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Consumption of ergot alkaloids during the second half of gestation has been shown to decrease umbilical artery vasoactivity resulting in decreased birth weights. Negative vascular effects of ergot alkaloids are mediated predominantly through serotonergic and adrenergic receptors in other tissues. Vasoactivity of serotonin (5-HT) receptors 5-HT2A and 5-HT1B/1D in umbilical artery and vein from ewes receiving endophyte-infected seed (E + 1.77 mg ergovaline/hd/d) or a control total mixed ration (CON; 0 mg ergovaline/hd/d) tall fescue seed at d-110 and d-133 of gestation was evaluated. Gravid reproduction tracts were collected from ewes. Two-mm sections of umbilical artery and vein were exposed to increasing concentrations of a 5-HT1B/1D agonist and 5-HT2A agonist. The 5-HT1B/1D agonist did not stimulate a contractile response in artery or vein or either gestation time point. 5-HT2A agonist caused large responses in artery with greatest occurring at d-110 and decreasing in magnitude as days of gestation increased (p < 0.05). On d-110 and 133 of gestation, arteries from CON ewes had greater contractile response than arteries collected from E+ ewes (p < 0.05). Veins responded to increasing concentrations of the 5-HT2A agonist. Maximal d-110 vein response was greater than d-133 when exposed to 5-HT2A agonist (p < 0.05). Unlike the artery, veins from E+ ewes had greater d-133 contractile response than CON (p < 0.05). Vascular contractions of umbilical artery and vein are induced by 5-HT2A receptor activity and not 5-HT1B/1D. Umbilical artery 5-HT2A receptor activity was more sensitive to seed treatment and could be responsible for ergot alkaloid-induced intra-uterine growth restriction. [ABSTRACT FROM AUTHOR]

microRNAs (miRNA) are small non-coding RNAs that modulate muscle satellite cell proliferation. Previous research identified miR-22-3p as differentially expressed during ovine muscle development and in vitro experiments showed that antagomir-22-3p treatment enhanced satellite cell proliferation. The objective of this study was to test in vivo vascular injection of antagomir-22-3p in lateral saphenous vein on miRNA and HDAC family mRNA expression in intrauterine growth restricted lambs. Pregnant ewes (n = 18) with twins were either fed at 100% of NRC (CON) or nutrient restricted (60% NRC; NR) from gestational d 85 to parturition. On d 12 of age, NR lambs (n = 8) were randomly selected and given a systemic injection of antagomir-22-3p in the lateral saphenous vein of the right leg (MIR-NR). CON lambs (n = 8) were also randomly selected and given a sham injection of PBS in the lateral saphenous vein of the right leg (SHAM-CON). Antagomir-22-3p was reconstituted in phosphate buffered saline (PBS). Injections were given for 3 consecutive days and lambs harvested 24 d later. Blood samples were collected from each lamb weekly to monitor miR22-3p expression. Lambs were slaughtered 24 d after the first injection and muscle mass measured. Muscle samples were removed for miR-22-3p and mRNA expression of potential targets. Cell-free circulating RNA was isolated from blood samples and miR-22-3p expression examined over time. Cell-free circulating miR22-3p expression was downregulated (P < 0.05) for MIR-NR compared with SHAM-CON on d 14 after injection. On d 21 after injection, miR-22-3p expression in plasma tended (P = 0.08) to be down-regulated in MIR-NR compared with SHAM-CON. Lamb body weight and muscle weights at harvest were similar between MIR-NR and SHAM-CON treatments. In heart and semimembranosus (SM) muscles, expression of miR-22-3p was down-regulated (P < 0.05) in MIR-NR compared with SHAM-CON. In the gastrocnemius and semitendinosus muscle, miR-22-3p expression was unchanged (P > 0.05). The number of type I and IIa muscle fibers were greater (P < 0.05) for MIR-NR than SHAM-CON. Muscle fiber area of Type I, IIa or IIx fibers did not differ (P > 0.05) by treatment. The number of type IIx fibers did not differ (P > 0.05) between treatments. MIR-NR treatment appears to shift muscle fibers towards more oxidative metabolism and down-regulate HDAC-1, 3, and 11 and SIRT6 in SM. The systemic injection of antagomir-22-3P downregulated miR-22-3p expression in circulation and in muscle tissues, which altered expression of HDAC/ SIRT genes involved in muscle fiber type conversion and hypertrophy [ABSTRACT FROM AUTHOR]

microRNAs (miRNA) are present in skeletal muscle and play important roles in regulating gene expression. Previous research identified miR-22-3p and miR-127 as differentially regulated during muscle hypertrophy and in vitro experiments found that antagomir-22-3p and mimic-127 enhanced satellite cell proliferation. The objective of this study was to test in vivo intramuscular injection of agomiR-127 or antagomir-22-3p in the longissimus muscle (LM) on miRNA and target mRNA expression in intrauterine growth restricted lambs. Pregnant ewes (n = 18) with twins were nutrient restricted (60%) from gestational d 85 to parturition. On d 2 of age, lambs were randomly selected and assigned to one of two miRNA treatments, 1) agomiR-127 (AGO127, 100 nM, n = 9) to assess gain of function or 2) antagomiR-22-3p (ANT22, 500 nM, n = 9) to assess loss of function. AgomiR and antagomiR technologies are chemically modified miRNA mimics or inhibitors that do not require transfection for in vivo use. AgomiR-127 or antagomir-22-3p were reconstituted in phosphate buffered saline (PBS) and injected into the center of the LM on the left side every 3-d starting at the 10th rib and moving posterior by 1.27 cm at each injection for a total of 7 injections. A sham control treatment (SHAM127 or SHAM22) of PBS was administered following the same protocol in the right LM to serve as the in-animal control. Lambs were harvested 4 d after the last injection and samples were collected from the injection region of each LM for miRNA and mRNA expression, histology, and proteomic analyses. Data were analyzed using paired t-tests to compare each miRNA treatment to its SHAM within animal. AGO127 up-regulated (P = 0.0071) miR-127 expression compared with SHAM127. mRNA expression of PAX7 and MSTN were up-regulated (P < 0.05) and IGFBP2 expression was down-regulated (P < 0.05) for AGO127 compared with SHAM127. Both protein and DNA content of AGO127 were increased (P < 0.05) but the ratio of protein to DNA did not change (P > 0.05). Proteomic analyses found 11 proteins that were differentially expressed for AGO127 compared with SHAM127. ANT22 down-regulated (P = 0.0024) miR-22-3p expression from SHAM22. Expression of predicted mRNA targets of miR-22-3p (ACVR2a, ACVR2b, SIRT1), myosin heavy chain isoforms (MyHCI, MyHCIIa, MyHCIIx), and other myogenic genes (MAPK6, IGF1, MyoG) were also altered (P < 0.05) in the LM compared with SHAM22. DNA content and the protein to DNA ratio was greater (P < 0.05) in ANT22 than SHAM22. Proteomic analyses identified nine proteins that were differentially expressed (P < 0.05) for ANT22. The direct injection of agomiR and antagomir technologies in the LM up- and downregulated expression, respectively, for the miRNA of interest, which altered mRNA expression of predicted targets, protein abundance and muscle fiber type. [ABSTRACT FROM AUTHOR]

Herbivores that consume ergot alkaloids frequently suffer from vasoconstriction that can result in a myriad of symptoms that can range from necrosis of peripheral tissues to fetal intra-uterine growth restriction. As part of a larger study screening compounds that may mitigate the vasoconstrictive effects of ergot alkaloids, the objective of this experiment was to evaluate serotonin (5-HT) as vasorelaxant in the ovine saphenous artery and vein. Blood vessels were collected from a total mixed breed market rams (n = 16; approximate BW = 58 kg) at slaughter, cleaned of surrounding adipose and connective tissue, sliced into 2-mm crosssections, and mounted in a multimyograph. Artery and vein cross-sections were equilibrated to 1 g tension in continuously gassed (95% O2/5% CO2) Krebs-Henseleit buffer (pH 7.4; 37.5 °C) for 90 min, precontracted with 0.0001 M phenylephrine for 15 min, exposed to concentrations of 5-HT that ranged from 1 x 10-9 to 1 x 10-4 M for a 5-min interval. Response data were normalized to the 0.0001 M phenylephrine response and were analyzed as a completely randomized design in SAS. The lateral saphenous vein (n = 5 lambs) relaxed to increasing concentrations of 5-HT (P < 0.05) with 65 to 75 % relaxation occurring at 1 x 10-7 M through 1 x 10-4 5-HT. Conversely, the lateral saphenous artery (n = 6 lambs) contracted in response to increasing concentrations of 5-HT (P < 0.05) resulting in a 255% increase from the phenylephrine response by the 1 x 10-4 M addition. In a subsequent experiment, saphenous veins from the remaining lambs (n = 5) were treated the same, but in place of increasing concentrations of 5-HT, saphenous veins were exposed to increasing concentrations of selective 5-HT receptor agonists to determine the receptor subtypes involved in the previously observed vasorelaxation. Agonists for receptors 5-HT2B (BW 723C86; a-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine hydrochloride), 5-HT4 (BIMU-8; 2,3-Dihydro-N-[(3-endo)-8-methyl-8-azabicyclo[3.2.1]oct-3-yl]-3-(1-methylethyl)-2-oxo-1Hbenzimidazole-1-carboxamide hydrochloride), and 5-HT7 (LP44; 4-[2-(methylthio)phenyl]-N-(1,2,3,4-tetrahydro-1-naphthalenyl)-1-piperazinehexanamide, monohydrochloride) were used. These 5-HT receptor subtypes were selected based on their association with vascular smooth muscle relaxation. While all three 5-HT receptor subtypes resulted in vasorelaxation (P < 0.05), the 5-HT2B agonist only stimulated a maximal relaxation of 32% compared with the agonists for 5-HT4 and 5-HT7 that resulted in maximal relaxation of 68% and 50%, respectively. The agonist for 5-HT4 produced the greatest relaxation in the ovine lateral saphenous vein and should be targeted in subsequent research. It is likely that the combined effect of binding multiple receptor subtypes contributes to the overall effect of 5-HT. The focus on development of ergot alkaloid mitigation strategies should consider the divergent responses of arteries and veins to serotonin in peripheral tissues. [ABSTRACT FROM AUTHOR]

Mentored undergraduate research experiences have been identified as beneficial to students for persistence in STEM disciplines and increased grade point averages. Participation in research is impactful for both STEM and non-STEM students. Additionally, undergraduate research experiences have a positive effect on subsequent student performance in graduate and professional school as evidenced by students with previous research experience having superior communication skills at the start of their first year and after. Undergraduate research courses tend to be heavily hands-on experiences and structured classroom teaching may not be large portions of the course content. Online material has become increasingly common in the post COVID-19 learning environment. Courses that can have difficulty with online instruction or the inclusion of online content tend to be courses with a heavy focus of hands-on learning or hands-on skill development. The use of a flipped classroom can facilitate student learning in a digital way in addition to in person class meeting. The incorporation of online lecture content to broaden undergraduate student understanding of the application of the scientific method was used to enhance the research experience. Student experiences were evaluated with the Undergraduate Research Student Self-Assessment survey. Significant positive correlation was found between student feelings of "project responsibility" and "Workshops on science writing and presentation" during the semester that online lectures were incorporated. Additionally, graduate student training is a variable and highly individualized experience for each trainee. Most programs focus strongly on cognitive skill training, advanced knowledge of the discipline, conducting research, and preparing manuscripts for publication. Professional development is a component of graduate training that can be easily overlooked or undervalued. The development of soft skills such as time management, personnel management, and leadership and mentoring qualities are vital for trainee success post-graduation. Some current thinking is that devoting time to professional development will result in a slower progression by the trainee, however this is shown to be untrue and students who participate in career growth maintained the same level of productivity measured by time to degree completion and manuscript output. Graduate student experiences with mentoring undergraduates were shown to develop soft skills while also being noted as "an influential experience" when making future career decisions. Development of an undergraduate research program that incorporates more than simply hands on skill development that also significantly incorporates graduate students benefits both student groups and leads to improved outcomes for both student groups post-graduation. [ABSTRACT FROM AUTHOR]

The Texel breed is a double muscled breed of sheep that is commonly used as a terminal sire in meatproduction. The increase in muscle mass is related to a single nucleotide polymorphism in the myostatin gene, a myokine that inhibits muscle growth. There is limited information on how postnatal skeletal muscle fiber hypertrophy is altered in Texel lambs. Satellite cells or muscle stem cells have a major role in postnatal hypertrophy of muscle fibers. Satellite cells are generally found in a state of quiescence and must activate, proliferate, and differentiate to increase DNA content in myofibers during periods of postnatal muscle growth. The objective of this study was to evaluate muscle fiber hypertrophy and satellite cell proliferation and differentiation in lambs of two sire breeds, Texel or Suffolk. Male lambs of each sire breed (n = 4/sire breed/time) were harvested at d 2, 14, and 203 of age. Muscle samples were collected from the longissimus and snap frozen for examination of myofiber cross-sectional area by fluorescent immunohistochemistry. Another portion of the longissimus was used to isolate satellite cells for in vitro experiments to examine population number, proliferation, and differentiation capacity. Isolated satellite cells were counted, seeded for activation, and grown until colonies reached 80% confluence. Activated cells were seeded for a proliferation assay measuring DNA content daily for 6 days. Following proliferation, cells were differentiated for 4 days, and the number of differentiated nuclei were counted with fluorescent immunohistochemistry. Sire breed did not impact (P < 0.05) the weight of the longissimus; however, muscle ribeye area tended (P < 0.10) to be increased for Texel lambs compared with Suffolk lambs. In the early postnatal period, from d 2 to 14, longissimus mass increased (P < 0.05) by 160%, and ribeye area increased by 100%. Between d 4 and 203 longissimus mass increased (P < 0.05) by 350%, while longissimus area only increased by 100%. Muscle fiber cross sectional area expanded (P < 0.05) from d 14 to 203 of age, and cross-sectional area was greater (P < 0.05) for Texel than Suffolk lambs at d 203. Satellite cell populations per gram of tissue increased (P < 0.05) between d 2 and 14 and decreased from d 14 to 203. The number of satellite cells that activated from quiescence was reduced (P < 0.05) as animal age increased but was not impacted (P > 0.05) by sire breed. Following activation, satellite cell proliferation capacity was greater (P < 0.05) for Texel compared with Suffolk satellite cells. Differentiation capacity was not altered (P > 0.05) by sire breed. Texel-sired lambs had larger longissimus cross-sectional muscle fiber area at d 203 of age than Suffolk. These changes appear to be related to greater proliferation of satellite cells, the stem cells of muscle, to enhance muscle fiber hypertrophy during postnatal growth. [ABSTRACT FROM AUTHOR]

Backgrounding or stocker operations attempt to add value to calves by efficiently adding weight and predominately taking advantage of the protein accretion phase of development, ultimately preparing calves for later stages of production. The objective of the current study was to evaluate the effects of an implant (Revalor-G) or implant plus supplementation on protein accretion patterns in backgrounded beef steers. A 56-day backgrounding study was conducted using Angus-based steers (n = 69; initial BW 233 ± 29 kg) grazing a cow pea and millet mixture. Steers were randomly assigned to one of three treatments (n = 23 steers per treatment): 1) grazing only (G), 2) grazing with implant (GI), or 3) grazing with implant plus individual animal supplementation via Super Smart Feeder at 0.75% BW (GIS). Steers were weighed and blood was collected every 14 days to determine plasma blood urea nitrogen (BUN) and creatinine concentrations. Ultrasound measurements of ribeye area and backfat were collected at days 0, 28, and 56 of study. Data were analyzed using the GLIMMIX function of SAS version 9.4. GIS steers had a greater (P = 0.0004) body weight change than GI or G steers. GI and GIS steers had a greater (P = 0.0117) ribeye area compared with G steers. GI steers had a greater (P < 0.0180) ribeye area to body weight ratio than G steers. When evaluating blood parameters, GI steers had a greater (P< 0.0009) plasma BUN concentration than GIS steers. No treatment differences were observed for plasma creatinine concentrations. G and GI steers had a greater (P = 0.0290) BUN to creatinine ratio than GIS steers. Results of this study suggest that implanted steers may require additional supplementation to optimize growth and muscle accretion. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine how the use of specific miRNA mimics or inhibitors alters ovine satellite cell proliferation in vitro. Satellite cells were isolated from a Texel x Suffolk cross lamb at d 2 of age and cell purity was assessed with PAX7 protein staining and the population was 95% pure. miRNA candidates were selected from miRNA sequencing of the longissimus muscle at several time points from gestational d85 to market weight. Satellite cells were plated and allowed to reach 60% confluence, then treated with a miRNA mimic (miR-127 or 299a) at 50 or 100nM or a miRNA AntagomiR (miR-22-3p, 29a, 133, or 27) at 500nM using lipofectamine transfection reagent. Cells were allowed to proliferate for 4d following transfection and samples were collected daily for proliferation analysis using DNA quantification. Experiments were replicated and data analyzed using a priori contrasts with miRNA treatment in the model. DNA quantification showed that miR-127 mimic-100nM and miR-22-3p AntagomiR increased (P< 0.05) DNA content after 4d of proliferation following transfection. miR-127 mimic-100nM treatment increased (P< 0.05) miR-127 expression relative to controls at d1 and d4 post transfection. miR-22-3p AntagomiR transfection tended (P< 0.10) to reduce miR-22-3p expression on d4 post-transfection. miR-22-3p AntagomiR did not alter (P>0.05) PAX7, MYOD, or MYOG expression compared with the control. miR-127 mimic-100nM treatment did not alter (P>0.05) PAX7 expression, while it did increase (P< 0.05) MYOD expression on d4 and reduced (P< 0.05) MYOG expression compared to the control. mRNA sequencing was performed on d4 samples to determine possible miR-127 and 22-3p targets. IGF1, fibroin and other extra cellular matrix proteins were identified from miR-127 treated samples and CNDP2, involved in carnosine hydrolysis, was identified from miR-22-3p treated samples. miR-127 and 22-3p enhanced satellite cell proliferation and therefore could be used to promote muscle fiber hypertrophy. [ABSTRACT FROM AUTHOR]

Research has established that muscle fiber hyperplasia is complete during mid gestation; therefore, skeletal muscle fiber hypertrophy is responsible for the increase in muscle mass observed during late gestation and postnatal growth periods. Our research is investigating key times points during muscle fiber hypertrophy and the role of miRNA and mRNA transcriptome in this process. Two studies were conducted to examine changes in muscle mass, muscle fiber hypertrophy, and gene expression from gestational d (gd) 85 to market weight in Suffolk or Texel cross lambs. Longissimus muscle (LM) samples were taken for muscle fiber histology at the following time points: gd85, gd110, gd133, and market (d243) in study one and at postnatal d2, d14 and d203 in study two. microRNA (miRNA) and mRNA sequencing of the LM were conducted in study one and included biopsies at d 42 and 65. Type I and Type II muscle fiber area increased (P < 0.05) at each stage of growth evaluated. Type I muscle fiber area increased by 26.7-fold and Type II muscle fiber area increased by 37.4-fold from gd85 to market (d243). mRNA sequencing identified a total of 9360 unique genes differentially expressed (DEGs; P < 0.05) in LM during hypertrophic growth but the majority of DEGs were observed in the prenatal (51%) and early postnatal (54%) periods. There were 142 unique miRNAs differentially expressed (P < 0.05) during hypertrophic growth of LM but the majority (62%) were observed in the transition period from prenatal to postnatal growth. Overall, muscle fiber hypertrophy is dynamic from late gestation through postnatal growth, but transcriptomic changes indicate key time periods during development in which mechanisms underlying hypertrophic growth may be altered. [ABSTRACT FROM AUTHOR]

Consumption of ergot alkaloids during the second half of gestation have been shown to decrease umbilical artery vasoactivity resulting in lighter birth weights. The objective was to evaluate vasoactivity of serotonin (5HT) receptors 5HT2A and 5HT1B/1D in umbilical artery and vein from ewes receiving endophyteinfected (E+ 1.77 mg ergovaline/animal/day) or endophyte-free (E-; 0 mg ergovaline/animal/day) tall fescue seed at d-85 (n=4), 110 (n=4 E+; n=4 E-), 135 (n =4 E+; n=4 E-) of gestation. Suffolk ewes began receiving seed treatments on d-86 of gestation. Umbilical artery and vein were collected from ewes at slaughter. Two-mm blood vessel cross sections were mounted in multi-myographs containing Krebs-Henseleit buffer and exposed to increasing concentrations of rizatriptan benzoate (5HT1B/1D agonist) and TCB-2 (5HT2A agonist). Data were analyzed as a split-plot with mixed models of SAS. The 5HT1B/1D agonist did not stimulate a contractile response in either vessel for any gestation time point evaluated. The 5HT2A agonist caused contractile responses in umbilical artery with the greatest occurring at d-85 and decreasing in magnitude as days of gestation increased (P< 0.05). On d-110 and 133 of gestation, umbilical arteries from ewes receiving E-seed had a greater contractile response than those arteries collected from ewes receiving the E+ treatment (P< 0.05). Umbilical veins also responded to increasing concentrations of 5HT2A agonist and maximal response was not different between d-85 and 110 of gestation, but both were greater than d-133. Unlike the artery, umbilical veins from ewes receiving E+ seed had greater contractile response than E-at d-133 (P< 0.05). These results demonstrate that ovine vascular smooth muscle contractions of the umbilical artery and vein are induced by 5HT2A receptor activity and not 5HT1B/1D. Umbilical artery 5HT2A receptor activity responded to seed treatment differently than umbilical vein and could be the source of ergot alkaloid-induced intra-uterine growth restriction. [ABSTRACT FROM AUTHOR]

Excess fat deposition is costly to the producer in terms of input and final product; it also usually does not occur equally across all adipose depots. Further examination is necessary to determine a correlation between varying gene expression and fatty acid composition in different tissue depots, and further, across different breeds. Texel-Suffolk (n = 5) and Suffolk-Suffolk (n = 4) lambs were finished to 203 d of age and used to compare both mRNA and microRNA (miR) gene expression changes between breed and among tissue depots. Seven different depots were harvested and snap-frozen from all nine lambs. The liver, longissimus muscle of the rib, kidney fat, mesenteric fat, omental fat, subcutaneous fat, and intermuscular fat were all harvested. Texel-sired lambs had greater (P < 0.05) flank streaking, quality grade, and weight of fat depots compared to Suffolk. Texelcross lambs had higher (P < 0.05) oleic-to-stearic fatty acid ratio than Suffolk lambs in this study, displaying a breed difference concerning this desaturation ratio. Tissue and breed interactions were observed for oleicto-stearic and palmitoleic-to-palmitic ratio differences (P < 0.05) depending on tissue type. Tissue and breed interactions were trending in various tissues concerning the expression of the gene, stearoyl-CoA desaturase-1(SCD-1). SCD-1 seemed to be upregulated (P < 0.10) in a multitude of tissues while others do not appear to be differentially expressed, dependent upon breed. Data showed an association between SCD-1 and mi-199a-3p among different tissue variations. This may suggest that adipose tissue is more complex than what is currently known. Lipogenic gene expression differed between tissue and adipose depots, and could potentially broaden targets that could aid in maximizing animal efficiency. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the miRNA transcriptome and muscle fiber characteristics of lambs from ewes consuming endophyte-infected tall fescue (E+) seed during two stages of gestation at two animal ages. Pregnant Suffolk ewes (yr 1 n = 36; yr 2 n = 60) were randomly assigned to one of two gestational treatments: E+ seed (1.77 mg/hd/d of ergovaline/ergovalinine) during mid-(gd 35 - 85; MID) or lategestation (gd 86 - 133/parturition; LATE). Longissimus muscle samples (n = 3/E+ treatment/time) were collected from fetuses on gd 133 (FETAL; expt. 1) or from wethers after finishing to market weight (MKT; expt. 2) from ewes from MID and LATE E+ treatments. Data were analyzed as a 2 x 2 factorial with E+ treatment (MID or LATE), time (FETAL or MKT), and the two-way interaction in the model. Exposure to E+ fescue seed during LATE gestation reduced (P = 0.03) cross-sectional area of Type II muscle fibers at MKT but not at FETAL. Cross-sectional area of Type II muscle fibers were larger (P < 0.05) at MKT than FETAL. Animal age influenced miRNA expression with 120 miRNA differentially expressed. miRNA-22-3p and -29a were down regulated (P < 0.001; > -5 log fold change) with animal age; whereas miR-3958-3p, -410-3p, -299-5p and -487b-3p (P < 0.0001; > 3 log fold change) were up-regulated. Exposure to E+ during MID or LATE gestation did not alter miRNA expression. Muscle fiber hypertrophy increased from FETAL to MKT age altered the expression of miRNA in longissimus muscle. [ABSTRACT FROM AUTHOR]

Suffolk ewes (n = 26) were blocked by body condition and weight, and randomly divided into two breeding groups (n = 13/group). One group was bred to a Texel ram and the other to a Suffolk ram. Ewes were confirmed pregnant by ultrasound and went to term. Male lambs (n = 4/sire/time) were harvested on d 2, 14, and 203 of age for muscle characterization and satellite cell isolation. From d 2 to 14, body weight increased (P < 0.01) by 80%, weight of the longissimus increased by 160%, and longissimus muscle area increased by 100%. Between d 14 and 203 lamb weight and weight of the longissimus increased by 350%, while longissimus area only increased by 100%. Sire breed did not alter lamb weight or weight of the longissimus (P > 0.10). Longissimus muscle area tended (P < 0.10) to be increased for Texel sired lambs when compared to Suffolk sired lambs. The total number of satellite cells isolated were not different by sire breed but did differ by animal age (P < 0.01). Satellite cell populations per gram of tissue increased between d 2 and 14 and decreased from d 14 to 203. Due to the large changes in growth from d2 to 14, satellite cell proliferation was examined at d 2 of age. Satellite cell proliferation capacity was altered by sire breed at d 2 of age potentially contributing to the increased longissimus muscle area. Advancing animal age and development alters satellite cell population numbers and potentially supports a high capacity for growth. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the miRNA transcriptome of the longissimus muscle during skeletal muscle hypertrophy. Longissimus samples were collected from Suffolk x Texel cross sheep at six developmental time points: Prenatal [gd 85 (PN1), 110 (PN2), and 133 (PN3)] and postnatal [preweaning (d 40; PW1), weaning (d 65; PW2), and maturity (57 kg; MKT)]. Total RNA was extracted for miRNA sequencing. Data were analyzed using a priori comparisons PN1 vs. PN2, PN2 vs. PN3, PN3 vs. PW1, PW1 vs. PW2, PW2 vs. MKT to examine stages of muscle hypertrophy. One hundred forty-two miRNAs were differentially expressed between the 5 comparisons made. The stage from PN3 to PW1 had the most differentially expressed miRNA (115). Examination of the differentially expressed miRNA also showed that 4 miRNA, miR-154a-3p, miR-3956-5p, miR-410-3p, and miR-431, had a log fold change greater than 3 and miR-22-3p had a log fold change greater than 4. Target genes of differentially expressed miRNA were identified and the functional associations of genes were assessed with GOseq. Between all 5 comparisons made, 195 terms were significantly enriched, 86 were from biological process, 42 were from cellular component, and 67 were from molecular function. The miRNA transcriptome of skeletal muscle changes with advancing development and the period from gd133 to d40 appears to have increased transcriptome alteration. [ABSTRACT FROM AUTHOR]

There is increased competition in the protein market with the entrance of cell-based and plant-based products. Consumers issues with consumption of red meat typically center around saturated (SFA) fatty acid content and environmental impacts associated with production. Nutritional system used for finishing beef and lamb alters fatty acid composition of the meat product. Forages and grasses that are utilized in a grass-fed finishing system increases the animal's intake of a-linolenic acid (C18:3 n-3), the main fatty acid present in plants (57%) that can be converted to eicosapentaenoic (C20:5 n-3), docosapentaenoic (C22:5 n-3) and docosahexaenoic (C22:6 n-3) acids in animal tissues. Grain-fed finishing systems increases the animal's intake of linoleic acid (C18:2 n-6), the main fatty acid present in corn grain (57%), that can be converted to arachidonic acid (C20:4 n-6) and docosatetraenoic acid (C22:4 n-6) in animal tissues. Biohydrogenation of polyunsaturated fatty acids (PUFA) is extensive in the rumen (> 80% of dietary PUFA) and rumen protected supplements are needed to enhance PUFA content of ruminant meat products. Saturated (SFA) and monounsaturated (MUFA) fatty acids are the majority (>75% of total fatty acids) of fatty acids present in ruminant meat products. Therefore, finding approaches to attain greater desaturation of palmitic and stearic acids to their MUFA products, palmitoleic and oleic acids, would be most beneficial. The content of oleic acid and MUFA in beef is highly heritable and some breeds have high levels of MUFA. Stearoyl-CoA desaturase (SCD1) is the rate limiting enzyme in the production of MUFA. More research is needed to find ways of altering SCD1 expression in meat animal tissues to enhance MUFA and lower SFA content. [ABSTRACT FROM AUTHOR]