Effects of limited and excess protein intakes of pregnant gilts on carcass quality and cellular properties of skeletal muscle and subcutaneous adipose tissue in fattening pigs

The aim of this study was to investigate whether dietary protein intake of gilts during gestation below (50%) or above (250%) recommendations affects body composition, carcass and meat quality, and properties of skeletal muscle and subcutaneous adipose tissue (SCAT) in offspring at d 83 and 188 of age. German Landrace gilts were fed isoenergetic gestation diets (~13.7 MJ of ME/kg) containing a low (LP, 6.5%; n = 18), an adequate (AP, 12.1%; n = 20), or a high (HP, 30%; n = 16) protein content from mating until farrowing. Within 48 h of birth, offspring were cross-fostered to sows fed a standard diet. On d 83 of age, no effects of the LP diet on BW and body composition were detected, whereas HP pigs showed a slight growth delay (P = 0.06) associated with increased relative weights of small intestine (P < 0.01) and brain (P = 0.08), and reduced relative thymus weight (P < 0.01). On d 188 of age, BW was not different among the dietary groups. However, the carcass of LP pigs contained less (P = 0.01) lean and more (P = 0.07) fat compared with AP and HP pigs, which was only pronounced in pigs originating from large litters (P < 0.05). Like skeletal muscles (P = 0.06), the heart muscle weighed less (P = 0.02) in LP than AP pigs. Compared with AP pigs, LP pigs exhibited a fewer (P = 0.09) total number of myofibers in semitendinosus muscle plus LM both at d 83 and 188 of age, whereas total muscular DNA was less (P = 0.02) at d 188 only. The mRNA abundance of IGF2 measured on d 188 was reduced in SCAT (P = 0.03) and LM (P = 0.07) of LP compared with AP pigs. No changes in muscular fiber type frequency, capillary density, or creatine kinase activity, as well as SCAT adipocyte size and number, were observed at either stages of age. Meat quality characteristics remained unchanged at d 83, whereas Warner-Bratzler shear force value in LM was decreased (P = 0.03) in LP compared with AP pigs on d 188 of age. The results suggest that the maternal LP diet impairs prenatal myofiber formation, reduces the potential of postnatal lean growth related to reduced IGF2 mRNA expression and myonuclear accumulation, and consequently changes carcass quality toward reduced lean proportion and improved tenderness at market weight. In contrast, except for a slight transient growth delay, excess dietary protein during gestation seems to have little effect on the fetal programming of postnatal muscle and adipose tissue phenotype of the progeny.     

Effects of the myostatin F94L substitution on beef traits

This study investigated the effects of a SNP in the myostatin gene (MSTN or growth differentiation factor 8, GDF8) on birth, growth, carcass, and beef quality traits in Australia (Aust.) and New Zealand (NZ). The SNP is a cytosine to adenine transversion in exon 1, causing an amino acid substitution of leucine for phenylalanine(94) (F94L). The experiment used crosses between the Jersey and Limousin breeds, with the design being a backcross using first-cross bulls of Jersey x Limousin or Limousin x Jersey breeding, mated to Jersey and Limousin cows. Progeny were genotyped for the myostatin SNP and phenotyped in Aust., with finishing on feedlot (366 calves, over 3 birth years) and in NZ with finishing on pasture (416 calves, over 2 birth years). The effect of the F94L allele (A allele) on birth and growth traits was not significant. The F94L allele in Limousin backcross calves was associated with an increase in meat weight (7.3 and 5.9% of the trait mean in Aust. and NZ, respectively, P < 0.001), and a reduction in fat depth (-13.9 and -18.7% of the trait means on live calves (600 d) and carcasses, respectively, Aust. only, P < 0.001), intramuscular fat content (-8.2% of the trait mean in Aust., P < 0.05; -7.1% in NZ, not significant), total carcass fat weight (-16.5 and -8.1% of the trait mean, Aust. and NZ; P < 0.001 and P < 0.05, respectively). Meat tenderness, pH, and cooking loss of the M. longissimus dorsi were not affected by the F94L variant. In the Jersey backcross calves, additive and dominance effects were confounded because the F94L allele was not segregating in the Jersey dams. The combined effects, however, were significant on LM area (4.4% in both Aust., P < 0.05, and NZ, P < 0.01), channel fat (-11.7%, NZ only, P < 0.01), rib fat depth (-11.2%, NZ only, P < 0.05), and carcass fat weight (-7.1%, NZ only, P < 0.05). The results provide strong evidence that this myostatin F94L variant provides an intermediate and more useful phenotype than the more severe double-muscling phenotype caused by knockout mutations in the myostatin gene.     

Evaluation of procedures to predict fat-free lean in swine carcasses

The objectives were to develop equations for predicting fat-free lean in swine carcasses and to estimate the prediction bias that was due to genetic group, sex, and dietary lysine level. Barrows and gilts (n = 1,024) from four projects conducted by the National Pork Board were evaluated by six procedures, and their carcass fat-free lean was determined. Pigs of 16 genetic groups were fed within weight groups one of four dietary regimens that differed by 0.45% in lysine content and slaughtered at weights between 89 and 163 kg. Variables in equations included carcass weight and measures of backfat depth and LM. Fat-free lean was predicted from measures of fat and muscle depth measured with the Fat-O-Meater (FOM), Automated Ultrasonic System (AUS), and Ultrafom (UFOM) instruments, carcass 10th-rib backfat and LM area (C10R), carcass last-rib backfat (CLR), and live animal scan of backfat depth and LM area with an Aloka 500 instrument (SCAN). Equations for C10R (residual standard deviation, RSD = 2.93 kg) and SCAN (RSD = 3.06 kg) were the most precise. The RSD for AUS, FOM, and UFOM equations were 3.46, 3.57, and 3.62 kg, respectively. The least precise equation was CLR, for which the RSD was 4.04 kg. All procedures produced biased predictions for some genetic groups (P < 0.01). Fat-free lean tended to be overestimated in fatter groups and underestimated in leaner ones. The CLR, FOM, and AUS procedures overestimated fat-free lean in barrows and underestimated it in gilts (P < 0.01), but other procedures were not biased by sex. Bias due to dietary lysine level was assessed for the C10R, CLR, FOM, and SCAN procedures, and fat-free lean in pigs fed the lowlysine dietary regimen was overestimated by CLR, FOM, and SCAN (P < 0.05). Positive regressions of residuals (measured fat-free lean minus predicted fat-free lean) on measured fat-free lean were found for each procedure, ranging from 0.204+/-0.013 kg/kg for C10R to 0.605+/-0.049 kg/kg for UFOM, indicating that all procedures overestimated fat-free lean in fat pigs and underestimated it in lean pigs. The pigs evaluated represent the range of variation in pigs delivered to packing plants, and thus the prediction equations should have broad application within the industry. Buying systems that base fat-free lean predictions on measures of carcass fat depth and muscle depth or area will overvalue fat pigs and undervalue lean pigs.     

肌糖原含量与猪生产性能、胴体品质及肉质性状间的关系

试验比较2个不同基因型猪肌糖原含量、生长性能、胴体品质和肉质的差异,并分析肌糖原含量与生长性能、胴体品质及肉质之间的相关关系。将7头纯种汉普夏阉公猪体重为(19.48±1.1)kg和6头长撒公猪体重为(20.5±1.5)kg在相同条件下进行单圈饲养,到体重达100kg左右时屠宰,并测定肌糖原、胴体品质和肉质。结果表明:汉普夏猪比长撒猪有较高的日增重(P>0.05),较高的肌糖原含量(P<0.05);长撒猪有较高的背膘厚(P<0.01),较低的屠宰率(P<0.05)、眼肌面积和瘦肉率(P<0.01);汉普夏猪有较低的pH2(P<0.05)、剪切力(P<0.05)和b值(P<0.01),但滴水损失和失水率(P<0.05)高于长撒猪。相关分析结果表明:肌糖原含量与眼肌面积和瘦肉率呈正相关,与剪切力、滴水损失、平均日增重、b值、pH1和pH2呈负相关,而与平均日增重、屠宰率和胴体长相关性不大。这表明肌糖原含量是影响猪胴体品质和肉质的一个重要因素。     

N-甲基D,L-天冬氨酸对肥育猪生长性能和胴体品质的影响

本试验以杜长大肥育猪为试验对象 ,研究了N 甲基D ,L 天冬氨酸对其生长性能和胴体品质的影响。结果表明 ,在日粮中添加 50mg/kgN 甲基D ,L 天冬氨酸使肥育猪 ( 1 )日增重提高 9.31 % (P <0 .0 1 ) ,饲料转化率提高 7.1 6 % (P <0 .0 2 ) ;( 2 )胴体瘦肉率提高 6 .53% (P <0 .0 1 ) ,脂肪比率降低 1 1 .76 %(P <0 .0 1 ) ,背膘厚降低 1 9.72 % (P <0 .0 1 ) ,眼肌面积提高 2 1 .0 1 % (P <0 .0 4 ) ;( 3)背最长肌、股二头肌和半膜肌重量分别增加 1 1 .3% (P <0 .0 1 )、1 0 .0 9% (P <0 .0 1 )和 1 4 .4 4% (P <0 .0 1 )。     

Growth performance,dry matter and nitrogen digestibilities,serum profile,and carcass and meat quality of pigs with distinct genotypes

We investigated the effect of distinct genotypes on growth performance, DM and N digestibilities, serum metabolite and hormonal profiles, and carcass and meat quality of pigs. Eight control-line and eight select-line pigs with an equal number of gilts and castrated males per genotype were chosen from the group of pigs subjected to selection for lean growth efficiency. Pigs were housed individually and allowed ad libitum access to common grower, finisher 1, and finisher 2 diets when they reached approximately 20, 50, and 80 kg, respectively, and water throughout the study. Although genotype had no effect on growth performance during the finisher 2 phase and overall, select-line pigs grew faster and more efficiently (P < 0.05) during the grower and finisher 1 phases than did control-line pigs. Dry matter and N digestibilities during the grower phase were lower (P < 0.05) in select-line pigs compared with control-line pigs. Select-line pigs had less ultrasound backfat (P < 0.05) at the end of the grower and finisher 2 phases. Serum urea N (P < 0.05) and leptin concentrations were lower in select-line pigs than in control-line pigs, but the effect of genotype on serum glucose, triglyceride, or insulin concentration was rather inconsistent. Select-line pigs had heavier heart (P < 0.05), liver (P = 0.08), and kidneys (P < 0.01), implying a higher metabolic activity. Less 10th-rib carcass backfat (P < 0.01) and a trend for larger carcass longissimus muscle area (P = 0.10) were reflected in the greater (P < 0.01) rate and efficiency of lean accretion in select-line pigs. Select-line pigs had lower subjective meat color (P < 0.01), marbling (P < 0.05), and firmness (P < 0.01) scores. Final serum leptin concentration was correlated positively with carcass backfat thickness (r = 0.73; P < 0.01) and negatively with overall feed intake (r = -0.77; P < 0.01). These results indicate that pigs with distinct genotypes exhibited differences in the growth rate, metabolite and hormonal profiles, and body composition. Further research is necessary to determine whether pigs with distinct genotypes respond differently to dietary manipulations, which would have an effect on developing optimal feeding strategies for efficient and sustainable pig production.     

Growth performance, carcass composition, quality, and enhancement treatment of fresh pork identified through deoxyribonucleic acid marker-assisted selection for the Rendement Napole gene

Progeny (n = 70) from unrelated, DNA tested, Rendement Napole carrier (RN-/rn+) Hampshire sires, and DNA tested, Rendement Napole normal (rn+/rn+) Yorkshire dams were genotyped for the segregating RN- allele via DNA marker-assisted methodology. Six slaughter groups ensued, with littermates all being represented within the same slaughter group. Boneless pork loins were removed from right carcass sides after a 48-h chill at 2 degrees C. The anterior portions of the loins were not enhanced, whereas the posterior sections were enhanced with a solution containing 0.5% sodium chloride and 0.5% sodium tripolyphosphate to 110% of their initial weight. Carcasses of carrier pigs had less (P < 0.05) 10th rib fat depth and a greater (P < 0.01) percentage carcass lean than carcasses of normal pigs. Postmortem LM pH of carrier pigs was lower (P < 0.002) at 3, 6, 12, and 24 h, and tended to be lower (P = 0.062) at 48 h compared with that of normal animals. Samples of LM from carrier pigs had greater (P < 0.01) glycolytic potential values, drip loss percentages, and a* values, and lower pH values at fabrication than LM from normal pigs. No genotype differences (P > 0.05) were found for LM lactate, L*, or b* values. Nonenhanced semimembranosus samples from carrier pigs exhibited greater (P < 0.05) purge loss percentages and L* values, and lower (P < 0.01) pH values than samples from normal pigs. Enhanced LM samples exhibited greater (P < 0.05) drip and purge loss percentages, greater pH, and lower L* values at fabrication, regardless of Napole status. These findings suggest that the Napole gene has a positive influence on carcass leanness but detrimental effects for lean quality, which were often further compounded when meat was subjected to enhancement treatment.     

Synergistic effects of betaine and conjugated linoleic acid on the growth and carcass composition of growing Iberian pigs

An experiment was conducted to determine the efficacy of dietary betaine, CLA, or both as growth promotants and carcass modifiers in growing Iberian pigs. Twenty gilts (20 kg of BW) were individually penned and fed barley- and soybean meal-based diets (12% CP, 0.81% Lys, and 14.8 MJ of ME/kg of DM) containing either no added betaine or CLA (control), 0.5% betaine, 1% CLA, or 0.5% betaine + 1% CLA, at 95% of ad libitum energy intake. An additional group of 5 pigs was slaughtered at the beginning of the experiment to obtain the initial body composition. At 30 kg of BW, a balance experiment was conducted. At 50 kg of BW, pigs were slaughtered and viscera was removed and weighed. Betaine or CLA alone did not affect growth performance. However, betaine + CLA increased ADG (601 vs. 558 g, P = 0.03) and gain relative to ME intake (25.4 vs. 22.2 g/MJ, P = 0.03) compared with control pigs. Digestibility of nutrients and metabolizability of energy did not differ among diets (P = 0.46 to 0.75). Carcass protein, water, and lean deposition (g/d) increased (19.8, 24.2, and 23.4%, respectively, P < 0.01) in pigs fed betaine + CLA compared with control pigs. Similarly, protein deposition relative to ME intake increased by 28% in betaine + CLA-supplemented pigs (P < 0.05). Fat and mineral deposition did not differ among treatments. Carcass protein, water, and lean content (g/kg of carcass) of pigs fed betaine + CLA-supplemented diets tended to increase (P = 0.07 to 0.09) and carcass fat content tended to decrease (P = 0.09). Similarly, estimated composition of carcass gain was affected, such that water and lean content tended to increase (P = 0.06 to 0.08), whereas fat tended to decrease (P = 0.08) in pigs fed betaine + CLA-supplemented diets. Longissimus muscle area was not altered by treatments (P = 0.49). The liver of pigs fed betaine + CLA diets had increased weight (19%, P < 0.05) compared with control pigs. Overall, dietary supplementation of betaine + CLA increased ADG, protein, water, and lean deposition in growing Iberian gilts. There appears to be a synergistic action when betaine and CLA are used together.     

Effects of porcine somatotropin administration on the responses to dietary lysine and a near-ideal blend of amino acids for growing pigs

Two experiments were conducted to assess the effects of porcine ST (pST) on the responses to a near-ideal blend of AA for pigs from 22 to 60 kg BW. Eighty Hampshire × Yorkshire gilts (40 gilts/experiment) were individually penned and assigned to a 4 × 2 factorial arrangement of treatments, consisting of 4 diets with and without pST injection. A fortified corn-soybean meal basal diet was formulated to contain 1.50% total Lys and Thr, Met, and Trp were added to obtain a near-ideal blend of these AA relative to Lys. In 3 additional diets, Lys was reduced to 1.25%, 1.00%, or 0.75% by diluting the basal diet with cornstarch, cellulose, and sand, such that the diets also contained the same ratios of AA. Pigs that received pST were administered a daily intramuscular injection of 2 mg of pST. Data from the 2 experiments were pooled. Administration of pST increased ADG (P < 0.01), G:F (P < 0.01), and LM area (P < 0.01), and decreased ADFI (P < 0.03), last rib backfat (P < 0.01), and 10th rib backfat (P < 0.01). Also, estimated carcass muscle and calculated lean gain increased (P < 0.01) in pST-treated pigs. Administration of pST also increased (P < 0.01) the percentage, total gain and accretion rate of water, protein, and ash in the carcass, and decreased (P < 0.01) the percentage, total gain, and accretion rate of carcass fat. Growth rate, G:F, and carcass traits improved (P < 0.01), percentage of carcass proteinand water increased (P < 0.01), and carcass fat percentage decreased (P < 0.01) with increasing dietary Lys. The percentage, total gain, and accretion rate of carcass protein increased to a greater extent in pST-treated pigs than in untreated pigs, resulting in a pST × Lys interaction (P < 0.05). The results indicated that pST improves performance, leanness, and protein accretion in pigs from 22 to 60 kg BW, and that these responses to dietary Lys and a near-ideal blend of AA is greater in growing pigs treated with pST than untreated pigs.     

Effects of ractopamine on performance and composition of pigs phenotypically sorted into fat and lean groups

Crossbred barrows (n = 144; 80 kg) from four farrowing groups were phenotypically selected into fat (FAT) and lean (LEAN) pens using ultrasound. The difference in 10th-rib fat depth between the LEAN and FAT groups was > or =0.5 cm. Within a farrowing group, pigs were assigned to pens (five pigs per pen and eight pens per phenotype) to equalize pen weight and fat depth. Pigs were fed a corn-soybean meal diet containing 19% CP, 1.0% added animal/vegetable fat, and 1.1% lysine (as-fed basis). Half the pens received 10 ppm (as-fed basis) of ractopamine (RAC) during the 28-d finishing phase. At 7-d intervals, live weight and feed disappearance were recorded to calculate ADG, ADFI, and G:F, and 10th-rib fat depth and LM area were ultrasonically measured to calculate fat-free lean and fat and muscle accretion rates. During the first 7 d on feed, LEAN pigs fed RAC gained less (P < 0.05) than FAT pigs fed RAC or LEAN and FAT pigs fed the control diet (RAC x phenotype; P = 0.02); however, RAC did not (P > 0.25) affect ADG after the second, third, and fourth weeks, or over the entire 28-d feeding period. Although wk-2 and -3 ADG were higher (P < or = 0.03) in LEAN than in FAT pigs, phenotype did not (P = 0.08) affect overall ADG. Dietary RAC decreased (P < or = 0.05) ADFI over the 28-d feeding trial, as well as in wk 2, 3, and 4, but intake was not (P > 0.20) affected by phenotype. Neither RAC nor phenotype affected (P > 0.10) G:F after 7 d on trial; however, RAC improved (P < or = 0.04) wk-3, wk-4, and overall G:F. Lean pigs were more efficient (P < or = 0.05) in wk 2 and 3 and over the duration of the trial than FAT pigs. Ultrasound LM accretion (ULA) was not (P > or = 0.10) affected by RAC; however, LEAN pigs had greater (P < or = 0.02) ULA in wk 2 and 4 than FAT pigs. Although fat depth was lower (P < 0.01) in RAC-fed pigs than pigs fed the control diet, ultrasound fat accretion rate indicated that RAC-pigs deposited less (P = 0.04) fat only during wk 4. In addition, calculated fat-free lean (using ultrasound body fat, ULA, and BW) was increased (P < 0.05) in RAC pigs after 3 and 4 wk of supplementation. In conclusion, RAC enhanced the performance of finishing swine through decreased ADFI and increased G:F, whereas carcass lean was enhanced through decreases in carcass fat and increases in carcass muscling.     

Influence of a conjugated linoleic acid mixture on growth, organ weights, carcass traits and meat quality in growing pigs

Grain soybean meal diets, either with 2% of a conjugated linoleic acid (CLA) preparation or with 2% rapeseed oil (control), were tested in 2 × 40 pigs, Pietrain × (Landrace × Large White), each group with 20 female in the live weight range 23.5–117.0 kg and 20 male-castrated pigs in the live weight range 23.5–110.6 kg. The CLA-content of the preparation amounted to 54.0% cis / trans + trans / cis , 8.7% cis/cis and 32.7% trans / trans isomers. Daily weight gain, feed intake and feed : gain ratio were not influenced by the diets tested. The carcass lean increased significantly from 57.2% of the control group to 58.7% in the CLA group (p   < 0.05). The male-castrated showed a stronger CLA effect than the female pigs – not only was the carcass lean significantly increased by 2%, but backfat thickness was significantly decreased by 2.8 mm, i.e. minus 11% (as compared with barrows of the control). The meat of CLA-fed pigs had a higher conductivity. A CLA effect on further meat quality characteristics (pH 45 min post-mortem, impedance, colour criteria, intramuscular fat, drip loss, frying loss, shear force, sensory attributes) could not be detected. There were some significant correlations between the meat quality attributes.     

松辽黑猪IGF-Ⅰ基因外显子4多态性及与部分生产性能的关系

以IGF-Ⅰ基因作为松辽黑猪生长和胴体性状的候选基因，采用PCR-SSCP方法检测30头松辽黑猪IGF-Ⅰ基因外显子4(179 bp)的多态性，对该基因的不同基因型与生长和胴体性状的关系进行分析。结果表明，IGF-Ⅰ基因的2个等位基因和3种基因型在松辽黑猪中均有不同频率的分布，遗传多态性较高; IGF-Ⅰ不同基因型对断奶后日增重有显著影响，AA型显著高于AB型和BB型(P<0.01)。AA型猪的瘦肉率显著低于AB型和BB型(P<0.01)，而AA型猪的平均背膘厚显著高于AB型和BB型(P<0.01)，对其它性状的影响差异不显著。因此，IGF-Ⅰ基因的遗传分析结果说明该基因对松辽黑猪的平均日增重、瘦肉率和平均背膘厚等3个性状有显著的遗传影响，可以初步推断IGF-Ⅰ基因可能是影响猪生长和胴体性状的一个主效基因或是一个与影响猪生长和胴体性状的QTL连锁的基因。     

甜菜碱对生长猪的生长性能和胴体组成的影响

选用 96头杜长大生长猪 ,随机分成 4组 ,以研究日粮中添加不同水平甜菜碱 (10 0 0、15 0 0、2 0 0 0 mg/kg)对猪生长性能、胴体组成及肉质的作用效果。试验结果表明 ,与对照组相比 ,日粮中添加 10 0 0 mg/kg和 15 0 0 mg/kg甜菜碱组猪日增重分别提高 13.2 0 % (P<0 .0 1)、9.2 8% (P<0 .0 5 ) ,日均采食量分别增加 7.30 % (P<0 .0 5 )、7.33% (P<0 .0 1) ,料重比分别下降 7.93% (P<0 .0 1)、6 .5 5 % (P<0 .0 5 )。此外 ,10 0 0 mg/kg甜菜碱组猪的胴体瘦肉率和眼肌面积比对照组分别提高 7.15 % (P<0 .0 5 )、19.12 % (P<0 .0 5 ) ,胴体脂肪率与背膘厚分别减少 2 7.2 1% (P<0 .0 5 )、14 .86 % (P<0 .0 5 ) ;背最长肌中的肌红蛋白和肌内脂肪分别提高 34.2 1% (P<0 .0 1)、2 9.5 6 % (P<0 .0 1)     

Myostatin allelic status interacts with level of nutrition to affect growth, composition, and myofiber characteristics of lambs

The objective of this experiment was to determine if growth, carcass composition, and myofiber characteristics of lambs were affected by heterozygosity for a myostatin mutation (g+6723G>A) when offered differing allowances of feed administered with or without ractopamine. Heterozygote [MSTN A/G (n = 40)] and homozygote wildtype [MSTN G/G (n = 39)] castrate male lambs were individually fed ad libitum (HI; 1.8 × estimated ME(m)) or a restricted allowance (LO; 1.1 × estimated ME(m)) of a diet (191 g of CP/kg of DM and 12 MJ of ME/kg of DM), supplemented with (0.4 mg/kg of BW) or without the β-adrenergic agonist ractopamine (RAC or NO RAC) for 47 d. The lambs were scanned by computed tomography at the beginning and completion of the feeding experiment to calculate composition of lean, fat, and bone in the carcass component of the body. The MSTN A/G HI intake lambs had significantly greater total daily carcass growth (P = 0.045) and loin eye depth (P = 0.022) and tended to have a greater daily growth of lean (P = 0.09) in the carcass, compared with MSTN G/G HI intake lambs. Conversely, MSTN A/G LO intake lambs tended to have less daily lean deposition (P = 0.09), significantly less total daily carcass growth (P = 0.045), and had a greater percentage of type IIX myofibers (P < 0.01) and total myofiber area (relative area) of type IIX myofibers (P = 0.013). The inclusion of RAC increased final BW (P = 0.03) and ADG (P = 0.02), percentage of type IIC (P < 0.001) and IIA (P = 0.012) myofibers, cross-sectional area of types I (P = 0.04) and IIAX (P = 0.04) fibers, and the relative area of type IIC (P = 0.003) and IIA (P = 0.01) myofibers in the LM. The experiment demonstrated that including RAC in the diet of lambs increased final BW and ADG, but not HCW, and increased proportion of type IIC and IIA myofibers and cross-sectional area of type I and IIAX myofibers. Our data suggest that RAC and the heterozygous myostatin mutation act together to increase growth of muscle on a high plane of nutrition. The experiment also demonstrated that poor nutritional background of lambs heterozygous for the myostatin mutation may negatively influence their growth rates and myofiber characteristics.     

对氨基苯胂酸对肥育猪生长性能和肉质的影响及其机理研究

1 2 0头“长嘉 (兴 )”肥育猪按体重、性别和遗传基础分成对照组和试验组 (每组三个重复 ,每个重复2 0头 ) ,分别饲喂含对氨基苯胂酸 (PAPAA)为 0和 70mg/kg的饲粮 ,进行 80天饲养试验 ,随后屠宰测定。结果表明 ,添加PAPAA使日增重提高 8.7% (P <0 .0 5) ,饲料转化率提高 1 1 .5% (P <0 .0 1 ) ,胴体瘦肉率提高 6.7% (P <0 .0 5) ,脂肪率降低 3.5% (P <0 .0 5) ,并发现眼肌面积提高 9.3% (P <0 .0 5)、大理石纹评分提高 5.0 % (P <0 .0 5)。残留测定显示 ;停药 4天后肌肉中砷含量达到国家卫生标准。组织分析发现 :饲粮中添加PAPAA使猪血清生长激素 (GH)浓度升高 4 4.0 % (P <0 .0 5)、胰岛素降低 2 3.4 % (P <0 .0 5) ;背最长肌、肾上腺和腺垂体cAMP含量分别提高 4 8.6%、30 .3%和 57.5% (P <0 .0 3)。上述结果揭示PA PAA似通过影响猪的内分泌系统机能而发挥其促进生长和改善胴体组成的效果     

Changes in hormones, growth factor and lipid metabolism in finishing pigs fed betaine

An experiment was conducted to investigate the effect of dietary betaine supplementation on carcass characteristics, hormones, growth factor and lipid metabolism in finishing pigs. Forty-eight crossbred barrows and gilts (Seghers × Seghers × Duroc) weighing about 55 kg were divided into two groups, each with three replicates of eight pigs (four barrows and four gilts) per replicate, and fed corn–soybean meal basal diets supplemented with 0 and 0.125% betaine for 42 days. At trial termination, two pigs (one barrow and one gilt) weighing about 90 kg were selected from each replicate and slaughtered for analyses. The results showed that betaine increased carcass lean percentage and longissimus muscle area by 5.19% (P < 0.01) and 17.85% (P < 0.01), respectively, and decreased carcass fat percentage and average backfat thickness by 13.07% (P < 0.01) and 10.30% (P < 0.05), respectively. Serum growth hormone, insulin-like growth factor I, free triiodothyronine, free thyroxine and insulin levels in pigs fed betaine were elevated by 45.61% (P < 0.01), 55.50% (P < 0.01), 57.95% (P < 0.01), 51.80% (P < 0.01) and 42.34% (P < 0.05), respectively. Fatty acid synthase activity in the 10th rib subcutaneous adipose tissue was decreased by 24.35% (P < 0.05) with betaine supplementation, whereas hormone-sensitive lipase activity was significantly increased (P < 0.05). Meanwhile, serum free fatty acids concentration in betaine-fed pigs was 25.75% higher compared to controls (P < 0.01). The study suggested that betaine could induce changes in hormones and growth factor in finishing pigs, and therefore could inhibit fat synthesis through reducing lipogenic enzymes activities and promote fat degradation by increasing hormone-sensitive lipase activity, with a resultant decrease in adipose tissue mass and improvement in carcass characteristics.     

绵羊Myostatin基因shRNA慢病毒载体的构建与鉴定

针对绵羊Myostatin基因特异性序列,设计4对shRNA,并合成高表达载体。将干扰质粒和高表达载体瞬时共转染HEK293细胞,应用Real-time PCR鉴定干扰效率,将筛选到最有效的shRNA表达载体和pDONR221载体进行BP重组反应,以获得含干扰序列的入门载体。然后将含干扰序列的入门载体和慢病毒表达的目的载体pLenti6/BLOCK-iT-DEST进行LR重组反应,以获得含干扰序列的慢病毒表达载体。qPCR检测病毒物理滴度。结果本试验成功构建绵羊Myostatin基因RNAi慢病毒载体,病毒的滴度为：9.3×109 TU/mL。为研究Myostatin基因对肌肉生长的影响提供了稳定感染细胞载体。     

Interactive effect of ractopamine and dietary fat source on pork quality characteristics of fresh pork chops during simulated retail display

Crossbred pigs (n = 216) were used to test the interactive effect, if any, of ractopamine (RAC) and dietary fat source on the performance of finishing pigs, pork carcass characteristics, and quality of LM chops during 5 d of simulated retail display (2.6 degrees C and 1,600 lx warm-white fluorescent lighting). Pigs were blocked by BW and allotted randomly to pens (6 pigs/pen), and, after receiving a common diet devoid of RAC for 2 wk, pens within blocks were assigned randomly to 1 of 4 diets in a 2 x 2 factorial arrangement, with 5% fat [beef tallow (BT) vs. soybean oil (SBO)] and RAC (0 vs. 10 mg/kg). Diets were formulated to contain 3.1 g of lysine/Mcal of ME and 3.48 Mcal/kg of ME. Across the entire 35-d trial, pigs fed RAC had greater (P < 0.01) ADG and G:F, but RAC did not affect (P = 0.09) ADFI; however, performance was not affected (P >or= 0.07) by dietary fat source. Carcass weight, LM depth, and lean muscle yield were increased (P < 0.01), whereas fat depth was decreased (P = 0.01), in carcasses from RAC-fed pigs; however, carcass composition measures were similar (P >or= 0.27) between fat sources. Feeding 10 mg/kg of RAC reduced (P 相似文献