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 3mo(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.     

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.     

Effects of low and high levels of maternal nutrition consumed for the entirety of gestation on the development of muscle,adipose tissue,bone, and the organs of Wagyu cattle fetuses

This study aimed to investigate the effects of high and low levels of energy intake during the entire gestation period on the skeletal muscle development, organ development, and adipose tissue accumulation in fetuses of Wagyu (Japanese Black) cows, a breed with highly marbled beef. Cows were allocated to a high-nutrition (n = 6) group (fed 120% of the nutritional requirement) or low-nutrition (n = 6) group (fed 60% of the nutritional requirement). The cows were artificially inseminated with semen from the same sire, and the fetuses were removed by cesarean section at 260 ± 8.3 days of fetal age and slaughtered. The whole-body, total muscle, adipose, and bone masses of the fetal half-carcasses were significantly higher in the high-nutrition group than the low-nutrition group (p = 0.0018, 0.009, 0.0004, and 0.0362, respectively). Fifteen of 20 individual muscles, five of six fat depots, nine of 17 organs, and seven of 12 bones that were investigated had significantly higher masses in the high-nutrition group than the low-nutrition group. The crude components and amino acid composition of the longissimus muscle significantly differed between the low- and high-nutrition groups. These data indicate that maternal nutrition during gestation has a marked effect on the muscle, bone, and adipose tissue development of Wagyu cattle fetuses.     

Vitamin A regulates intramuscular adipose tissue and muscle development:promoting high-quality beef production

During growth in cattle, the development of intramuscular adipose tissue and muscle is dependent upon cell hyperplasia (increased number of adipocytes) and hype...     

Intercellular signaling between adipose tissue and muscle tissue

Adipose and muscle tissues undergo regulated growth and differentiation processes that are modulated by a wide range of factors. The interactions between myogenic cells and adipocytes play a significant role in growth and development, including the rate and extent of myogenesis, muscle growth, adipogenesis, lipogenesis/lipolysis, and in the utilization of energy substrates. Important hormones and growth factors involved in the regulation of these processes include glucocorticoids, insulin-like growth factors, various cytokines, insulin, and leptin. Interactions among these axes have important implications in their influence on relative fat and lean deposition and the efficiency of energy utilization in growth and development. As research progresses to better clarify the interactions among adipose tissue depots and muscle of different fiber types, pathways will become better understood, ultimately leading to the optimized management of fat and lean growth in domestic livestock species. This review will focus on elements of intercellular signaling, using data from cell culture studies to illustrate specific examples of signaling pathways between cells.     

肌肉生长抑制素调控肌肉和脂肪组织代谢的研究进展

肌肉生长抑制素(myostatin,MSTN),又名生长分化因子-8(growth differentiation factor 8,GDF-8),是一种主要由骨骼肌分泌的蛋白质,在肌肉生长发育过程中起负调控作用。若MSTN基因编码区碱基突变或缺失,可以导致肌肉异常肥大,出现典型的"双肌"性状。近年来研究还发现,MSTN在脂肪组织中也表达,并在脂肪沉积的过程中发挥重要调控作用。因此,本文将从MSTN的基因结构、组织分布、作用机制以及功能等几个方面的相关研究进展进行综述,重点阐述其在肌肉和脂肪组织中的调控作用及机制,以期更深入了解MSTN,为畜牧业新品种的改良和肉质性状的改善奠定理论基础。     

Postnatal development of glucose transporter proteins in bovine skeletal muscle and adipose tissue.

Facilitated diffusion of glucose across the plasma membrane is mediated by a family of glucose transporter (GLUT). GLUT1 is ubiquitously present in all tissues and involved in cellular glucose uptake, while GLUT4 plays a key role in cellular glucose uptake stimulated by insulin in skeletal muscles and adipose tissue. To examine the postnatal change in the GLUTs of ruminants, the protein levels of GLUT1 and GLUT4 were measured by Western blot analysis of skeletal muscles, adipose tissue and brain of Holstein male calves aged from 0 to 12 months. Analysis of rumen short chain volatile fatty acids revealed that rumen fermentation increased around 2-3 months old. The GLUT1 level did not change in all tissues examined during the postnatal period, while the GLUT4 levels in skeletal muscle and subcutaneous adipose tissue decreased gradually, and at 12 month old, it was about 40% of those seen at 0 month old. These results are contrast to those in non-ruminant species, in which GLUT4 increases during postnatal development, and may be related to the insulin-resistance seen in adult ruminants.     

Foetal development of skeletal muscle in bovines as a function of maternal nutrition,foetal sex and gestational age

To determine the effects of maternal nutrition on modifications of foetal development of the skeletal muscle and possible increase in the potential of skeletal muscle growth in cattle, gestating cows were either fed 190% NRC recommendations (overnourished; ON) or 100% NRC recommendation (control; CO). Interaction between maternal nutrition (MN) and the foetal sex (FS) was also investigated. Foetuses were necropsied at four different time points throughout gestation (139, 199, 241 and 268 days of gestation) to assess the mRNA expression of myogenic, adipogenic and fibrogenic markers in skeletal muscle. Phenotypic indicators of the development of skeletal muscle fibres, intramuscular lipogenesis and collagen development were also evaluated. Modifications in mRNA expression of skeletal muscle of foetuses were observed in function of MN and FS despite the lack of effect of MN and FS on foetal weight at necropsy. Maternal ON increased the mRNA expression of the myogenic marker Cadherin‐associated protein, beta 1 (CTNNB1) and adipogenic markers Peroxissome proliferator‐activated receptor gamma (PPARG) and Zinc finger protein 423 (ZNF423) at midgestation. However, no differences on foetal skeletal muscle development were observed between treatments at late gestation indicating that a compensatory development may have occurred on CO foetuses making the effect of MN on skeletal muscle development not significant at late gestation. Moreover, our data have shown an evidence of sexual dimorphism during foetal stage with a greater skeletal muscle development in male than in female foetuses. In conclusion, providing a higher nutritional level to pregnant cows changes the trajectory of the development of skeletal muscle during midgestation, but apparently does not change the potential of post‐natal growth of muscle mass of the offspring, as no differences in skeletal muscle development were observed in late gestation.     

Brown adipose tissue development and metabolism in ruminants

We conducted several experiments to better understand the relationship between brown adipose tissue (BAT) metabolism and thermogenesis. In Exp. 1, we examined perirenal (brown) and sternum s.c. adipose tissue in 14 Wagyu x Angus neonates infused with norepinephrine (NE). Perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum s.c. adipocytes contained a few, small mitochondria, with poorly developed cristae. Lipogenesis from acetate was high in BAT but barely detectable in sternum s.c. adipose tissue. In Exp. 2, we compared perirenal and tailhead adipose tissues between NE-infused Angus (n = 6) and Brahman (n = 7) newborn calves. Brahman BAT contained two-to-three times as many total beta-receptors as Angus BAT. The mitochondrial UCP1:28S rRNA ratio was greater in Brahman BAT than in BAT from Angus calves. Lipogenesis from acetate and glucose again was high, but lipogenesis from palmitate was barely detectable. Tail-head s.c. adipose tissue from both breed types contained adipocytes with distinct brown adipocyte morphology. In Exp. 3, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types, whereas the UCP1 gene expression tripled during gestation in both breed types. At birth, palmitate esterification was twice as high in Angus than in Brahman BAT and was at least 100-fold higher than in BAT from NE-infused calves from Exp. 2. Uncoupling protein-1 mRNA was readily detectable in tailhead s.c. adipose tissue in all fetal samples. In Exp. 4, male Brahman and Angus calves (n = 5 to 7 per group) were assigned to 1) newborn treatment (15 h of age), 2) 48 h of warm exposure (22 degrees C) starting at 15 h of age, or 3) 48 h of cold exposure (4 degrees C) starting at 15 h of age. Brahman BAT adipocytes shrank with cold exposure, whereas Angus BAT adipocytes did not. Similarly, BAT from neonatal lambs (Exp. 5; n = 6 per group) was depleted of lipid in response to cold exposure, although UCP1 gene expression persisted. In Exp. 4, NE stimulated lipogenesis from palmitate in BAT incubated in vitro. Lipogenesis from palmitate was higher in Angus than in Brahman BAT, and increased with both warm and cold exposure. These studies suggest that BAT from Brahman calves may be exhausted of lipid shortly after birth during times of cold exposure.     

Differentiation of adipose tissue and muscle in hypophysectomized pig fetuses

In the present study, fetuses were hypophysectomized (hypox) in utero on d 72 to 74 of gestation with an electrical cauterizing needle. One to six successfully hypox fetuses were removed on d 110 of gestation from each of five gilts. Subcutaneous adipose tissue samples and semitendinosus muscles were obtained from the hypox fetuses and an equal number of control fetuses. Body weights of control fetuses (n = 15; mean +/- SE, 1,195 +/- 33 g) were similar to weights of hypox fetuses (n = 15; 1,179 +/- 67 g). Fat cell size in the middle subcutaneous layer of adipose tissue was increased in hypox fetuses (P less than .01) compared with control fetuses. The number of obvious fat cell clusters (outer layer) in lipid stained sections was reduced (P less than .01) by 50% in hypox fetuses. Histochemical reactions for glucose-6-phosphate dehydrogenase, esterase and lipoprotein lipase (LPL) activities in middle layer cell clusters were considerably enhanced in sections from hypox fetuses compared with sections from controls. Quantitative analysis of percent light transmittance (Zeiss photometer) through LPL-stained cell clusters indicated an increase (P less than .001) in LPL staining in sections from hypox fetuses when compared with sections from control fetuses. Transverse muscle sections (cryostat) from hypox fetuses failed to show normal patterns (as seen in control muscles) of reactions for acid ATPase, malate dehydrogenase (NAD-dependent), NADH-TR and alpha-glycerol phosphate dehydrogenase (without NAD). The number of muscle fibers that were stained for these enzymes was greatly reduced in hypox fetuses compared with control fetuses. The number of lipid positive fibers was also reduced in hypox fetuses compared with control fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)     

The fatty acid composition of muscle fat and subcutaneous adipose tissue of pasture-fed beef heifers: influence of the duration of grazing

Our objective was to determine the effect of the duration of grazing before slaughter on the fatty acid composition of muscle fat and s.c. adipose tissue (SAT) of beef heifers. Sixty crossbred Charolais heifers (n = 15 per treatment) were assigned randomly to one of four dietary treatments: 45 animals (Treatments 1, 2, and 3, respectively) were housed at the beginning of the experiment, and 15 (Treatment 4) were fed at pasture. Two groups of 15 heifers were moved to pasture 40 d (Treatment 2) and 99 d (Treatment 3) before slaughter, respectively, resulting in preslaughter grazing periods of 0, 40, 99, or 158 d for Treatments 1, 2, 3, and 4, respectively. Before grazing the predominantly perennial ryegrass pasture, animals were housed and offered grass silage ad libitum and 3 kg of concentrate diet (650 g of grass silage/kg of total DMI). After slaughter, the fatty acid profile of the neutral (NL) and polar lipid (PL) fractions of muscle fat from the LM and the total lipids from SAT were analyzed by gas chromatography. Duration of grazing showed a quadratic tendency on mean carcass weight (P = 0.08), but did not affect growth (P = 0.27) or the lipid content (P = 0.13) of the LM. Increasing the duration of grazing led to a linear increase (P < 0.001) in the concentration (on fresh-tissue basis) of CLA in muscle fat (from 11.80 to 17.75 mg/100 g of muscle in NL, and from 0.52 to 0.82 mg/100 of g muscle in PL) and in SAT (from 3.98 to 10.23 mg/g of SAT; P < 0.001), and increased the concentration of C18:1trans-11 in both muscle fat fractions (P < 0.001) and in SAT (P < 0.001). In the total muscle lipids, the polyunsaturated to saturated fatty acid ratio (P:S) increased from 0.12 to 0.15 with increased duration of grazing following a linear (P < 0.05) and cubic pattern (P < 0.05). Increasing the duration of grazing led to a linear decrease in the n-6:n-3 ratio of muscle fat from 2.00 to 1.32 (P < 0.001), and from 2.64 to 1.65 in the SAT lipids (P < 0.001), mainly as a consequence of the increased concentration of C18:3n-3. It is concluded that muscle fat and SAT fatty acid profile was improved from a human health perspective by pasture feeding, and that this improvement depended on the duration of grazing.     

Lipid composition of muscle and adipose tissue from crossbred ram, wether and cryptorchid lambs

Lambs from rams (R), cryptorchids (C) and wethers (W) were examined to compare with the dietary guidelines for humans on fat and cholesterol intake. Twenty-four lambs were assigned to treatments as R, C or W at weaning (60 d). Each lamb had ad libitum access to a 77:23% forage:concentrate diet containing 11.7% crude protein and 1.84 Mcal ME/kg. The experiment was terminated when the lambs reached 50 kg body weight. Lipid composition of the longissimus muscle (LM) and s.c. adipose tissue was determined by gas-liquid chromatography. Rams has less (P less than .01) s.c. fat (cm) and i.m. lipid (%) (.26 cm; 3.*%) than W (.56 cm; 4.9%). Total polyunsaturated fatty acids were greater (P less than .01) in the LM of R (7.06%) than in LM of W (5.21%). Rams had higher percentages of C18:2, C18:3, C20:4 and C18:1 in their LM than W did. On the basis of a 100-g serving of LM, R had 1.73, C had 2.15 and W had 2.21 g saturated fatty acids. There were no (P less than .01) differences among sex types for cholesterol content of LM, which averaged 66.6 mg/100 g wet tissue. The only major difference of the s.c. fat lipid composition was in saturated fatty acids. Wethers had higher (P less than .01) saturated fatty acids (51.4%) than C 46.8%) and R (43.3%). Based on the lipid composition of these three types of lambs, the LM muscle from young R lambs approached dietary fat guidelines for humans more closely than did that from castrates.     

Bovine sirtuins: initial characterization and expression of sirtuins 1 and 3 in liver, muscle, and adipose tissue

Sirtuins, the mammalian homologs of the silent information regulator 2 gene of Saccharomyces cerevisiae, are members of the NAD(+)-dependent family of histone deacetylases. In vertebrates, 7 sirtuins have been described, with different cellular localizations and target proteins. Glucose and lipid metabolism are among the processes regulated by these enzymes. In ruminants, gluconeogenesis is the main biochemical pathway by which glucose is obtained. Because sirtuins in bovines have not been studied, the aim of this work was to obtain sequences coding for the 7 sirtuins and determine the expression patterns of sirtuin1 (Sirt1) and sirtuin3 (Sirt3) in the liver, muscle, and adipose tissue of calves and bulls. Using PCR amplification, we obtained sirtuin gene sequences and reported them to the National Center for Biotechnology Information GenBank. Characteristic sequence motifs corresponding to the sirtuin catalytic core domain were found, including the active and zinc-binding sites. Relative expression patterns of Sirt1 and Sirt3 in liver, muscle, and adipose tissue were quantified by real-time PCR, normalizing to the geometric mean of the housekeeping genes cyclophilin A and β-actin. Expression of Sirt1 was less in liver and muscle, whereas it was greater in adipose tissue of adult animals, with statistical differences (P=0.0071) only in the latter. In the case of Sirt3, expression was greater in all 3 adult tissues, but statistical differences were found only in liver (P=0.0141) and muscle (P=0.0017). The greatest expression was observed in liver for Sirt1 and in muscle for Sirt3, whereas the least expression was in muscle for Sirt1 and in adipose tissue for Sirt3. In other species, sirtuin expression (both Sirt1 and Sirt3) in liver is reported to be the greatest among these 3 tissues, a pattern different from what we measured. These differences in expression can be associated with metabolic differences between nonruminant and ruminant species. However, further research on the relationship between bovine sirtuins and ruminant metabolism is required for a better understanding of these fields.     

Growth, carcass characteristics, and lipid composition of adipose tissue and muscle of pigs fed canola

Sixty-one finishing pigs (53.4 kg) were fed a control diet (containing soybean meal) or diets containing 20% intact canola (IC) or 20% ground canola (GC) for 8 wk. Diets were not isocaloric. Daily gain and feed efficiency were not affected by dietary treatment, but pigs fed GC ate less than pigs fed either IC or the control diet. Carcass measurements, obtained on 43 of the pigs, were not affected by diet. For 27 pigs, fatty acid composition of perirenal adipose tissue (PRF), subcutaneous adipose tissue (SCF), and longissimus muscle (LDM) was analyzed. Nine pigs (three per treatment) were randomly selected for fatty acid composition analysis of intramuscular adipose tissue (IMF) and for cholesterol analysis of several tissues. Pigs fed canola had greater (P less than .05) proportions of mono- and polyunsaturated fatty acids and less (P less than .05) saturated fatty acids in PRF and SCF. The differences were more pronounced for PRF than for SCF. In the LDM, pigs fed canola tended to have elevated levels of unsaturated fatty acids at the expense of the saturated fatty acids, but this effect was significant for linolenic acid only. The fatty acid composition of IMF was not affected by diet (P greater than .05). Diet did not alter the cholesterol content of the tissues, but cholesterol in IMF was higher (P less than .05) than in PRF, SCF, and LDM. In conclusion, 20% IC or GC did not alter growth performance or carcass characteristics of pigs. Feeding of canola increased the degree of unsaturation of PRF and SCF, but it had less effect on IMF and LDM.     

Dietary protein-induced changes in porcine muscle respiration, protein synthesis and adipose tissue metabolism

Growth rate, physically separable tissues of the ham and loin, heat production, skeletal muscle respiration and protein synthesis, and lipogenesis and lipolysis in s.c. adipose tissue were measured in a single experiment in which pigs were offered a 13 (n = 8), or 21% (n = 6) protein diet from 20 to 100 kg live weight. Pigs that were fed the 13% protein diet gained body weight slower, ate less, converted feed less efficiently and took 31 d longer to reach 100 kg live weight. Fat depth (cm) was greater (P less than .05) and loin eye area (cm2) was less (P less than .01) in pigs fed the 13% protein diet (2.6 vs 2.3 and 29.8 vs 35.3). Pigs that were fed the 13% protein diet had lower (P less than .05) ham and loin separable muscle and greater (P less than .05) ham and loin separable fat. The mean heat production was less (P less than .05) in pigs offered the 13% (22.49) vs 21% (24.63 MJ/d) protein diets. In the intercostal muscle preparation, total and Na+,K+-ATPase-dependent respiration (microliter O2.mg-1.h-1) were lower (P less than .05) in pigs offered the 13% (2.39 and .41) vs the 21% (3.89 and .68) protein diets. The energy used for the support of Na+ transport across membrane accounted for approximately 17% of muscle respiration. Absolute rates of protein synthesis in the muscle preparations were lower (P less than .01) at 13 than at 21% dietary protein. Lipogenesis in s.c. adipose tissue was not affected by dietary protein level. There was no difference in basal and norepinephrine-stimulated lipolysis between the two dietary protein levels.     

Coordinate regulation of ovine adipose tissue gene expression by propionate

The current study examined the acute effects of intravenous propionate infusion on plasma hormones and metabolites and the expression of adipose tissue lipogenic genes. Four yearling rams were assigned to one oftwo groups (saline or propionate infusion) in a crossover design. All sheep were cannulated in both jugular veins and infused with 1.2 M propionate at a rate of 64 micromol x mix(-1) x kg BW(-1) for 30 min. Blood samples were collected at -10, 0, 5, 10, 20, 30, 60, and 120 min after initiation of infusion. Subcutaneous adipose tissue biopsies were obtained from the tailhead at 0 and 2 h after propionate infusion and analyzed for gene expressions of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, leptin, and uncoupling protein-2 using a nonisotopic ribonuclease protection assay. The partial cDNA of the enoyl reductase region of ovine fatty acid synthase was cloned and sequenced from s.c. adipose tissue of sheep. The deduced amino acid sequence (210 amino acids) was 86% identical to human, 88% identical to rat, 88% identical to mouse, and 72% identical to chicken. Plasma glucose and insulin concentrations abruptly increased 5 min after beginning propionate infusion and further increased up until 30 min but were unaffected in saline-infused sheep (P < 0.05). Plasma concentration of NEFA decreased (P < 0.05) during propionate infusion, whereas IGF-I levels were unaltered. The amounts of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, and leptin mRNA increased (P < 0.05) in s.c. adipose tissue of propionate-infused sheep compared with those of saline-infused sheep. However, uncoupling protein-2 mRNA decreased (P < 0.05) in propionate-infused sheep. This study demonstrates that an acute nutrient challenge, in the form of i.v. propionate, can stimulate or inhibit the expression of various adipose tissue genes involved with lipogenesis and adipose tissue metabolism.     

母体营养对后代肌肉生长发育的影响

骨骼肌占机体干重的50%以上,是机体的重要组成部分。肌肉的发育受很多因素的调控,而在关键窗口期,母体营养对其影响是至关重要的。母体营养状况可以改变后代肌纤维的数目、密度、肌肉的代谢、胰岛素敏感性和肌内脂肪的沉积。本文就母体营养对后代肌肉发育的影响作一简要概述。     

Fatty acid composition of muscle and adipose tissue from crossbred bulls and steers

Fatty acid composition of total lipid extracts of muscle and adipose samples from crossbred bulls (N = 34) and steers (N = 35) was determined by gas-liquid chromatography. Samples of semitendinosus, triceps brachii and longissimus muscle and of subcutaneous and perinephric adipose tissue were excised from the right side of each carcass. In addition, thin-layer chromatography was utilized to obtain phospholipid and triacylglycerol fractions from total lipid extracts of semitendinosus and longissimus muscle and subcutaneous adipose tissue from 10 bull and steer cohorts (N = 20). The most prominent sex condition effect was in percentage of total poly-unsaturated fatty acids (PUFA). Bull tissues contained higher (P less than .01) percentages of PUFA than those of steers at all sampling sites. This reflected higher percentages of linoleate (C18:2), linolenate (C18:3) and arachidonate (C20:4) in bull tissues. Most of the PUFA were present as phospholipids in muscle samples. The fatty acid composition of muscle phospholipids was similar regardless of sex condition or muscle sampled. Total lipid extracts of semitendinosus and triceps brachii muscles of both bulls and steers contained from 6 to 10% more unsaturated fatty acids (UFA) compared with M. longissimus. Muscle triacylglycerols contained relatively high percentages of saturated fatty acids (SFA). Semitendinosus and longissimus samples from steers contained higher (P less than .05 and P less than .01, respectively) percentages of total SFA than those from bulls. Steer samples contained slightly higher percentages of palmitic acid (C16:0) compared with bulls at all sampling sites, and this difference was significant for M. longissimus. The fat:lean ratio of muscle tissue is the major factor that determines fatty acid composition.     

Influence of environmental temperature on growth, muscle and adipose tissue metabolism, and meat quality in swine.

An experiment involving 32 individually housed, castrated male pigs was conducted to determine the effects of environmental temperature (12 degrees C = T12 or 28 degrees C = T28) on the performance, carcass characteristics, muscle and adipose tissue metabolism, and meat quality of pigs fed to achieve equal rates of weight gain between 8 and 92 kg live weight. The T12 pigs had less muscle (P less than .01) and more subcutaneous fat (P less than .01) in the ham than did T28 animals. Thyroids and adrenals were heavier (P less than .01) in T12 than in T28 pigs. Percentage of type I muscle fibers was higher (P less than .01) and fiber cross-sectional areas smaller (P less than .01) in semispinalis muscle (SS) of T12 pigs, whereas no effect of temperature was noticed in longissimus muscle (LD). Cold exposure induced a larger increase in oxidative metabolism in SS (+30 to 32%, P less than .001) than in LD (+14 to 17%, P less than .10) and an enhanced glycolytic metabolism in LD (P less than .05). Lipid concentration was higher in SS of T12 than in that of T28 pigs. Lipogenic enzyme activities and unsaturation of backfat were higher in T12 than in T28 pigs, whereas no effect of temperature was noticed in leaf fat. Cold treatment resulted in a faster postmortem pH decline (P less than .01), higher glycolytic potential (P less than .01), and lower ultimate pH (P less than .01) in LD. The results indicate that 12 degrees C vs 28 degrees C induced detrimental effects on growth, ham composition, and muscle and adipose tissue quality.