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Perturbations of the prenatal environment may influence fetal muscle development. This study investigated muscle cellularity and mRNA abundance of myogenic genes in fetal sheep divergent in their patterns of growth. Muscle samples were obtained from small and large fetuses on Days 50, 92 and 133 of pregnancy. Number of myofibres in the semitendinosus muscle increased between Day 92 and 133 of pregnancy, but did not differ between small and large fetuses at either stage of pregnancy. The semitendinosus of small fetuses had smaller cross-sectional areas of myofibres than did those of their large counterparts on Day 133 of pregnancy. The semitendinosus of small fetuses also had lower DNA concentration on Day 92 and lower protein concentration on Day 133 than did those of large fetuses. The mRNA levels of the myogenic regulatory factors (MRFs), myostatin, the insulin-like growth factors and embryonic myosin in fetal muscles varied with the stage of development, but no differences occurred in response to divergent fetal growth. Myostatin mRNA was more abundant in the semitendinosus than in the supraspinatus muscle on Days 92 and 133, as were myogenic regulatory factors, myf-5, myf-6 andfollistatin mRNA on Day 133. The results indicated that muscle growth but not the number of myofibres in fetal sheep is modified by restricted fetal growth, and that genes that regulate muscle development are affected by the stage of development in an anatomical muscle-specific manner. [ABSTRACT FROM AUTHOR]

The objective of this study was to inves-tigate whether single nucleotide polymorphisms (SNP) in the calpain 1 {CAPNI), calpain 3 {CAPN3) and cal-pastatin (CAST) genes, which have been shown to be associated with shear force and tenderness differences in the skeletal muscle of cattle, contribute to pheno-typic variation in muscle tenderness by modulating the transcriptional activity of their respective gene. The mRNA expression of the calpain and CAST genes was assessed in the longissimus lumborum muscle (LLM) of cattle from two herds located in distinct production zones on the east (New South Wales, NSW) and west (Western Australia, WA) of Australia. The cattle in the herds were mainly Brahman cattle {Bos indicus) with smaller populations of Angus cattle {Bos taurus). There were 191 steers in the WA herd and 107 steers and 106 heifers in the NSW herd. These herds were established by choosing cattle from the diverse population which had different single nucleotide polymorphism (SNP) genotypes at the CAPNI, CAPN3 and CAST loci. Using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), the transcriptional activities of the CAPNI and the CAST genes, but not the CAPN3 gene, were found to differ between favorable, positively associated with tenderness, and unfavorable, negative-ly associated with tenderness, allelic variants of these genes. These findings suggest that the muscle shear force and consumer taste panel differences in tender-ness explained by the CAPNI and CAST gene markers are a consequence of alterations in their mRNA levels, which may ultimately influence the protein activity of these genes, thereby altering the rate and(or) the extent of postmortem proteolysis in skeletal muscle. Of partic-ular importance were the significantly lower type II and type III CAST 5' splice variant mRNA levels that were detected in the LLM muscle of Brahman and Angus cattle with 2 favourable alleles of the CAST:c.2832A > G polymorphism. Moreover, a reduction in the abun-dance of an alternative polyadenylated variant of the CAST transcript, terminated at the proximal polyade-nylation site, provides a unique insight into the potential involvement of a post-transcriptional regulatory mech-anism which may influence protein expression levels in bovine skeletal muscle. [ABSTRACT FROM AUTHOR]

The economically important characteristics of the adult fleece of Merino sheep, such as increases in clean fleece weight, fibre length, fibre diameter and crimp characteristics are determined during critical phases of fetal development of the skin and its appendages. Genetics plays a major role in the development of traits, but the maternal uterine environment could also influence development. Treatment of pregnant ewes with cortisol and its analogues has previously been shown to produce changes in wool follicle morphology. The aim of this study was to determine the effect of transient manipulation of maternal cortisol status during critical phases of wool follicle initiation and development in utero. From Days 55-65 post-conception, singleton-bearing Merino ewes were treated with metyrapone (cortisol inhibitor) or betamethasone (cortisol analogue). Lambs exposed to metyrapone in utero were born with hairier birthcoats than the control or betamethasone treatment groups (P < 0.05), displayed a 10% increase in staple length and a reduction in crimp frequency for the first three shearings (P < 0.05). Co-expression network analysis of microarray data revealed up-regulation of members of the transforming growth factor-β and chemokine receptor superfamilies, gene families known to influence hair and skin development. These experiments demonstrate that presumptive transient manipulation of maternal cortisol status coinciding with the initiation of fetal wool follicle development results in long-term alteration in fleece characteristics, namely fibre length and fibre crimp frequency. These results indicate it is possible to alter the lifetime wool production of Merino sheep with therapeutics targeted to gene expression during key windows of development in utero. Lifetime characteristics of wool, such as fibre diameter, are determined during distinct periods in utero. The aim of this study was to determine if transient manipulation of maternal cortisol status could alter the fleece characteristics of Merino sheep. We demonstrated that treatment with an inhibitor of cortisol biosynthesis, metyrapone, during the first wave of fetal wool follicle development significantly increased the hairiness of lambs and the fibre lengths of adult sheep, hence indicating that improvements in fleece characteristics can occur by alteration of the maternal environment. [ABSTRACT FROM AUTHOR]

Clostridial infection of the intestine can result in necrotic enteritis (NE), compromising production and health of poultry. Mucins play a major role in protecting the intestinal epithelium from infection. The relative roles of different mucins in gut pathology following bacterial challenge are unclear. This study was designed to quantify the expression of mucin and mucin-related genes, using intestinal samples from an NE challenge trial where birds were fed diets with or without in-feed antimicrobials. A method for quantifying mucin gene expression was established using a suite of reference genes to normalize expression data. This method was then used to quantify the expression of 11 candidate genes involved in mucin, inflammatory cytokine, or growth factor biosynthesis (IL-18, KCF, TLR4, TFF2, TNF-α, MUC2, MUC4, MUC5ac, MUC5b, MUC13, and MUC16). The only genes that were differentially expressed in the intestine among treatment groups were MUC2, MUdS, and MUC5ac. Expression of MUC2 and MUC13 was depressed by co-challenge with Eimeria spp. and Clostridium perfringens. Antimicrobial treatment prevented an NEinduced decrease in MUC2 expression but did not affect MUdS. The expression of MUC5ac was elevated in birds challenged with Eimeria spp./C. perfringens compared with unchallenged controls and antimicrobial treatment. Changes to MUG gene expression in challenged birds is most likely a consequence of severe necrosis of the jejunal mucosa. [ABSTRACT FROM AUTHOR]

Gene expression profiles of LM from beef cattle that underwent significant postweaning undernutrition were studied using complementary DNA (cDNA) microarrays. After 114 d of undernutrition, the RNA from LM showed 2- to 6-fold less expression of many genes from the classes of muscle structural proteins, muscle metabolic enzymes, and extracellular matrix compared with animals on a rapid growth diet. The expression levels of these genes had mostly returned to pretreatment levels after 84 d of realimentation. The gene expression changes associated with undernutrition and BW loss showed an emphasis on downregulation of gene expression specific to fast-twitch fibers, typical of starving mammals, with a preferential atrophy of glycolytic fast-twitch fibers. We also identified a small group of genes that showed 2- to 5-fold elevated expression in LM after 114 d of undernutrition. Putative roles for these genes in atrophying skeletal muscle are regulation of myogenic differentiation (CSRP3), maintenance of mesenchymal stem cells (CYR61), modulation of membrane function (TM4SF2), prevention of oxidative damage (SESN1), and regulation of muscle protein degradation (SQSTM1). A significant increase in stearoyl-CoA desaturase (SCD) gene expression was observed in atrophying muscle, suggesting either that increased fatty acid synthesis is part of the tissue response to caloric restriction, or that SCD plays another role in energy metabolism in the mixed cellular environment of bovine skeletal muscle. [ABSTRACT FROM AUTHOR]

Changing dietary protein and amino acids may impact intestinal barrier function. Experiments were conducted in broiler chickens to evaluate supplementation of L-glutamine, glycine, and L-arginine in a reduced protein (RP) diet. Experiment 1 examined the growth performance of broilers fed 5 dietary treatments: 1) a standard diet; 2) an RP diet (193.9 g/kg CP in grower and 176.9 g/kg CP in finisher); 3) RP diet supplemented with 10 g/kg L-Gln; 4) RP diet supplemented with 10 g/kg Gly; 5) RP diet supplemented with 5 g/kg L-Arg. Each experimental diet was replicated 6 times with 10 birds per replicate. In a subset of 96 birds, experiment 2 tested the 4 RP diets with and without dexamethasone (DEX) to induce leaky gut. Each diet was replicated 24 times. Fluorescein isothiocyanate dextran (FITC-d) was used to test intestinal permeability (IP). Gene expression of selected tight junction proteins in ileal and jejunal tissues was assayed by quantitative PCR. From day 7 to 35, the RP diet increased feed intake (FI) (P < 0.05) and body weight gain (BWG) compared with the standard diet while Gln reduced FI and BWG (P < 0.05) compared with RP. Gly had no effect on BWG or FCR. Supplementation of Arg improved FCR from day 21 to 35 and day 7 to 35. In experiment 2, Arg tended to lower FITC-d (P = 0.086). DEX increased passage of FITC-d into the serum (P < 0.001). The villi surface area was increased in birds fed higher Arg (P < 0.05). DEX and diet interacted (P < 0.01) for jejunal claudin-3 mRNA level where DEX upregulated claudin-3 for all diets except the Arg diet. In summary, with a moderate reduction of protein, satisfactory performance can be obtained. Although Gln and Gly had no demonstrable positive effect on IP and performance of broilers, increasing the dietary Arg by approximately 140% improved FCR and showed indications of improved intestinal barrier function of birds fed an RP diet under a stress model. [ABSTRACT FROM AUTHOR]

Maternal feed allowance during pregnancy can affect the development of the ovine placenta and fetus. The impact of variations in feed allowance prior to as well as throughout pregnancy has received less attention. Ewes were offered 0.6 (R), 1.2 (C) or 1.8 (AL) maintenance requirements from 89 days before conception until day 133 of pregnancy. Ewes were euthanised on days 50, 92 and 133 of pregnancy. Ewe live weight and body condition score, maternal and fetal metabolic and hormonal profiles, fetal body dimensions and organ weights, and the number, weight and morphology of placentomes were measured. Maternal live weight and condition score were lower in R compared to AL ewes at all stages of pregnancy (P<0.05). Plasma glucose and albumin concentrations of R ewes were significantly reduced (P<0.05) at mid and late gestation, respectively. Placental components were generally unresponsive to long term variations in maternal feed allowance. However, placental weight was significantly (P<0.05) correlated with fetal weight at days 50 (r=0.59) and 133 (r=0.69) of gestation. By late gestation growth-retarded singleton fetuses from R ewes were 19% lighter (P<0.05), with reduced abdominal (9%) and thoracic (10%) girths (P<0.05) but of similar crown-rump length compared with fetuses from AL ewes. These differences were associated with significantly reduced IGF-I concentrations in fetal plasma (P<0.05). In conclusion, maternal, placental and fetal adaptations to long established planes of variable maternal feed allowance were able to maintain fetal growth during early and mid-pregnancy while fetal growth restriction, associated with reduced fetal IGF-I levels, became apparent in late pregnancy.

The effect of varying short-term maternal feed intake during the peri-conception period on the development of ovine fetal muscle at mid-gestation was investigated. Superovulated donor Merino ewes (n = 24) were fed a roughage/grain pelleted diet (10.1 MJME/kg dry matter) at either 1.5x maintenance (H; high) or 0.5x maintenance (L; low) from 18 days before until 6 days after ovulation. Embryos were transferred to recipient ewes (n = 60) on day 6. Singleton fetuses were collected on day 75 of gestation and placental weights, fetal body dimensions and fetal organ and muscle weights recorded. The number, type and size of muscle fibres and the dry matter, RNA, DNA and protein content in the semitendinosus muscle were determined. Maternal feed intake did not influence body dimensions, organ development or muscle weights in the fetus. However, L feed intake decreased total muscle fibre number in the fetus by approximately 20% (P = 0.06) compared to H feed intake. This resulted from a reduced secondary to primary fibre ratio (P < 0.05) and indicated that secondary fibre formation occurred at a reduced rate in L fetuses. In addition, protein:DNA ratio tended to be lower in muscles of L fetuses (P < 0.1). It is concluded that restricting feed intake over the peri-conception period reduces or delays myogenesis in fetal sheep. The potential mechanisms by which nutritional availability during this period may influence subsequent myogenic development are discussed.