影响藏猪与大约克夏猪肌肉品质的lncRNA的筛选及功能分析

旨在分析藏猪和大约克夏猪(180日龄)背最长肌组织中与猪肉质性状相关的长链非编码RNA (lncRNAs)和基因,探讨lncRNAs在猪肉品质中的分子调控作用,为猪肉质性状的改良提供理论依据.本研究根据先前公布的数据,以饲养在相同条件下的180日龄健康藏公猪(n-3)和大约克夏公猪(n-3)为研究对象,收集背最长肌肉品...     

Feeding intensity and dietary protein level affect adipocyte cellularity and lipogenic capacity of muscle homogenates in growing pigs,without modification of the expression of sterol regulatory element binding protein

Muscle fat stores at slaughter partly determine the dietetic and sensory quality traits of pork meat. Nutritional strategies during the growing-finishing period are able to modify intramuscular fat content; however, the underlying mechanisms remain largely unknown. The objective of this study was to determine some of the cellular, biochemical, and molecular bases of muscle fat content variation in response to feeding regimen in pigs. Crossbred pigs of 30 kg BW were allocated to three feeding groups: free access ([C], n = 10) to a standard diet (3.25 kcal of DE/kg, 9.5 g of lysine/kg), standard diet at 75% of the spontaneous voluntary intake ([FR], n = 10), or both low protein and energy intakes ([PR], n = 10) in order to get the same growth rate as the FR pigs and the same body composition as the C pigs. At slaughter (110 kg BW), FR and PR pigs were 30 d older than C pigs (P < 0.001). In agreement with the protocol, carcass adiposity was similar in PR and reduced (P < 0.01) in FR pigs compared with C animals. Lipid content in longissimus lumborum muscle was reduced by 25% in FR pigs and increased by 40% in PR pigs compared to C pigs (P < 0.001). Commensurate variations in the diameter of muscle adipocytes were observed between the three feeding groups (P < 0.001). The muscle activities of malic enzyme and glucose-6-phosphate dehydrogenase, generating reduced nicotinamide adenine dinucleotide phosphate for fatty acid synthesis, were depressed (P < 0.05) in both FR and PR groups, compared to the C group. The expression level of the sterol regulatory element binding protein that was chosen as the putative candidate at the molecular level was not modified by the feeding regimen. No variations in the oxidative enzyme markers were denoted, whereas lactate dehydrogenase activity was reduced by 13% (P < 0.05) in PR group compared to other groups. In conclusion, moderate long-term feed restriction results in decreased lipogenic capacity of muscle adipocytes and intramuscular fat content. In contrast, the reduction of both protein and energy intakes more likely results in an imbalance between multiple aspects of muscle energy metabolism, in favor of intramuscular fat accretion.     

Impact of vitamin and mineral supplement withdrawal and wheat middling inclusion on finishing pig growth performance,fecal mineral concentration,carcass characteristics,and the nutrient content and oxidative stability of pork

A study was conducted to determine if supplement withdrawal (omission of dietary vitamin and trace mineral premixes and a two-thirds reduction in dietary inorganic phosphorus) for 28 d preslaughter and the feeding of wheat middlings (dietary concentrations of 5, 15, and 30% from weaning to 16, 16 to 28, and 28 kg to slaughter, respectively) affect growth performance, carcass characteristics, and fecal mineral concentrations ofthe pig, as well as the nutrient content and oxidative stability of the longissimus dorsi muscle. Crossbred pigs (n = 64) were blocked by weight and assigned to one of four dietary treatments in a 2 x 2 factorial design (with or without supplement withdrawal, and with or without wheat middlings). Supplement withdrawal and wheat middling inclusion did not influence average daily gain (ADG), average daily feed intake, gain/feed, or carcass traits, except for a decrease (P < 0.01) in the ADG of pigs from 28 to 65 kg when fed wheat middlings. Supplement withdrawal decreased (P < 0.01) fecal Ca, P, Cu, Fe, Mn, and Zn concentrations. In diets containing full vitamin and mineral supplementation, wheat middling inclusion decreased (P < 0.01) fecal Ca, Cu, Fe, and Zn concentrations and increased (P < 0.01) fecal Mn. Supplement withdrawal decreased (P < 0.05) concentrations of riboflavin, niacin, and P in the longissimus dorsi muscle, but did not affect longissimus dorsi thiamin, vitamin E, Fe, Cu, Zn, and Ca concentrations. Inclusion of wheat middlings increased (P < 0.04) longissimus dorsi thiamin, niacin, riboflavin, and vitamin E concentrations and decreased (P < 0.04) Cu concentrations. However, wheat middling inclusion did not affect (P > 0.05) longissimus dorsi Ca, P, Fe, and Zn concentrations. Dietary treatment did not affect either Cu/Zn superoxide dismutase or glutathione peroxidase activity in the longissimus dorsi. The results from this study indicate that supplement withdrawal and dietary wheat middling inclusion alter pork nutrient content and fecal mineral concentration, but not the oxidative stability of pork.     

Muscle fibre traits as additional selection criteria for muscle growth and meat quality in pigs – results of a simulated selection

To estimate the direct and correlated responses in meatiness and meat quality, simulated selection was applied using one‐trait selection and index selection including muscle fibre traits. In a total of 2024 pigs of German Landrace, Large White, Leicoma, and Schwerfurter breeds, carcass composition, meat quality, and fibre characteristics of the M. longissimus lumborum were analysed and genetic parameters were calculated by using REML variance component estimation. Coefficients of heritability ranged from low to moderate (growth traits: h² = 0.22–0.32; meat quality traits: h² = 0.17–0.27; muscle fibre traits: h² = 0.12–0.20). The total fibre number and the frequency of white fibres correlated positively with live weight (r_g = 0.44 and 0.44, respectively) and with loin muscle area (r_g = 0.38 and 0.19, respectively) while the relationships to pH value and drip loss were not as close (r_g = ?0.29–0.19). Selection indices were constructed from live weight and muscle area, from pH value and drip loss, and from muscle structure traits. As expected, simulated selection for live weight or loin muscle area lead to direct positive effects but these were associated with negative effects on meat quality traits (selection intensities: SI = 0.1; 0.5). Using selection for an index from loin area and muscle structure (loin muscle area + total fibre number – frequency of white fibres – frequency of giant fibres) the adverse effect on meat quality was minimized (responses in pH value: ?0.05; ?0.01) or was changed towards desired direction (responses in drip loss: ?0.65%; ?0.26%). The results show that fibre characteristics of pig muscle can be used as selection criteria for simultaneous improvement of carcass composition and meat quality in pigs by including indices developed from performance and fibre traits.     

The influence of the PRKAG3 mutation on glycogen,enzyme activities and fibre types in different skeletal muscles of exercise trained pigs

Background

AMP-activated protein kinase (AMPK) plays an important role in the regulation of glucose and lipid metabolism in skeletal muscle. Many pigs of Hampshire origin have a naturally occurring dominant mutation in the AMPK γ3 subunit. Pigs carrying this PRKAG3 (R225Q) mutation have, compared to non-carriers, higher muscle glycogen levels and increased oxidative capacity in m. longissimus dorsi, containing mainly type II glycolytic fibres. These metabolic changes resemble those seen when muscles adapt to an increased physical activity level. The aim was to stimulate AMPK by exercise training and study the influence of the PRKAG3 mutation on metabolic and fibre characteristics not only in m. longissimus dorsi, but also in other muscles with different functions.

Methods

Eight pigs, with the PRKAG3 mutation, and eight pigs without the mutation were exercise trained on a treadmill. One week after the training period muscle samples were obtained after euthanisation from m. biceps femoris, m. longissimus dorsi, m. masseter and m. semitendinosus. Glycogen content was analysed in all these muscles. Enzyme activities were analysed on m. biceps femoris, m. longissimus dorsi, and m. semitendinosus to evaluate the capacity for phosphorylation of glucose and the oxidative and glycolytic capacity. Fibre types were identified with the myosin ATPase method and in m. biceps femoris and m. longissimus dorsi, immunohistochemical methods were also used.

Results

The carriers of the PRKAG3 mutation had compared to the non-carriers higher muscle glycogen content, increased capacity for phosphorylation of glucose, increased oxidative and decreased glycolytic capacity in m. longissimus dorsi and increased phosphorylase activity in m. biceps femoris and m. longissimus dorsi. No differences between genotypes were seen when fibre type composition was evaluated with the myosin ATPase method. Immunohistochemical methods showed that the carriers compared to the non-carriers had a higher percentage of type II fibres stained with the antibody identifying type IIA and IIX fibres in m. longissimus dorsi and a lower percentage of type IIB fibres in both m. biceps femoris and m. longissimus dorsi. In these muscles the relative area of type IIB fibres was lower in carriers than in non-carriers.

Conclusions

In exercise-trained pigs, the PRKAG3 mutation influences muscle characteristics and promotes an oxidative phenotype to a varying degree among muscles with different functions.     

Effects of long‐term microalgae supplementation on muscle microstructure,meat quality and fatty acid composition in growing pigs

We investigated the effects of long‐term microalgae supplementation (7% in a piglet diet and 5% in a fattening diet) on muscle microstructure and meat quality, including fatty acid composition in female Landrace pigs (n = 31). The major effects were muscle‐specific increases in n‐3 and n‐6 polyunsaturated fatty acids (PUFA) concentrations, resulting in increased accumulation of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Carcass traits and meat quality of longissimus thoracis muscle were not affected by the microalgae diet with the exception of reduced drip loss (p = 0.01) and increased protein proportion (p = 0.04). In addition, the microalgae diet resulted in a shift to a more oxidative myofibre type composition in semitendinosus but not longissimus thoracis muscle. In conclusion, microalgae supplementation offers a unique opportunity to enhance essential n‐3 PUFA contents in pig meat. The results support small but coordinated changes in skeletal muscle phenotypic appearance and functionality.     

Influence of the three RN genotypes on chemical composition, enzyme activities, and myofiber characteristics of porcine skeletal muscle.

An experiment was conducted to evaluate the effects of the RN genotype on skeletal muscle characteristics in pigs sharing otherwise the same polygenic background. Animals were genotyped for RN on the basis of RTN (Rendement Technologique Napole) records using segregation analysis methods. Samples of longissimus (L) and semispinalis capitis (S) muscles were taken from 39 rn+/rn+, 38 RN-/rn+ and 37 RN-/RN- pigs slaughtered at 108 +/- 8.6 kg live weight. Activities of lactate dehydrogenase (LDH), citrate synthase (CS), and beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) were measured on both muscles to assess glycolytic, oxidative, and lipid beta-oxidation capacities, respectively. Histological examinations and chemical analyses were performed on L muscle. The energetic metabolism of the white L muscle was more oxidative in RN-/RN- than in rn+/rn+ pigs, as shown by increased CS and HAD activities (P < .001), decreased LDH activity (P < .001), larger cross-sectional area of IIA (P < .05) and IIB-red (P < .05) fibers, higher relative area of IIA fibers ( P < .05), and lower relative area of IIB-white fibers (P < .001). No significant difference was found between heterozygous and homozygous carriers of the RN- allele, except for CS activity, which was lower in RN-/rn+ than in RN-/RN- pigs. In L muscle, the RN- allele led to a large increase in glycolytic potential (+3.5 phenotypic SD between homozygotes) and lightness (+.7 SD), and a decrease in ultimate pH, dry matter, and protein contents (-1.7 to -2 phenotypic SD for these three traits), with an almost completely dominant effect. No differences were found between genotypes for intramuscular fat and hydroxyproline contents. In the red S muscle, the presence of RN- had no influence on enzyme activities. These results indicate that the RN genotype greatly influences compositional and histochemical traits and metabolic enzyme activities in a muscle type-dependent manner, with a completely or incompletely dominant effect of the RN- allele.     

Reduced dietary lysine enhances proportion of oxidative fibers in porcine skeletal muscle

The present study was conducted to elucidate the effects of dietary lysine levels on the proportion of oxidative muscle fibers in porcine muscle. Two 6-week-old barrows from each of five litters were used. Each littermate was assigned to one of two diets, control (lysine content: 1.16%) or low lysine (LL) diet (lysine content: 0.73%). The diets were iso-energetic and iso-protein, and contained all essential amino acids (apart from lysine) in the recommended amounts. The pigs were fed these diets for 3 weeks. Citrate synthase (EC 4.1.3.4) activity in longissimus dorsi and rhomboideus muscles was higher in the LL group ( P  < 0.05). In both muscles, pigs fed the LL diet had a higher proportion of muscle fiber with activities of reduced nicotinic amide adenine dinucleotide dehydrogenase (EC 1.6.5.3, P  < 0.01). The abundance of mRNA of peroxisome proliferator-activated receptor γ coactivator 1α in rhomboideus muscle was higher in the LL group ( P  < 0.05), and those of peroxisome proliferator-activated receptor γ2 were higher in both longissimus dorsi and rhomboideus muscles in the LL group ( P  < 0.05). We conclude that reduced intake of dietary lysine enhances proportion of oxidative muscle fiber, and hence oxidative capacity of porcine muscle.     

Giant muscle fibres in pigs with different Ryr1 genotype

This study examined the frequency, morphological and immunohistochemical characteristics of the giant fibres in the longissimus muscle of local Krsko polje pigs with different Ryr1 genotypes. Giant fibres were round-shaped and had significantly increased cross-sectional area compared with normal muscle fibres. Only fast-twitch glycolytic fibres were affected, usually showing enhanced succinate dehydrogenase activity. On the ultrastructural level, the dilation of the sarcoplasmic reticulum, swelling of mitochondria and destruction of myofilaments was observed. The incidence of giant fibres was the highest in Ryr1 dimutant pigs (Ryr1 nn), which also exhibited lower muscle pH1 than heterozygous (Ryr1 Nn) or pigs with the wild Ryr1 gene (Ryr1 NN). However, the giant fibres were also present in pigs free of Ryr1 gene mutation. Our results suggest that the giant fibre syndrome depends mostly upon the rate and intensity of early post-mortem glycolysis, which results in acidity of muscle tissue. We suppose that the giant fibre formation is a result of excessive intracellular lactate accumulation in some fast-twitch glycolytic fibres. This process could also explain the ultrastructural alterations and the consequent changes in the oxidative enzymes and myofibrillar ATPase staining pattern observed in our and some previous studies.     

Effect of conjugated linoleic acid on meat quality,lipid metabolism,and sensory characteristics of dry-cured hams from heavy pigs

We investigated conjugated linoleic acid (CLA) supplementation administered to heavy pigs, assessing carcass characteristics, meat quality, and sensory characteristics of dry-cured (Parma) ham. Thirty-six pigs, averaging 97 kg BW, were assigned randomly to three feeding groups in which diets were supplemented with either 0, 0.25, or 0.5% (as-fed basis) of a CLA preparation containing 65% CLA isomers. All pigs were slaughtered at 172 kg BW. No (P > 0.05) differences were observed in dressing percentage, loin and ham weight, or pH and color of longissimus and semimembranosus muscle. Tenth-rib backfat thickness tended to be lower (P < 0.10) in carcasses from CLA-fed pigs. The oxidative stability of longissimus muscle was greater (P < 0.05) in pigs fed CLA than control, but only at the longer (300 min) oxidation time. Acetyl-CoA carboxylase activity in adipose tissue of CLA-fed pigs was less (P < 0.05) than that of pigs fed diets devoid of supplemental CLA. Composition of ham fat was markedly affected (P < 0.01) by dietary CLA, with higher saturated fatty acids, lower monounsaturated fatty acids, and higher CLA in the fat of CLA-fed pigs regardless of supplementation level. Although melting quality was improved (P < 0.05), most sensory characteristics and the chemical composition of dry-cured hams were not (P > 0.05) affected by incorporation of CLA. Results indicated that dietary CLA alters lipid metabolism, producing lower concentrations of monounsaturated fatty acids and increased concentrations of CLA isomers in the fat of heavy pigs. Moreover, supplementing diets with CLA produced only minimal improvements in Parma ham sensory traits and had no appreciable effects on fresh pork quality.     

Carcass, muscle and meat characteristics of lean and obese pigs

Six pigs obtained from a lean selected strain and six pigs obtained from an obese selected strain were slaughtered at about 110 kg live-animal weight. Carcasses were evaluated; hams were dissected into bone, skin, fat and lean, and loin samples were obtained for fiber type characteristics, percentage of fat and moisture, collagen analysis, sensory characteristics, textural properties and objective color analysis. Carcasses from lean pigs were longer, had less backfat and larger longissimus muscle cross-sectional areas than carcasses obtained from obese pigs. Hams from lean pigs had less fat, more bone and more lean than hams from carcasses of obese pigs. The percentages and cross-sectional areas of red and white muscle fibers of the longissimus muscle from lean and obese pigs were not different. However, lean pigs had intermediate fibers that were only 79% as large (P less than .10) as intermediate muscle fibers from obese pigs. Intermediate fibers represented only 7 and 10% of total fiber area, whereas white fibers represented 84 and 79% of total fiber area in longissimus muscle of lean and obese pigs, respectively. Overall, lean pigs tended to possess fewer fibers (-16%) per unit of area than obese pigs, indicating that total muscle fiber hypertrophy was partially responsible for the increased longissimus muscle area of the lean strain. Sensory properties of longissimus meat samples from lean and obese strains were not different. However, the shear force requirement of the longissimus samples from the lean strain were slightly, but significantly (P less than .10), higher than those from the obese strain. No differences were observed in meat color.     

Acute immobilization stress in prone position in susceptible Pietrain and resistant Duroc pigs. I: comparison of protein degradation in Duroc and Pietrain pigs' skeletal muscle and liver

The experiment was conducted to determine the relationship between lysosomal proteinase activities in skeletal muscle and liver of stressed pigs. Six‐month‐old Duroc (D) and Pietrain (P) pigs were randomly assigned to either control (group I) or stressed groups (5 min of stress, group II; 15 min of stress, group III; 30 min of stress, group IV; 60 min of stress, group V). At slaughter, the longissimus dorsi muscle and the liver were taken. The tissues were analysed for cathepsin D, acid autolytic activities without and with pepstatin (inhibitor of cathepsin D) and leupeptin (inhibitor of cysteine proteinases). Both tissues were also analysed for RNA, DNA and protein content. The acute immobilization stress in the prone position caused changes in longissimus dorsi muscle in DNA (26% decrease in D and 35% increase in P pigs), functional cell size, protein/10³DNA (FCS) (34% increase in D and 25% decrease in P pigs), increase in acid autolytic activity (AAA) (by 48.3%), pepstatin insensitive acid autolytic activity (PIA) (by 111.8%), leupeptin insensitive acid autolytic activity (LIA) (by 35.8%) in D, but in P pigs by 13.5%, 16.6% and 54%, respectively. The interaction between strain of pigs and stress was also observed, mostly in DNA and AAA's. In the liver, RNA was decreased by 10% in D and by 12.3% in P pigs, DNA by 13% and 24% in D and P pigs, FCS was increased by 13.2% in D and by 22.7% in P pigs; the activity of cathepsin D (CatD) and pepstatin sensitive cathepsin D (PSCatD) increased after 15 min of stress by 9.2% and 9.3% and LIA by 13.7% in D pigs but in P pigs the maximal increase was after 15 min of stress in AAA by 10.3%, in PIA by 13.6% and in LIA by 3.2%. The experiment showed that the proteinase activities in the two different strains of pigs were different. The highest changes were in AAA's in the longissimus dorsi muscle and in CatD and PSCatD in the liver. There was more CatD in the longissimus dorsi muscle and liver of D than P pigs. Although it should be taken with caution, this suggests that other proteinases may be also responsible for the catabolism of proteins.     

不同猪种5-羟色胺受体基因的表达及其与肉质的相关性分析

为研究5-羟色胺（5-HT）受体基因在不同猪种的表达及其与肉质的关系,试验选取淳安花猪与杜长大三元猪各12头,同时饲喂,达上市体重时分别屠宰,测定胴体、肉质性状及肌肉、脂肪中的5-HT受体基因表达量。结果表明：淳安花猪、杜长大三元猪的平均屠宰体重分别为88.1、102.4kg;淳安花猪的板油率、背膘厚、肌内脂肪等指标均显著高于杜长大三元猪（P〈0.05）;屠宰率、眼肌面积杜长大三元猪显著高于淳安花猪（P〈0.05）。5-HT2A、5-HT7受体基因在2个猪种脂肪组织中的表达量均显著高于肌肉组织（P〈0.05）,杜长大三元猪的肌肉中5-HT2A、5-HT7表达量显著低于淳安花猪（P〈0.05）,而脂肪中表达量两猪种间差异不显著。5-HT2A、5-HT7受体基因表达量与屠宰肉质指标之间基本呈负相关,尤其是肌肉中的5-HT2A表达量,呈较强负相关（杜长大三元猪）或显著负相关（淳安花猪）。研究初步认为,5-HT受体基因在中外猪种之间存在表达差异,并与屠宰肉质性状具有相关性。     

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.     

Dietary inclusion of tomato pomace improves meat oxidative stability of young pigs

The aim of this study was to assess the nutritional effect of tomato pomace, in combination with two distinct fat sources (lard or soya bean oil), on longissimus lumborum muscle, subcutaneous fat and liver of young pigs. Forty male pigs of 4 weeks old were randomly assigned to four dietary treatments using two fibre sources (wheat bran or 5.0% tomato pomace) and two fat sources (lard or soya bean oil), in a 2 × 2 factorial design for a 5‐week trial. Tomato pomace did not improve colour, fatty acid profile, cholesterol content or lipid oxidation, nor did it yield detectable levels in lycopene or β‐carotene in the meat (p > 0.05). However, a positive increase in α‐tocopherol content of meat and liver was observed in pigs fed tomato pomace (p < 0.05). Compared with lard, soya bean oil increased MUFA and PUFA proportions and decreased the percentage of SFA (p < 0.05). Our results indicate that 5.0% of tomato pomace increases pork oxidative stability and that 5.0% of soya bean oil, compared with lard, improves its nutritional quality.     

Dietary mulberry leaf powder affects growth performance,carcass traits and meat quality in finishing pigs

This study was conducted to evaluate the effect of mulberry leaves as an alternative source of protein on growth performance, carcass traits and meat quality in finishing pigs. A total of 180 Xiangcun Black pigs were randomly assigned to five treatment groups with six pens of six pigs per pen. The pigs were provided with a basal diet or a diet contained 3%, 6%, 9% or 12% of mulberry leaf powder during a 50‐day experiment period. The results showed that dietary mulberry leaf powder had no negative effect on growth performance in Xiangcun Black pigs, except in the 12% mulberry group, where final body weight and average daily gain decreased (p < .05) and feed to gain ratio of the pigs increased (p < .05). Dietary mulberry inclusion decreased (quadratic, p < .05) the back fat thickness, fibre mean cross‐sectional area (CSA) in the longissimus dorsi (LD) muscle and mRNA expression levels of myosin heavy chain (MyHC) IIb in LD and biceps femoris (BF) muscles, while increased (linear or quadratic, p < .05) the plasma concentration of albumin, levels of crude protein (CP), inosine monophosphate (IMP) and several amino acids in muscle tissues. When compared with the other groups, the 9% mulberry diet increased (p < .05) loin‐eye area and contents of CP and IMP in muscles, while decreased (p < .05) plasma activity of cholinesterase and concentrations of uric acid and urea. The 6% mulberry diet had the lowest fibre mean CSA and shear force and increased total fibre number of the LD muscle, when compared with the other groups. These results suggest that including mulberry in the diet at <12% is an effective feed crop to improve meat quality and the chemical composition of muscle without negatively affecting growth performance.     

基于RNA-seq数据鉴定苏姜猪肉质性状相关基因

试验通过对苏姜猪背最长肌和腿肌进行转录组分析,旨在挖掘影响苏姜猪肌肉肉质性状的候选基因。选取90和180日龄苏姜猪各3头,利用RNA-seq技术对90日龄苏姜猪背最长肌、180日龄苏姜猪背最长肌和腿肌进行测序,对差异表达基因进行GO功能和KEGG Pathway显著性富集分析。结果显示,180日龄苏姜猪背最长肌和90日龄苏姜猪背最长肌中有1 655个基因差异表达,其中474个基因表达上调,1 181个基因表达下调,GO功能和KEGG Pathway显著性富集分析发现,474个表达上调基因主要参与肌肉纤维、转录调节、钙信号通路、MAPK信号通路、胰岛素信号通路、FOXO信号通路等生物学功能,1 181个表达下调基因主要参与免疫、造血、溶酶体、绑定、酶活性等生物学功能;180日龄苏姜猪背最长肌和腿肌中有383个基因差异表达,其中70个基因表达上调,313个基因表达下调,GO功能和KEGG Pathway显著性富集分析发现,70个表达上调基因未能显著富集,313个表达下调基因主要参与细胞分化增殖、肌肉发育、细胞外基质、cGMP-PKG信号通路等生物学功能。本试验获得了苏姜猪背最长肌和腿肌组织的转录组信息,筛选出6个与苏姜猪肉质性状相关的候选基因：FOXO1、FOXO3、FOXO4、MYF6、A-FABP和H-FABP,为深入研究苏姜猪肉质性状的分子机理奠定基础。     

猪骨骼肌纤维类型和能量代谢相关基因的表达特性研究

【目的】研究马身猪、晋汾白猪和杜长大猪骨骼肌肌纤维类型和能量代谢相关基因的表达特性。【方法】选取6月龄马身猪、晋汾白猪和杜长大猪,屠宰后采集背最长肌和趾长伸肌,采用HE染色检测肌纤维的直径、密度和横截面积,通过实时荧光定量PCR分别检测Ⅰ型、Ⅱa型、Ⅱb型和Ⅱx型肌纤维的标记基因(MYH7、MYH2、MYH4和MYH1),线粒体活性相关基因(ATP5A1、PGC1-α和PPARβ),电子传递链活性相关基因(UQCRC2、SDHA、NDUFA9),以及糖酵解活性相关基因(LDHA、LDHB和GK)的表达量。【结果】马身猪背最长肌肌纤维直径和横截面积均显著低于晋汾白猪和杜长大猪,而密度显著高于晋汾白猪和杜长大猪(P<0.05);马身猪和晋汾白猪趾长伸肌肌纤维直径和横截面积均显著低于杜长大猪,而密度显著高于杜长大猪(P<0.05)。马身猪背最长肌MYH7基因的表达量最高,晋汾白猪最低;马身猪和晋汾白猪趾长伸肌MYH7基因的表达量显著高于杜长大猪(P<0.05)。马身猪背最长肌和趾长伸肌MYH2基因的表达量显著高于晋汾白猪和杜长大猪,晋汾白猪趾长伸肌MYH2基因的表达量显著高于杜长大猪(P<0.05)。马身猪背最长肌MYH4基因的表达量显著低于晋汾白猪和杜长大猪,马身猪和晋汾白猪趾长伸肌MYH4基因的表达量显著低于杜长大猪(P<0.05)。马身猪背最长肌中ATP5A1和PGC1-α基因的表达量均显著低于晋汾白猪和杜长大猪,晋汾白猪PGC1-α和PPARβ基因的表达量均显著低于杜长大猪(P<0.05);马身猪和晋汾白猪趾长伸肌中ATP5A1、PGC1-α和PPARβ基因的表达量均显著低于杜长大猪(P<0.05)。晋汾白猪背最长肌中UQCRC2、SDHA和NDUFA9基因的表达量均显著低于杜长大猪和马身猪(P<0.05);晋汾白猪和马身猪趾长伸肌中UQCRC2、SDHA和NDUFA9基因的表达量均显著低于杜长大猪,马身猪UQCRC2和SDHA基因的表达量均显著低于晋汾白猪(P<0.05)。晋汾白猪和马身猪背最长肌和趾长伸肌中LDHA、LDHB和GK基因的表达量均显著低于杜长大猪(P<0.05)。【结论】马身猪骨骼肌肌纤维直径和横截面积都较小,Ⅰ型和Ⅱa型肌纤维标记基因的表达量较高;杜长大猪骨骼肌Ⅱb型肌纤维标记基因的表达量较高,氧化磷酸化和糖酵解相关基因的表达量均较高。     

淮猪及杂交后代肌纤维直径变化及其与肉质关系的研究

对不同品种和杂交组合肥育猪(淮猪、长淮、大长淮)采用单因子试验设计,在相同条件下,研究不同血缘比例对淮猪肌纤维直径的影响。结果表明:淮杂猪的背最长肌和股二头肌肌纤维直径显著高于淮猪(P<0.05)。淮猪的肌纤维直径介于中国地方猪与国外瘦肉型猪之间。肌纤维直径与胴体性状(瘦肉率、眼肌面积、背最长肌全重、背最长肌率、脂肪)呈较强的相关性。淮杂猪肉质理化性状中(肉色评分、大理石纹评分、贮藏损失)3项指标明显变差(P<0.05),但pH值变化不显著。作者认为淮猪杂交后代的肌纤维直径较纯种淮猪粗,淮杂猪肉质也较纯种淮猪差。     

Effect of age at slaughter on carcass traits and meat quality of Italian heavy pigs

Barrows and gilts (n = 128) from four breed crosses were used to investigate the effect of age at slaughter on carcass traits, proteolytic enzyme activity, and meat and fat quality. Pigs were blocked by breed cross into four blocks, and within blocks, one pen (eight barrows and eight gilts) was assigned randomly to be slaughtered at either 8 or 10 mo of age. Pigs were fed a corn-barley-soybean meal finisher diet from 104 +/- 2.5 d of age (37.7 +/- 0.33 kg BW) to the appropriate slaughter age. Carcasses from older (10 mo) pigs had lower (P < 0.01) muscularity indexes and lean cut yields than those of younger (8 mo) pigs, but dressing percentage and longissimus muscle area increased (P < 0.01) with age. Older pigs produced a redder (P < 0.01) and darker (P < 0.05) semimembranosus, with lower (P < 0.01) ultimate pH and cathepsin B and B + L activities, as well as higher (P < 0.01) aminopeptidase hydrolyzing activity than younger pigs. Moreover, the longissimus muscle of pigs slaughtered at 10 mo of age had lower (P < 0.01) drip and cooking loss percentages than that from pigs slaughtered at 8 mo of age. Ham subcutaneous fat from 10-mo-old pigs had greater (P < 0.05) percentages of oleic acid and lower (P < 0.01) proportions of moisture, linoleic, and linolenic acids than subcutaneous fat from pigs slaughtered at 8 mo of age. Results from this study indicate that fresh hams from pigs slaughtered at 10 mo of age would be more suitable for the production of high-quality, Italian, dry-cured hams.