACKGROUND

Maternal over and restricted nutrition has negative consequences on the muscle of offspring by reducing muscle fiber number and altering regulators of muscle growth. To determine if over and restricted maternal nutrition affected muscle growth and gene and protein expression in offspring, 36 pregnant ewes were fed 60%, 100% or 140% of National Research Council requirements from d 31 ± 1.3 of gestation until parturition. Lambs from control-fed (CON), restricted-fed (RES) or over-fed (OVER) ewes were necropsied within 1 d of birth (n = 18) or maintained on a control diet for 3 mo (n = 15). Semitendinosus muscle was collected for immunohistochemistry, and protein and gene expression analysis.

RESULTS

Compared with CON, muscle fiber cross-sectional area (CSA) increased in RES (58%) and OVER (47%) lambs at 1 d of age (P < 0.01); however at 3 mo, CSA decreased 15% and 17% compared with CON, respectively (P < 0.01). Compared with CON, muscle lipid content was increased in OVER (212.4%) and RES (92.5%) at d 1 (P < 0.0001). Muscle lipid content was increased 36.1% in OVER and decreased 23.6% in RES compared with CON at 3 mo (P < 0.0001). At d 1, myostatin mRNA abundance in whole muscle tended to be greater in OVER (P = 0.07) than CON. Follistatin mRNA abundance increased in OVER (P = 0.04) and tended to increase in RES (P = 0.06) compared with CON at d 1. However, there was no difference in myostatin or follistatin protein expression (P > 0.3). Phosphorylated Akt (ser473) was increased in RES at 3 mo compared with CON (P = 0.006).

CONCLUSIONS

In conclusion, maternal over and restricted nutrient intake alters muscle lipid content and growth of offspring, possibly through altered gene and protein expression.