Effect of maternal dietary restriction during pregnancy on lamb carcass characteristics and muscle fiber composition1

The characteristics, influence factors, and regulatory strategies of growth retardation in ruminants: a review

Growth retardation represents a main barrier to affect the productivity and efficiency of ruminants production, which is characterized by low growth rate, a disparity between skeletal and physiological maturation, gastrointestinal dysfunction and reduced reproductive performance. This review provides a concise overview of growth retardation in ruminants, and summarizes the key factors that influence their growth and development, including genetics, nutrition, microbiota and environment. Also, this review emphasizes the central role of nutritional management and gastrointestinal development, as well as the regulatory mechanisms involved in growth processes. In addition, recent advances in these aspects are discussed to form an integrative framework aimed at improving physiological function in ruminants. This review provides a comprehensive perspective for understanding the complex mechanism of growth retardation in ruminants, puts forward a theoretical basis for optimizing the production efficiency of ruminants industry and emphasizes the importance of multidisciplinary collaboration to provide a reference for advancing systematic research on growth and development of ruminants.

Mature adipocytes inhibit differentiation of myogenic cells but stimulate proliferation of fibro-adipogenic precursors derived from trout muscle in vitro

Interactions between tissues and cell types, mediated by cytokines or direct cell-cell exchanges, regulate growth. To determine whether mature adipocytes influence the in vitro growth of trout mononucleated muscle cells, we developed an indirect coculture system, and showed that adipocytes (5 × 106 cells/well) derived from perivisceral adipose tissue increased the proliferation (BrdU-positive cells) of the mononucleated muscle cells (26% vs. 39%; p < 0.001) while inhibiting myogenic differentiation (myosin+) (25% vs. 15%; p < 0.001). Similar effects were obtained with subcutaneous adipose tissue-derived adipocytes, although requiring more adipocytes (3 × 107 cells/well vs. 5 × 106 cells/well). Conditioned media recapitulated these effects, stimulating proliferation (31% vs. 39%; p < 0.001) and inhibiting myogenic differentiation (32 vs. 23%; p < 0.001). Adipocytes began to reduce differentiation after 24 h, whereas proliferation stimulation was observed after 48 h. While adipocytes did not change pax7+ and myoD1/2+ percentages, they reduced myogenin+ cells showing inhibition from early differentiation stage. Finally, adipocytes increased BrdU+ cells in the Pdgfrα+ population but not in the myoD+ one. Collectively, our results demonstrate that trout adipocytes promote fibro-adipocyte precursor proliferation while inhibiting myogenic cells differentiation in vitro, suggesting the key role of adipose tissue in regulating fish muscle growth.

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.

Comparison of muscle fiber characteristics and meat quality between newborn and adult Haimen goats

Goat meat is popular with consumers for its rich nutritional content. Muscle fiber characteristics have been shown to play a crucial role in determining the quantity and quality of meat. However, little is known about the temporal changes in muscle fiber characteristics and meat quality during growth in goats. In this study, muscle fiber type, fiber diameter, fiber cross-sectional area (CSA), glycolytic potential (GP), meat pH, and meat color were analyzed in the gastrocnemius (GAS), gluteus medius (GM), biceps brachii (BB), longissimus lumborum (LL) muscles from newborn (NHMG) and adult (AHMG) Haimen goats. The distribution of type I and type Π fiber in goats is not consistent across the four muscles and undergoes alterations with age. The diameter and CSA of the muscle fibers were similar among the four NHMG muscles. However, in AHMG, the LL muscle had the largest fiber in terms of both diameter and CSA, followed by BB, GM, and GAS muscles. Moreover, the CSA of type Π fibers was higher than that of type I fibers in both NHMG and AHMG. GP values ranged from 90 to 140 umol/g across the muscle and no significant differences were observed. AHMG had a higher pH level and a* value, but lower L* and b* values than NHMG. Overall, our findings enhance our understanding of the changes in muscle fiber type and meat quality during the growth in Haimen goats and provide a basis for future research on the development and transformation of muscle fibers in goats.

Transgenerational transmission of environmental effects in livestock in the age of global warming

Recent decades provide mounting evidence for the continual increase in global temperatures, now termed "global warming," to the point of drastic worldwide change in the climate. Climatic change is a long-term shift in temperatures and weather patterns, including increased frequency and intensity of extreme environmental events such as heat waves accompanied by extreme temperatures and high humidity. Climate change and global warming put several challenges to the livestock industry by directly affecting the animal's production, reproduction, health, and welfare. The broad impact of global warming, and in particular heat stress, on-farm animals' performance has been comprehensively studied. It has been estimated that the US livestock industry's loss caused by heat stress is up to $2.4 billion annually. However, the long-term intergenerational and transgenerational effects of climatic change and global warming on farm animals are sparse. Transgenerational effects, which are mediated by epigenetic mechanisms, can affect the animal's performance regardless of its immediate environment by altering its phenotypic expression to fit its ancestors' environment. In many animal species, environmental effects are epigenetically encoded within a narrow time interval during the organism's gametogenesis, and these epigenetic modifications can then be intergenerationally transmitted. Several epigenetic mechanisms mediate intergenerational transmission of environmental effects, typically in a parent-dependent manner. Therefore, exposure of the animal to an extreme climatic event and other environmental stressors during gametogenesis can undergo epigenetic stabilization in the germline and be passed to the offspring. As a result, the offspring might express a phenotype adjusted to fit the stressors experienced by their ancestors, regardless of their direct environment. The purpose of this perspective is to review current evidence for intergenerational and transgenerational transmission of environmental stress effects, specifically in the context of global warming and climate change, and to offer viewpoints on the possible impacts on the livestock industry.

Impact of fetal exposure to mycotoxins on longissimus muscle fiber hypertrophy and miRNA profile

BACKGROUND

Longissimus muscle samples were collected from lambs exposed in utero to mycotoxins [E-, endophyte-free tall fescue seed without ergot alkaloids (negative control) or E + , endophyte-infected tall fescue seed containing ergot alkaloids] during mid-gestation (MID; E + /E-) or late-gestation (LATE; E-/E +) harvested at two developmental stages (FETAL, gestational d133) or (MAT, near maturity, 250 d of age; n = 3/treatment/developmental stage). Muscle samples were examined to determine the impact of in utero mycotoxin exposure on skeletal muscle fiber hypertrophy and the miRNA profile at FETAL and MAT.

RESULTS

Longissimus weight was greater (P < 0.05) in E + /E- lambs compared to E-/E + lambs at MAT; however, FETAL longissimus weight did not differ (P > 0.10) between fescue treatments. Type I fiber cross sectional area was larger (P < 0.10) for E + /E- than E-/E + at MAT but did not differ (P > 0.10) between fescue treatments at FETAL. Type II fiber area was larger (P < 0.05) at MAT in E + /E- compared to E-/E + but did not differ (P < 0.05) between fescue treatments at FETAL. Cross-sectional Type I and Type II longissimus muscle fiber area increased (P < 0.05) from FETAL to MAT by 6.86-fold and 10.83-fold, respectively. The ratio of Type II:Type I muscle fibers was lower (P = 0.04) at MAT compared to FETAL. There were 120 miRNA differentially expressed (q < 0.05) between FETAL and MAT. Maternal fescue treatment did not alter (q > 0.05) expression of miRNAs in the longissimus muscle. miR-133, -29a, -22-3p, and -410-3p were identified as highly significant with a log₂ fold change > 4. In vitro satellite cell cultures showed that selected miRNAs (miR-22-3p, 29a, 27a, and 133a) are differentially regulated during proliferation and differentiation indicating a role of miRNA in muscle hypertrophy.

CONCLUSIONS

Exposure to mycotoxins did not alter fiber type but had long-term impacts on postnatal muscle hypertrophy and cross-sectional area. The miRNA profile of the longissimus was not altered by Maternal mycotoxin exposure at FETAL or MAT. Developmental age altered the miRNA transcriptome and mRNA expression of known genes related to muscle growth. These results indicate that Maternal exposure to E + fescue seed during LATE gestation can alter postnatal muscle hypertrophy in sheep; however, these changes are not regulated by the miRNA transcriptome of the longissimus muscle.

Effects of Maternal Nutrient Restriction and Melatonin Supplementation on Cardiomyocyte Cell Development Parameters Using Machine Learning Techniques

The objective of the current study was to examine the effects of maternal feed restriction and melatonin supplementation on fetal cardiomyocyte cell development parameters and predict binucleation and hypertrophy using machine learning techniques using pregnant beef heifers. Brangus heifers (n = 29) were assigned to one of four treatment groups in a 2 × 2 factorial design at day 160 of gestation: (1) 100% of nutrient requirements (adequately fed; ADQ) with no dietary melatonin (CON); (2) 100% of nutrient requirements (ADQ) with 20 mg/d of dietary melatonin (MEL); (3) 60% of nutrient requirements (nutrient-restricted; RES) with no dietary melatonin (CON); (4) 60% of nutrient requirements (RES) with 20 mg/d of dietary melatonin (MEL). On day 240 of gestation, fetuses were removed, and fetal heart weight and thickness were determined. The large blood vessel perimeter was increased in fetuses from RES compared with ADQ (p = 0.05). The total number of capillaries per tissue area exhibited a nutrition by treatment interaction (p = 0.01) where RES-MEL increased capillary number compared (p = 0.03) with ADQ-MEL. The binucleated cell number per tissue area showed a nutrition by treatment interaction (p = 0.010), where it was decreased in RES-CON vs. ADQ-CON fetuses. Hypertrophy was estimated by dividing ventricle thickness by heart weight. Based on machine learning results, for the binucleation and hypertrophy target variables, the Bagging model with 5 Decision Tree estimators and 3 Decision Tree estimators produced the best results without overfitting. In the prediction of binucleation, left heart ventricular thickness feature had the highest Gin importance weight followed by fetal body weight. In the case of hypertrophy, heart weight was the most important feature. This study provides evidence that restricted maternal nutrition leads to a reduction in the number of cardiomyocytes while melatonin treatment can mitigate some of these disturbances.

Effects of Maternal Nutrition on Female Offspring Weight Gain and Sexual Development

Maternal nutrition during pregnancy influences postnatal life of animals; nevertheless, few studies have investigated its effects on the productive performance and reproductive development of heifers. This study evaluated the performance, reproductive development, and correlation between reproduction × fat thickness and performance × ribeye area (REA) traits of heifers. We also performed an exploratory genomic association during the rearing period in heifers submitted to fetal programming. The study comprised 55 Nellore heifers born to dams exposed to one of the following nutritional planes: control, without protein-energy supplementation; PELT, protein-energy last trimester, protein-energy supplementation offered in the final third of pregnancy; and PEWG, protein-energy whole gestation, protein-energy supplementation upon pregnancy confirmation. Protein-energy supplementation occurred at the level of 0.3% live weight. After weaning, heifers were submitted to periodic evaluations of weight and body composition by ultrasonography. From 12 to 18 months, we evaluated the reproductive tract of heifers to monitor its development for sexual precocity and ovarian follicle population. The treatments had no effect (p > 0.05) on average daily gain; however, the weight of the animals showed a significant difference over time (p = 0.017). No differences were found between treatments for REA, backfat, and rump fat thickness, nor for puberty age, antral follicular count, and other traits related to reproductive tract development (p > 0.05). The correlation analysis between performance traits and REA showed high correlations (r > 0.37) between REA at weaning and year versus weight from weaning until yearling; however, no correlation was found for reproductive development traits versus fat thickness (p > 0.05). The exploratory genomic association study showed one single-nucleotide polymorphism (SNP) for each treatment on an intergenic region for control and PEWG, and the one for PELT on an intronic region of RAPGEF1 gene. Maternal nutrition affected only the weight of the animals throughout the rearing period.

Life Course Impact of Glucocorticoids During Pregnancy on Muscle Development and Function

Maternal stress, such as maternal obesity, can induce severe gestational disease and hormonal disorder which may disrupt fetal organ maturation and further cause endangered early or future health in offspring. During fetal development, glucocorticoids are essential for the maturation of organ systems. For instance, in clinical applications, glucocorticoids are commonly utilized to pregnant women with the risk of preterm delivery to reduce mortality of the newborns. However, exposure of excessive glucocorticoids at embryonic and fetal developmental stages can cause diseases such as cardiovascular disease and muscle atrophy in adulthood. Effects of excessive glucocorticoids on human health are well-recognized and extensively studied. Nonetheless, effects of these hormones on farm animal growth and development, particularly on prenatal muscle development, and postnatal growth, did not attract much attention until the last decade. Here, we provided a short review of the recent progress relating to the effect of glucocorticoids on prenatal skeletal muscle development and postnatal muscle growth as well as heart muscle development and cardiovascular disease during life course.

Use of Agriculturally Important Animals as Models in Biomedical Research

Livestock have contributed significantly to advances in biomedicine and offer unique advantages over rodent models. The human is the ideal biomedical model; however, ethical reasons limit the testing of hypotheses and treatments in humans. Rodent models are frequently used as alternatives to humans due to size, low cost, and ease of genetic manipulation, and have contributed tremendously to our understanding of human health and disease. However, the use of rodents in translational research pose challenges for researchers due to physiological differences to humans. The use of livestock species as biomedical models can address these challenges as livestock have several similarities to human anatomy, physiology, genetics, and metabolism and their larger size permits collection of more frequent and often larger samples. Additionally, recent advances in genetics in livestock species allow for studies in genomics, proteomics, and metabolomics, which have the added benefit of applications to both humans in biomedical research and livestock in improving production. In this review, we provide an overview of scientific findings using livestock and benefits of each model to the livestock industry and to biomedical research.

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.

Gestational nutrient restriction under extensive grazing conditions: Effects on muscle characteristics and meat quality in heavy lambs

We evaluated maternal undernutrition effects induced by a lower natural pasture allowance (gestation days 30-143) on histological-biochemical and meat traits in muscles Semitendinosus, cranial Gluteobiceps and Supraspinatus from 200-day old male and female lambs. Maternal undernutrition increased oxidative and reduced glycolytic fibers in all muscles (P ≤ 0.01). Maternal undernutrition reduced the diameter of glycolytic fibers in the cranial Gluteobiceps of exclusively female lambs (P = 0.05) and reduced the diameter of oxidative fibers in the Supraspinatus of exclusively male lambs (P = 0.02). Maternal undernutrition increased lipid content in the Supraspinatus of females (P = 0.001), reduced lactate content (P = 0.03) and WB shear force (P = 0.02) in the Semitendinosus of females, and increased cooking losses in the Semitendinosus of males (P = 0.0069). In conclusion, gestational nutrient restriction induced fetal programming effects on muscle characteristics of lambs. Moreover, our study demonstrates that maternal undernutrition influences muscle and meat characteristics in a sex and muscle-dependent way.

Skeletal Muscle Development in Postnatal Beef Cattle Resulting from Maternal Protein Restriction during Mid-Gestation

We aimed to investigate the effects of maternal protein restriction during mid-gestation on the skeletal muscle composition of the offspring. In the restriction treatment (RES, n = 9), cows were fed a basal diet, while in the control (CON, n = 9) group cows received the same RES diet plus the protein supplement during mid-gestation (100-200d). Samples of Longissimus dorsi muscle were collected from the offspring at 30d and 450d postnatal. Muscle fiber number was found to be decreased as a result of maternal protein restriction and persisted throughout the offspring's life (p < 0.01). The collagen content was enhanced (p < 0.05) due to maternal protein restriction at 30d. MHC2X mRNA expression tended to be higher (p = 0.08) in RES 30d offspring, however, no difference (p > 0.05) was found among treatments at 450d. Taken together, our results suggest that maternal protein restriction during mid-gestation has major and persistent effects by reducing muscle fiber formation and may slightly increase collagen accumulation in the skeletal muscle of the offspring. Although maternal protein restriction may alter the muscle fiber metabolism by favoring the establishment of a predominant glycolytic metabolism, the postnatal environment may be a determinant factor that establishes the different proportion of muscle fiber types.

Maternal nutrient restriction alters endocrine pancreas development in fetal heifers

Maternal nutrient restriction during pregnancy alters fetal programming, which modifies the growth and health of the offspring in postnatal life. In cattle, nutrient restriction during pregnancy can be a result of environmental or economic factors, but little is known about how it alters the physiology of the fetus and affects future reproductive or growth efficiency. This study used female monozygotic twins, produced through in vitro fertilization and embryo splitting, to determine the effect of moderate maternal nutrient restriction on fetal development. Recipient Angus cross heifers pregnant with one twin were fed a diet meeting 100% National Research Council (NRC) total energy requirements (n = 4; control), whereas recipient heifers pregnant with the second twin were fed at 70% of NRC total energy requirements (n = 4; restricted) from gestational day (GD) 158 to GD 265 in Calan gate feeders. Recipient heifers were killed at GD 265. Change in maternal metabolic body weight was greater from zero in restricted heifers than controls (P < 0.05); restricted heifers lost weight during the nutrient restriction period. There was no difference in last rib back fat or rib eye area between groups (P > 0.10). There was no difference in fetal weight, uterine weight, or total placentome weight between groups (P > 0.10). The pancreas weight was reduced in restricted fetuses compared with control fetuses (P < 0.01), but there were no other differences in fetal organ weights (P > 0.10). Plasma insulin concentrations were reduced in restricted fetuses compared with controls (P < 0.01), but there was no effect of maternal diet on plasma glucose or glucagon concentrations in the fetus (P > 0.10). Histological analyses of the fetal pancreas revealed no differences in endocrine cell number or localization. Results indicate that a modest late gestation nutritional restriction impairs development of the fetal pancreas in the cow. Additional research will be needed to determine if these developmental changes lead to altered glucose and insulin homeostasis in the adult.

Fetal programming in sheep: effects on pre- and postnatal development in lambs

This systematic review and meta-analysis aim to summarize the effects of maternal undernutrition or overnutrition during pregnancy on fetal weight and morphometric measurements during pregnancy, at birth, and postnatal period in sheep. After completing the search, selection, and data extraction steps, the measure of effect was generated by the individual comparison of each indicator with the average of the control and treated group (undernutrition or overnutrition) using the DerSimonian and Laird method for random effects. Subgroup analyses were also performed for lambing order, litter size, sex, as well as level, timing, and duration of the intervention. Fetal weight during the first third of pregnancy was not affected by maternal undernutrition or overnutrition. On the other hand, undernutrition in the second and last third of gestation reduces the weight of the lamb both during pregnancy, at birth, and during the postnatal period, requiring at least 120 postnatal days to achieve the same weight as its contemporaries in the control treatment. However, this reduction in weight is not accompanied by reductions in morphometric measurements, demonstrating that the animals were lighter, but of equal size. In overnutrition, there is an increase in fetal weight in the second third of gestation. However, in the last third of the gestational period, there are no differences in fetal weight for the multiparous subgroup, but it was reduced in primiparous ewes. There are no effects of overnutrition on birth weight; however, this result is highly heterogeneous. Thus, maternal nutrition of ewe during pregnancy has effects on fetal and postnatal weight, but not on size. Furthermore, the effects of undernutrition are more homogeneous while overnutrition showed heterogeneous responses.

Gestational Exposure to Bisphenol A and Bisphenol S Leads to Fetal Skeletal Muscle Hypertrophy Independent of Sex

Gestational exposure to bisphenol A (BPA) can lead to offspring insulin resistance. However, despite the role that the skeletal muscle plays in glucose homeostasis, it remains unknown whether gestational exposure to BPA, or its analog bisphenol S (BPS), impairs skeletal muscle development. We hypothesized that gestational exposure to BPA or BPS will impair fetal muscle development and lead to muscle-specific insulin resistance. To test this, pregnant sheep (n = 7-8/group) were exposed to BPA or BPS from gestational day (GD) 30 to 100. At GD120, fetal skeletal muscle was harvested to evaluate fiber size, fiber type, and gene and protein expression related to myogenesis, fiber size, fiber type, and inflammation. Fetal primary myoblasts were isolated to evaluate proliferation and differentiation. In fetal skeletal muscle, myofibers were larger in BPA and BPS groups in both females and males. BPA females had higher MYH1 (reflective of type-IIX fast glycolytic fibers), whereas BPS females had higher MYH2 and MYH7, and higher myogenic regulatory factors (Myf5, MyoG, MyoD, and MRF4) mRNA expression. No differences were observed in males. Myoblast proliferation was not altered in gestationally BPA- or BPS-exposed myoblasts, but upon differentiation, area and diameter of myotubes were larger independent of sex. Females had larger myofibers and myotubes than males in all treatment groups. In conclusion, gestational exposure to BPA or BPS does not result in insulin resistance in fetal myoblasts but leads to fetal fiber hypertrophy in skeletal muscle independent of sex and alters fiber type distribution in a sex-specific manner.

Environmental epigenetics and epigenetic inheritance in domestic farm animals

Epigenetics refers to molecular factors and processes around DNA that can affect genome activity and gene expression independent of DNA sequence. Epigenetic mechanisms drive developmental processes and have also been shown to be tied to disease development. Many epigenetic studies have been done using plants, rodent, and human models, but fewer have focused on domestic livestock species. The goal of this review is to present current epigenetic findings in livestock species (cattle, pigs, sheep and poultry). Much of this research examined epigenetic effects following exposure to toxicants, nutritional changes or infectious disease in those animals directly exposed, or in the offspring they produced. A limited number of studies in domestic animals have examined epigenetic transgenerational inheritance in the absence of continued exposures. One example used a porcine model to investigate the effect that feeding males a diet supplemented with micronutrients had on liver DNA methylation and muscle mass in grand-offspring (the transgenerational F2 generation). Further research into how epigenetic mechanisms affect the health and production traits of domestic livestock and their offspring is important to elucidate.

Developmental Programming and Growth of Livestock Tissues for Meat Production

Maternal regulation of fetal development has consequences for growth and development of carcass tissues. Severely restricted fetal growth can reduce postnatal growth capacity, resulting in smaller-for-age animals that take longer to reach market weights but has little effect on feedlot efficiency or carcass and meat quality. Specific nutritional supplementation, particularly during later pregnancy, may limit fetal growth retardation and enhance postnatal growth capacity and carcass characteristics, and may improve development of intramuscular fat. Continued improvements in understanding developmental processes and their regulation will increase future capacity to improve growth, efficiency, carcasses, and meat quality through developmental programming.

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.

Maternal Restricted- and Over-Feeding During Gestation Result in Distinct Lipid and Amino Acid Metabolite Profiles in the Longissimus Muscle of the Offspring

Maternal over- and restricted-feeding during gestation have similar negative consequences for the offspring, including decreased muscularity, increased adiposity, and altered metabolism. Our objective was to determine the effects of poor maternal nutrition during gestation (over- and restricted-feeding) on the offspring muscle metabolite profile. Pregnant ewes (n = 47) were fed 60% (RES), 100% (CON), or 140% (OVER) of NRC requirements starting at day 30.2 ± 0.2 of gestation. Offspring sample collection occurred at days 90 and 135 of gestation, and within 24 h of birth. C2C12 myoblasts were cultured in serum collected from offspring at birth (n = 18; 6 offspring per treatment) for analysis of oxidative and glycolytic capacity. Unbiased metabolite analysis of longissimus muscle samples (n = 72; 8 fetuses per treatment per time point) was performed using mass spectrometry. Data were analyzed by ANOVA for main effects of treatment, time point, and their interaction. Cells cultured in serum from RES offspring exhibited increased proton leak 49% (p = 0.01) compared with CON, but no other variables of mitochondrial respiration or glycolytic function were altered. Mass spectrometry identified 612 metabolites. Principle component analysis identified day of gestation as the primary driver of metabolic change; however, maternal diet also altered the lipid and amino acid profiles in offspring. The abundance of 53 amino acid metabolites and 89 lipid metabolites was altered in RES compared with CON (p ≤ 0.05), including phospholipids, sphingolipids, and ceramides within the lipid metabolism pathway and metabolites involved in glutamate, histidine, and glutathione metabolism. Similarly, abundance of 63 amino acid metabolites and 70 lipid metabolites was altered in OVER compared with CON (p ≤ 0.05). These include metabolites involved in glutamate, histidine, lysine, and tryptophan metabolism and phosphatidylethanolamine, lysophospholipids, and fatty acids involved in lipid metabolism. Further, the amino acid and lipid profiles diverged between RES and OVER, with 69 amino acid and 118 lipid metabolites differing (p ≤ 0.05) between groups. Therefore, maternal diet affects metabolite abundance in offspring longissimus muscle, specifically metabolites involved in lipid and amino metabolism. These changes may impact post-natal skeletal muscle metabolism, possibly altering energy efficiency and long-term health.

Effects of Maternal Undernutrition during Mid-Gestation on the Yield, Quality and Composition of Kid Meat Under an Extensive Management System

Simple Summary

Nutrition status during pregnancy affects the meat production of offspring. In ruminants, the nutrient supply during the first and third periods of gestation is generally stressed, whereas the nutrition level during the second period of gestation is given less attention, in particular under the extensive husbandry system. This study focused on the effects of a 40% maternal undernutrition during mid-gestation, on the yield, quality, and composition of kid meat under an extensive system. The meat yield of the kids was decreased, while the meat quality and chemical composition, including the amino acid and fatty acid profiles, were unaffected. In meat production under an extensive husbandry system, the importance of the nutrient supply during mid-gestation in ruminants should be stressed.

Abstract

Nutritional status during mid-gestation is often ignored under extensive husbandry. This study aimed to examine the effect of maternal undernutrition during mid-gestation on kid meat production under an extensive system. Twenty-seven goats (45 ± 3 d of gestation) were randomly assigned to an unrestricted group (100% of nutrient requirements), or a restricted group (60% of nutrient requirements from 45 to 100 d of gestation, and then re-alimented to 100%). Among the offspring, 16 eligible kids (eight per treatment) were selected, based on birth type and survival, and were harvested to evaluate the meat yield, quality, and composition at 90 d after birth. Maternal undernutrition reduced the body weight and size, average daily gain and hot carcass weight of the kids (p < 0.05). The lightness of the meat at 45 min postmortem was increased (p = 0.029) in the restricted kids. Apart from an increase in tyrosine concentration (p = 0.046), the proximate composition and the amino acid and fatty acid profiles were unaffected in the restricted kids (p > 0.05). Overall, maternal undernutrition during mid-gestation decreased the yield of kid meat, but did not significantly modify the quality and composition. These results highlight the importance of nutrient status during mid-gestation in the meat production of small ruminants under an extensive regime.

Impact of energy restriction during late gestation on the muscle and blood transcriptome of beef calves after preconditioning

Background

Maternal nutrition has been highlighted as one of the main factors affecting intra-uterine environment. The increase in nutritional requirements by beef cows during late gestation can cause nutritional deficiency in the fetus and impact the fetal regulation of genes associated with myogenesis and immune response.

Methods

Forty days before the expected calving date, cows were assigned to one of two diets: 100% (control) or 70% (restricted group) of the daily energy requirement. Muscle samples were collected from 12 heifers and 12 steers, and blood samples were collected from 12 steers. The objective of this work was to identify and to assess the biological relevance of differentially expressed genes (DEG) in the skeletal muscle and blood of beef calves born from cows that experienced [or not] a 30% energy restriction during the last 40 days of gestation.

Results

A total of 160, 164, and 346 DEG (q-value< 0.05) were identified in the skeletal muscle for the effects of diet, sex, and diet-by-sex interaction, respectively. For blood, 452, 1392, and 155 DEG were identified for the effects of diet, time, and diet-by-time interaction, respectively. For skeletal muscle, results based on diet identified genes involved in muscle metabolism. In muscle, from the 10 most DEG down-regulated in the energy-restricted group (REST), we identified 5 genes associated with muscle metabolism and development: SLCO3A1, ATP6V0D1, SLC2A1, GPC4, and RASD2. In blood, among the 10 most DEG, we found genes related to response to stress up-regulated in the REST after weaning, such as SOD3 and INO80D, and to immune response down-regulated in the REST after vaccination, such as OASL, KLRF1, and LOC104968634.

Conclusion

In conclusion, maternal energy restriction during late gestation may limit the expression of genes in the muscle and increase expression in the blood of calves. In addition, enrichment analysis showed that a short-term maternal energy restriction during pregnancy affects the expression of genes related to energy metabolism and muscle contraction, and immunity and stress response in the blood. Therefore, alterations in the intra-uterine environment can modify prenatal development with lasting consequences to adult life.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5089-8) contains supplementary material, which is available to authorized users.

Off to the right start: how pregnancy and early life can determine future animal health and production

Animal producers are well aware that a low-birthweight animal is more likely to die in the first few days of life, and, if it survives, it is likely to perform poorly. We are now coming to appreciate that early life events can permanently change an animal’s developmental trajectory, also often referred to as developmental programming. This is an area of current interest in biomedicine, where the concept is known as the ‘developmental origins of health and disease’ (DOHaD). Current gaps in understanding include many of the underlying mechanisms, and whether and how we might intervene and restore the potential for healthy and productive development. This review introduces the biomedical perspective of developmental programming, reviews some of the evidence for long-term effects of early life exposures on welfare and productivity in animal production, with a focus on prenatal growth and maternal stress in pig production, and discusses options for intervening to improve long-term outcomes.

Programming Merino lambs by early feed restriction reduces growth rates and increases fat accretion during the fattening period with no effect on meat quality traits

The objective of the study was to determine the effect of early feed restriction on carcass and meat quality traits in Merino lambs. Twenty-four male Merino lambs (4.81±0.256kg) were assigned to two groups (12 animals in each group). The first group (ad libitum, ADL) was kept permanently with the dams. The second group (restricted, RES) was milk-restricted. After weaning (15kg), daily feed intake of all lambs was identical, but a lower gain: feed ratio was recorded in the RES group (0.320 vs. 0.261; P<0.001). After animals were slaughtered (27kg), lower ultimate pH and reduced yellow colouration of subcutaneous fat was recorded in meat from the RES lambs when compared to ADL group, whereas a trend towards a significant increment of intramuscular fat content and no effect on meat quality traits was observed in the RES lambs. Early feed restriction may be useful to increase intramuscular fat accretion in Merino lambs during the fattening period.

Differential effect of chronic undernutrition on the fiber type composition of fascicles in the extensor digitorum longus muscles of the rat

Several studies have shown that chronic low food consumption alters the composition and metabolism of the extensor digitorum longus muscle (EDLm) fiber types. EDLm is constituted by four independent fascicles (F2-F5) of different sizes; their constitution and metabolism, however, as well as how chronic undernourishment affects these is virtually unknown. Thus, the aim of this study is to evaluate the relative fiber type composition and metabolism of each independent fascicle in the EDLm, using control and chronically undernourished young male rats by using the alkaline ATPase and NADH-TR histochemical techniques. Our results indicate that all control fascicles showed a higher percentage of intermediate fibers (P<0.001), except for F5, which had a higher percentage of fast fibers (P<0.001). After chronic undernutrition, the proportion of intermediate fibers decreased in F4 (P<0.05) and increased in F5 (P<0.001), whereas fast fibers decreased in F3 (P<0.05) and F5 (P<0.001). When we investigated fiber metabolism we found that F3 and F4 had a similar composition (mainly glycolytic), whereas F2 and F5 predominantly contained oxidative fibers. All fascicles of chronic undernourished rats showed a general decrease in oxidative fibers (P>0.05), except for F3, in which oxidative fibers increased (P<0.05). After determining the possible predominant metabolism expressed in intermediate fibers, we propose that chronic undernutrition induces the transformation of fast-glycolytic to intermediate-oxidative/glycolytic fibers, mainly in F3 and F5. Our observations confirm that chronic undernourishment differentially affects the fiber types of each fascicle in the EDLm, which could alter their individual physiological contractile properties.

Fetal and organ development at gestational days 45, 90, 135 and at birth of lambs exposed to under- or over-nutrition during gestation,. Transl Anim Sci 2017;1:16-25. [PMID: 32704626 PMCID: PMC7235467 DOI: 10.2527/tas2016.0002]

To determine the effects of poor maternal nutrition on offspring body and organ growth during gestation, pregnant Western White-faced ewes (n = 82) were randomly assigned into a 3 × 4 factorial treatment structure at d 30.2 ± 0.2 of gestation (n = 5 to 7 ewes per treatment). Ewes were individually fed 100% (control), 60% (restricted) or 140% (over) of NRC requirements for TDN. Ewes were euthanized at d 45, 90 or 135 of gestation or underwent parturition (birth) and tissues were collected from the offspring (n = 10 to 15 offspring per treatment). Offspring from control, restricted and overfed ewes are referred to as CON, RES and OVER, respectively. Ewe data were analyzed as a completely randomized design and offspring data were analyzed as a split-plot design using PROC MIXED. Ewe BW did not differ at d 30 (P ≥ 0.43), however restricted ewes weighed less than overfed and overfed were heavier than controls at d 45, and restricted weighed less and overfed were heavier than controls at d 90 and 135 and birth (P ≤ 0.05). Ewe BCS was similar at d 30, 45 and 90 (P ≤ 0.07), however restricted ewes scored lower than control at d 135 and birth (P ≤ 0.05) and over ewes scored higher than control at d 135 (P ≤ 0.05) but not at birth (P = 0.06). A maternal diet by day of gestation interaction indicated that at birth the body weight (BW) of RES offspring was less than CON and OVER (P ≤ 0.04) and heart girth of RES was smaller than CON and OVER (P ≤ 0.004). There was no interaction of maternal diet and day of gestation on crown-rump, fetal, or nose occipital length, or orbit or umbilical diam. (P ≥ 0.31). A main effect of maternal diet indicated that the RES crown-rump length was shorter than CON and OVER (P ≤ 0.05). An interaction was observed for liver, kidney and renal fat (P ≤ 0.02). At d 45 the liver of RES offspring was larger than CON and OVER (P ≤ 0.002), but no differences observed at d 90, 135 or birth (P ≥ 0.07). At d 45, the kidneys of OVER offspring were larger than CON and RES (P ≤ 0.04), but no differences observed at d 90, 135 or birth (P ≥ 0.60). At d 135, OVER had more perirenal fat than CON and RES (P ≤ 0.03), and at birth RES had more perirenal fat than CON and OVER (P ≤ 0.04). There was no interaction observed for offspring heart weight, length or width, kidney length, adrenal gland weight, loin eye area or rib width (P ≥ 0.09). In conclusion, poor maternal nutrition differentially alters offspring body size and organ growth depending on the stage of gestation.

From Nutrient to MicroRNA: a Novel Insight into Cell Signaling Involved in Skeletal Muscle Development and Disease

Skeletal muscle is a remarkably complicated organ comprising many different cell types, and it plays an important role in lifelong metabolic health. Nutrients, as an external regulator, potently regulate skeletal muscle development through various internal regulatory factors, such as mammalian target of rapamycin (mTOR) and microRNAs (miRNAs). As a nutrient sensor, mTOR, integrates nutrient availability to regulate myogenesis and directly or indirectly influences microRNA expression. MiRNAs, a class of small non-coding RNAs mediating gene silencing, are implicated in myogenesis and muscle-related diseases. Meanwhile, growing evidence has emerged supporting the notion that the expression of myogenic miRNAs could be regulated by nutrients in an epigenetic mechanism. Therefore, this review presents a novel insight into the cell signaling network underlying nutrient-mTOR-miRNA pathway regulation of skeletal myogenesis and summarizes the epigenetic modifications in myogenic differentiation, which will provide valuable information for potential therapeutic intervention.

Epigenetics and developmental programming of welfare and production traits in farm animals

The concept that postnatal health and development can be influenced by events that occur in utero originated from epidemiological studies in humans supported by numerous mechanistic (including epigenetic) studies in a variety of model species. Referred to as the 'developmental origins of health and disease' or 'DOHaD' hypothesis, the primary focus of large-animal studies until quite recently had been biomedical. Attention has since turned towards traits of commercial importance in farm animals. Herein we review the evidence that prenatal risk factors, including suboptimal parental nutrition, gestational stress, exposure to environmental chemicals and advanced breeding technologies, can determine traits such as postnatal growth, feed efficiency, milk yield, carcass composition, animal welfare and reproductive potential. We consider the role of epigenetic and cytoplasmic mechanisms of inheritance, and discuss implications for livestock production and future research endeavours. We conclude that although the concept is proven for several traits, issues relating to effect size, and hence commercial importance, remain. Studies have also invariably been conducted under controlled experimental conditions, frequently assessing single risk factors, thereby limiting their translational value for livestock production. We propose concerted international research efforts that consider multiple, concurrent stressors to better represent effects of contemporary animal production systems.

Intrauterine growth-restricted sheep fetuses exhibit smaller hindlimb muscle fibers and lower proportions of insulin-sensitive Type I fibers near term

Intrauterine growth restriction (IUGR) reduces muscle mass and insulin sensitivity in offspring. Insulin sensitivity varies among muscle fiber types, with Type I fibers being most sensitive. Differences in fiber-type ratios are associated with insulin resistance in adults, and thus we hypothesized that near-term IUGR sheep fetuses exhibit reduced size and proportions of Type I fibers. Placental insufficiency-induced IUGR fetuses were ∼54% smaller (P < 0.05) than controls and exhibited hypoxemia and hypoglycemia, which contributed to 6.9-fold greater (P < 0.05) plasma norepinephrine and ∼53% lower (P < 0.05) plasma insulin concentrations. IUGR semitendinosus muscles contained less (P < 0.05) myosin heavy chain-I protein (MyHC-I) and proportionally fewer (P < 0.05) Type I and Type I/IIa fibers than controls, but MyHC-II protein concentrations, Type II fibers, and Type IIx fibers were not different. IUGR biceps femoris muscles exhibited similar albeit less dramatic differences in fiber type proportions. Type I and IIa fibers are more responsive to adrenergic and insulin regulation than Type IIx and may be more profoundly impaired by the high catecholamines and low insulin in our IUGR fetuses, leading to their proportional reduction. In both muscles, fibers of each type were uniformly smaller (P < 0.05) in IUGR fetuses than controls, which indicates that fiber hypertrophy is not dependent on type but rather on other factors such as myoblast differentiation or protein synthesis. Together, our findings show that IUGR fetal muscles develop smaller fibers and have proportionally fewer Type I fibers, which is indicative of developmental adaptations that may help explain the link between IUGR and adulthood insulin resistance.

The effect of maternal nutrition level during mid-gestation on postnatal muscle fibre composition and meat quality in lambs

Maternal nutrient intake during early- and mid-gestation can alter fetal growth and development with long-term consequences on the postnatal productivity and health of offspring. The aim of this study was to investigate the effects of maternal nutrition level during mid-gestation on postnatal growth rate, carcass composition, muscle fibre characteristics and meat quality in lambs. Ewes were fed from Days 30 to 80 of gestation as follows: 100% (control group, C), 50% (undernutrition, UN) or 175% (overnutrition, ON) of their daily requirement. During the rest of the gestation, the ewes in all groups were fed 100% of their daily requirements. Birth and weaning (at Day 90) weights of lambs born to ewes in nutritional groups were similar, but slaughter weights (at Day 150) and daily weight gain during finishing period of lambs born to the UN group were lower (P < 0.05). Similarly, a decrease in weights of semitendinosus (ST), semimembranosus and gastrocnemius muscles was observed in the lambs born to the UN group (P < 0.05). Lambs born to the ON group had a higher (P < 0.05) concentration of DNA in longissimus dorsi (LD) and ST muscles than UN groups, but they had a lower (P < 0.05) total protein and other proteins concentrations in LD and ST muscles than those to C and UN groups. Protein to DNA ratio in LD and ST muscles of lambs born to ON group were lower than those to C and UN groups (P < 0.05). However, lambs born to the ON group had a higher number of Type IIA and IIB muscle fibres in ST muscles but not in LD muscles than those in the C and UN groups (P < 0.05). Additionally an increase in the number of fibres/mm2 muscle area in lambs born to the ON group was observed in LD and ST muscles (P < 0.05). There were no significant differences between treatment groups in terms of meat quality parameters studied. This study confirms that maternal nutrition level during mid-gestation alters the postnatal growth and muscle fibre development of lambs.

Histochemical muscle fibre characteristics of German Heath lamb meat

Histochemical characteristics of muscle were evaluated in 12 German Heath lambs (6 males and 6 females). The lambs were slaughtered at the age of 150 days and samples of musculus longissimus lumborum et thoracis and quadriceps femoris were collected and measurements of fibre cross sectional area (µm2), diameter (µm2), and perimeter (µm2) were performed. Subsequently the fibre type distribution (%) was calculated. The dataset was evaluated using SAS 9.3. Significantly higher (P < 0.05) cross sectional area, diameter, and perimeter attributes were observed in females compared to males. Significant differences (P < 0.05 to 0.01) were observed in fibre type distribution between musculus longissimus lumborum et thoracis and quadriceps femoris muscle. The presented study describes evaluation of morphological formation of skeletal muscle tissue performed on a sheep breed of German origin. The results may be useful for meat scientists or meat industry due to close connection of these characteristics to meat quality.

Effects of gestational maternal undernutrition on growth, carcass composition and meat quality of rabbit offspring

An experiment was conducted in order to evaluate the effects of gestational undernutrition of rabbit does on growth, carcass composition and meat quality of the offsprings. Thirty primiparous non lactating rabbit does were artificially inseminated and randomly divided in three treatment groups: Control (C; fed to 100% of maintenance requirements throughout gestation, n = 10), early undernourished (EU; fed to 50% of maintenance requirements during days 7–19 of gestation, n = 10) and late undernourished (LU; fed to 50% of maintenance requirements during days 20-27 of gestation, n = 10). During the 4^th week of the gestation period, LU does significantly lost weight compared to C and EU groups (P<0.05). At kindling, C does produced litters with higher proportions of stillborn kits (P<0.05) while the total litter size (alive and stillborn kits) was not different among groups (10.7, 12.8 and 12.7 kits in C, EU and LU groups, respectively). Kit birth weight tended to be lower in the LU group. During fattening, body weight and feed intake were not different among offsprings of the three experimental groups. Moreover, the maternal undernutrition did not have any impact on carcass composition of the offsprings in terms of carcass parts and internal organs weights as well as meat quality of L. lumborum muscle (pH24, colour, water holding capacity and shear values) at slaughter (70 days of age). Therefore, it can be concluded that the gestational undernutrition of the mother does not have detrimental effects on the productive and quality traits of the offsprings.

Epigenetics and transgenerational inheritance in domesticated farm animals

Epigenetics provides a molecular mechanism of inheritance that is not solely dependent on DNA sequence and that can account for non-Mendelian inheritance patterns. Epigenetic changes underlie many normal developmental processes, and can lead to disease development as well. While epigenetic effects have been studied in well-characterized rodent models, less research has been done using agriculturally important domestic animal species. This review will present the results of current epigenetic research using farm animal models (cattle, pigs, sheep and chickens). Much of the work has focused on the epigenetic effects that environmental exposures to toxicants, nutrients and infectious agents has on either the exposed animals themselves or on their direct offspring. Only one porcine study examined epigenetic transgenerational effects; namely the effect diet micronutrients fed to male pigs has on liver DNA methylation and muscle mass in grand-offspring (F2 generation). Healthy viable offspring are very important in the farm and husbandry industry and epigenetic differences can be associated with production traits. Therefore further epigenetic research into domestic animal health and how exposure to toxicants or nutritional changes affects future generations is imperative.

Poor maternal nutrition during gestation in sheep reduces circulating concentrations of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in offspring

To determine if poor maternal nutrition alters growth, body composition, circulating growth factors, and expression of genes involved in the development of muscle and adipose of offspring, 24 Dorset and Shropshire ewes were fed either 100% (control fed), 60% (restricted fed), or 126% (over fed) of National Research Council requirements. Diets began at day 116 ± 6 of gestation until parturition. At parturition, 1 lamb from each control fed (CON), restricted fed (RES), and over fed (OVER) ewe was necropsied within 24 h of birth (1 d; n = 3/treatment) or reared on a control diet for 3 mo (CON = 5, RES = 5, and OVER = 3/treatment) and then euthanized. Body weights and blood samples were collected from lambs from 1 d to 3 mo. Organ weights, back fat thickness, loin eye area, and tissue samples (quadriceps, adipose, and liver) were collected at 1 d and 3 mo of age. The RES lambs weighed 16% less than CON (P = 0.01) between 1 d and 3 mo of age. In RES, there was a tendency for reduced heart girth at 1 d and 3 mo (P < 0.07) and back fat was reduced 36% at 3 mo (P = 0.03). Heart weight was 30% greater in OVER at 1 d when compared with RES lambs (P = 0.02). Serum IGF-I and IGFBP-3 were reduced in RES and OVER lambs (P < 0.05). Leptin tended to be greater in OVER lambs compared with CON at 1 d and 3 mo (P ≤ 0.08). Triiodothyronine was reduced in RES at 1 d (P = 0.05) and triglycerides tended to be greater in OVER at 3 mo (P = 0.07). In liver, there was a tendency for increased expression of IGF-I in OVER (P = 0.06) and decreased IGFBP-3 in RES (P = 0.09) compared with CON lambs at 1 d. In adipose tissue, adiponectin expression was decreased in RES (P = 0.05) at 3 mo. At 1 d of age, muscle expression of IGF-I tended to increase in RES (P = 0.06). In conclusion, poor maternal nutrition during gestation reduced growth rate in offspring which may be because of reduced circulating IGF-I and IGFBP-3 and decreased expression of IGFBP-3 in the liver.

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.

Impact of maternal dietary fat supplementation during gestation upon skeletal muscle in neonatal pigs

BACKGROUND

Maternal diet during pregnancy can modulate skeletal muscle development of the offspring. Previous studies in pigs have indicated that a fat supplemented diet during pregnancy can improve piglet outcome, however, this is in contrast to human studies suggesting adverse effects of saturated fats during pregnancy. This study aimed to investigate the impact of a fat supplemented (palm oil) "high fat" diet on skeletal muscle development in a porcine model. Histological and metabolic features of the biceps femoris muscle obtained from 7-day-old piglets born to sows assigned to either a commercial (C, n = 7) or to an isocaloric fat supplementation diet ("high fat" HF, n = 7) during pregnancy were assessed.

RESULTS

Offspring exposed to a maternal HF diet demonstrated enhanced muscular development, reflected by an increase in fractional growth rate, rise in myofibre cross-sectional area, increased storage of glycogen and reduction in lipid staining of myofibres. Although both groups had similar intramuscular protein and triglyceride concentrations, the offspring born to HF mothers had a higher proportion of arachidonic acid (C20:4n6) and a reduction in α-linolenic acid (C18:3n3) compared to C group offspring. The HF group muscle also exhibited a higher ratio of C20:3n6 to C20:4n6 and total n-6 to n-3 in conjunction with up-regulation of genes associated with free fatty acid uptake and biogenesis.

CONCLUSION

In conclusion, a HF gestational diet accelerates the maturation of offspring biceps femoris muscle, reflected in increased glycolytic metabolism and fibre cross sectional area, differences accompanied with a potential resetting of myofibre nutrient uptake.

Myoblasts from intrauterine growth-restricted sheep fetuses exhibit intrinsic deficiencies in proliferation that contribute to smaller semitendinosus myofibres

Intrauterine growth restriction (IUGR) reduces skeletal muscle mass in fetuses and offspring. Our objective was to determine whether myoblast dysfunction due to intrinsic cellular deficiencies or serum factors reduces myofibre hypertrophy in IUGR fetal sheep. At 134 days, IUGR fetuses weighed 67% less (P < 0.05) than controls and had smaller (P < 0.05) carcasses and semitendinosus myofibre areas. IUGR semitendinosus muscles had similar percentages of pax7-positive nuclei and pax7 mRNA but lower (P < 0.05) percentages of myogenin-positive nuclei (7 ± 2% and 13 ± 2%), less myoD and myogenin mRNA, and fewer (P < 0.05) proliferating myoblasts (PNCA-positive-pax7-positive) than controls (44 ± 2% vs. 52 ± 1%). Primary myoblasts were isolated from hindlimb muscles, and after 3 days in growth media (20% fetal bovine serum, FBS), myoblasts from IUGR fetuses had 34% fewer (P < 0.05) myoD-positive cells than controls and replicated 20% less (P < 0.05) during a 2 h BrdU pulse. IUGR myoblasts also replicated less (P < 0.05) than controls during a BrdU pulse after 3 days in media containing 10% control or IUGR fetal sheep serum (FSS). Both myoblast types replicated less (P < 0.05) with IUGR FSS-supplemented media compared to control FSS-supplemented media. In differentiation-promoting media (2% FBS), IUGR and control myoblasts had similar percentages of myogenin-positive nuclei after 5 days and formed similar-sized myotubes after 7 days. We conclude that intrinsic cellular deficiencies in IUGR myoblasts and factors in IUGR serum diminish myoblast proliferation and myofibre size in IUGR fetuses, but intrinsic myoblast deficiencies do not affect differentiation. Furthermore, the persistent reduction in IUGR myoblast replication shows adaptive deficiencies that explain poor muscle growth in IUGR newborn offspring.

Identification of the crucial molecular events during the large-scale myoblast fusion in sheep

It is well known that in sheep most myofibers are formed before birth; however, the crucial myogenic stage and the cellular and molecular mechanisms underpinning phenotypic variation of fetal muscle development remain to be ascertained. We used histological, microarray, and quantitative real-time PCR (qPCR) methods to examine the developmental characteristics of fetal muscle at 70, 85, 100, 120, and 135 days of gestation in sheep. We show that day 100 is an important checkpoint for change in muscle transcriptome and histomorphology in fetal sheep and that the period of 85–100 days is the vital developmental stage for large-scale myoblast fusion. Furthermore, we identified the cis-regulatory motifs for E2F1 or MEF2A in a list of decreasingly or increasingly expressed genes between 85 and 100 days, respectively. Further analysis demonstrated that the mRNA and phosphorylated protein levels of E2F1 and MEF2A significantly declined with myogenic progression in vivo and in vitro. qRT-PCR analysis indicated that PI3K and FST, as targets of E2F1, may be involved in myoblast differentiation and fusion and that downregulation of MEF2A contributes to transition of myofiber types by differential regulation of the target genes involved at the stage of 85–100 days. We clarify for the first time the timing of myofiber proliferation and development during gestation in sheep, which would be beneficial to meat sheep production. Our findings present a repertoire of gene expression in muscle during large-scale myoblast fusion at transcriptome-wide level, which contributes to elucidate the regulatory network of myogenic differentiation.