宰前管理对机械化屠宰猪PSE肉的影响

74头商品猪600km-800km运输到达屠场后，被分成饮水组（34）和禁饮组（40），每组再分设宰前休息4、8、12、16和20h组，机械化屠宰后，取背最长肌进行pH、肉色、硬度、系吕力、和水份含量测定，结果饮水组PSE肉平均发生率为17.6%(6/34)，禁饮组为22.5%(9/40）；给水同时间前休息4、8、12、16和20h各组PSE肉发生率分别是16.7%、25.03.3%、22.2%和40.0%，所有试验猪均无DFD肉发生，结果表明：长途运输供机构械化屠宰的猪，在宰前禁饮休息4h和给水休息16h后屠宰可得到较好的肉品质量。     

滩羊与小尾寒羊不同部位羊肉脂肪酸组成的对比分析

为了研究滩羊和小尾寒羊不同部位脂肪酸组成的差异,试验对滩羊和小尾寒羊股二头肌、背最长肌和臂三头肌3个部位31种脂肪酸的停留时间和浓度进行了对比分析。结果表明,31种脂肪酸在滩羊和小尾寒羊不同部位羊肉中的停留时间均为差异不显著(P>0.05),但脂肪酸停留时间随着脂肪酸中碳含量的增加而增加;脂肪酸C16:0、C18:0、C18:2n6c在滩羊和小尾寒羊不同部位羊肉中的浓度均高于其他脂肪酸,脂肪酸C17:0在滩羊和小尾寒羊不同部位羊肉中的浓度呈现极显著差异(P<0.01)。     

12月龄白萨福克与藏羊杂交F_1代羊肌纤维特性研究

试验以12月龄的白-藏羊为研究对象,采用石蜡切片的方法,测定了其背最长肌、臂三头肌和股二头肌的肌纤维直径、肌纤维面积和肌纤维密度。结果表明:白-藏羊公羊的背最长肌、臂三头肌和股二头肌等3个肌肉部位间的肌纤维直径、肌纤维面积和肌纤维密度等差异不显著(P>0.05),母羊的背最长肌、臂三头肌和股二头肌也表现出同样的规律;背最长肌和股二头肌的肌纤维直径、肌纤维面积及肌纤维密度均为公羊高于母羊(P>0.05),臂三头肌的肌纤维面积以母羊略高于公羊,肌纤维直径和肌纤维密度均以公羊高于母羊(P>0.05)。     

猪肉滴水损失不同测定方法的比较以及与猪肉品质和胴体性状的关系

本研究利用三个商业品系776头猪的背最长肌来比较测定滴水损失的两种不同方法，即EZ—滴水损失测定法和袋测定法，并分析滴水损失与猪肉品质和胴体性状之间的关系。袋测定法是将一片重量大约为120g的背最长肌薄片悬挂在密闭的袋内，而EZ—滴水损失测定法是将两个重量大约为10g的样品放在滴水损失容器内。     

不同胴体重对猪轻度PSE肉的理化和感官性状的影响

研究高温环境饲养产生轻度PSE肉与正常肉的猪屠宰性能和肉品质的差异。对体重110～120 kg左右的杜长大三元杂交商品猪屠宰,比较胴体重为80 kg(轻度PSE肉6头,正常肉6头)和85 kg(轻度PSE肉6头,正常肉7头)的屠宰性能、理化与感官特性。结果表明:在胴体重为80～85 kg范围内,随胴体重升高,猪的背膘厚和眼肌面积有所增加(P0.05),正常肉剪切力和弹性随胴体重升高明显上升(P0.05),水分含量显著下降(P0.05)。轻度PSE肉的肌内脂肪随胴体重升高下降显著(P0.05),失水率和剪切力有所升高(P0.05),水分含量随胴体重升高变化不明显(P0.05)。同一胴体重下,轻度PSE肉的猪背膘厚明显比正常猪低(P0.05),眼肌面积无明显差异(P0.05)。轻度PSE肉的失水率、水分和剪切力明显高于正常肉(P0.05),蛋白质含量差异不明显(P0.05)。85 kg胴体重的轻度PSE肉的肌内脂肪和弹性比正常肉低(P0.05)。研究表明:在高温饲养条件下,正常肉的猪背膘厚和肌内脂肪比轻度PSE肉的高,剪切力和失水率比轻度PSE肉的低。在80～85 kg胴体重中,轻度PSE肉随体重的增大肉品质下降,正常肉的肉品质随体重升高变化不明显。     

滇南小耳猪与DLY商品猪背最长肌营养成分比较分析

本试验为比较研究滇南小耳猪与DLY商品猪肉的营养价值,分别检测了53头滇南小耳猪和58头DLY猪背最长肌肉的水分、粗蛋白质、粗脂肪、灰分、氨基酸及脂肪酸等营养成分含量,比较分析其差异性。结果显示,滇南小耳猪背最长肌的水分含量极显著低于DLY商品猪背最长肌（P < 0.01）,粗蛋白质、粗脂肪含量极显著高于DLY商品猪（P < 0.01）,灰分含量差异不显著（P > 0.05）;其中滇南小耳猪背最长肌的7种必需氨基酸（苏氨酸、缬氨酸、蛋氨酸、异亮氨酸、亮氨酸、赖氨酸、苯丙氨酸）、肉豆蔻酸、棕榈酸、油酸、顺式异油酸、11-顺-二十碳烯酸,饱和脂肪酸、单不饱和脂肪酸、总脂肪酸含量均极显著高于DLY商品猪（P < 0.01）。综上所述,滇南小耳猪与DLY猪相比具有更高的营养价值和开发价值。     

杜洛克、大白猪、长白猪纯种后代胴体品质及肌内氨基酸含量的比较

该研究主要对杜洛克、大白猪、长白猪进行屠宰测定和背最长肌氨基酸含量及组成分析。结果表明,杜洛克、大白猪、长白猪的屠宰率分别为76.32%、76.54%、77.27%;眼肌面积分别为43.07 cm~2、53.96 cm2、50.94 cm~2;胴体瘦肉率分别为63.96%、64.84%、66.84%;背最长肌中的氨基酸总量分别为23.33%、23.26%、23.69%;鲜味氨基酸含量分别为17.05%、16.99%、17.34%;必需氨基酸含量分别为8.96%、8.98%、9.14%;3个品种猪的肌肉中均以谷氨酸含量最高,其次为天冬氨酸、赖氨酸、亮氨酸、精氨酸等,而胱氨酸、蛋氨酸含量最低。     

金华猪背最长肌中不同肌球蛋白重链基因表达的发育性变化

为揭示脂肪型金华猪肉质调控相关基因不同生长阶段的表达差异及其与肉质性状的相关性,本研究在评价肉质性状的基础上,采用实时荧光定量PCR方法检测金华猪背最长肌不同肌纤维类型肌球蛋白重链MyHCⅠ、ⅡA、ⅡX和ⅡB基因mRNA表达量在30、90、150 d和180 d间的变化。结果表明:金华猪背最长肌中MyHCⅠ基因mR NA表达量在30 d时最高,随着日龄增加,其表达量极显著降低(P<0.01);与30 d相比,MyHCⅡA、ⅡX、ⅡB在90、150、180 d基因表达水平均显著上升,其中在180 d的表达量达到最高水平(P<0.01)。此外,MyHCⅠmRNA表达量与活体重、眼肌面积、背膘厚、肌内脂肪含量显著负相关(P<0.01),与滴水损失呈显著正相关(P<0.01);而MyHCⅡA、ⅡX、ⅡB基因表达与活体重、眼肌面积、背膘厚、肌内脂肪含量显著正相关(P<0.01),与滴水损失呈显著负相关(P<0.01)。以上结果初步揭示金华猪背最长肌MyHCⅠ、ⅡA、ⅡX、ⅡB基因表达的发育性变化模式,并进一步证明MyHC 4种亚型的mRNA表达量与肉质性状显著相关,为深入研究调控肉质的内在机制提供了基础数据。     

榆林白绒山羊产肉性能及肉品质的研究

<正>榆林市是陕西省畜牧主产区,羊的养殖量居全省之首,2007年羊的存栏量突破500万只,出栏突破300万只,以陕北毛肉兼细毛羊和白绒山羊为主要品种。白绒山羊肉质鲜美、无膻味、适应性强,深受消费者青睐,但作为当地的主要养殖品种,其产肉性能和肉品质却一直没有被系统研究过。因此,研究以当地近年引进的道赛特绵羊为对照,首次对榆林白绒山羊的产肉性能和肉品质进行系统研究,以期为榆林     

民猪和大白猪背最长肌差异表达基因的筛选与注释

为了筛选民猪和大白猪背最长肌中的差异表达基因,本研究采用高通量测序技术,构建了民猪(脂肪型)和大白猪(瘦肉型)背最长肌组织的数字基因表达谱,对差异表达的数字基因进行了筛选与注释,并进行了GO和通路的功能显著性富集分析.结果表明,民猪和大白猪分别获得5 000 000多条可用的标签数据(Clean tag),其中拷贝数大于100的标签所占比例最高,分别为88.62％和84.62％;完全比对到正义链上,且1个标签仅比对到1个基因的分别为2 351 788和2 388 175条.以大白猪为对照组,民猪与之相比,差异倍数在2倍以上的共有1 098个基因,其中44个上调表达,1 054个下调表达,有11个基因只在民猪中表达,256个基因只在大白猪中表达,差异表达基因中包括多个与肌内脂肪含量、脂类代谢、肉色、嫩度和肌肉生长发育相关的基因或转录子.民猪和大白猪分别预测到了23 853个和34 731个定位在猪基因组不同位置的新转录本,其中包含存在1个碱基错配的标签.民猪和大白猪之间的差异基因在细胞所处位置方面显著富集的条目有细胞质、膜旁细胞器、色素粒、水解性液泡、部分细胞内等共计18个;在基因分子功能方面显著富集的条目有蛋白结合和氧化还原酶活性2个;在参与的生物过程方面显著富集的条目有对压力的应答、对活性氧的应答和羧酸代谢过程等14个.显著富集的通路共计11个,按照P值从小到大的顺序,溶酶体、PPAR信号通路和胆汁酸合成通路为差异最显著的3个通路.本研究结果可为今后挖掘新基因和研究影响猪肉品质的遗传因素等提供理论依据.     

Micro-calpain is essential for postmortem proteolysis of muscle proteins

The objective of this investigation was to test the hypothesis that -calpain is largely responsible for postmortem proteolysis of muscle proteins. To accomplish this objective, we compared proteolysis of known muscle proteins in muscles of wild type and micro-calpain knockout mice during postmortem storage. Knockout mice (n = 6) were killed along with control mice (n = 6). Hind limbs were removed and stored at 4 degrees C. Muscles were dissected at 0, 1, and 3d postmortem and subsequently analyzed for degradation of nebulin, dystrophin, metavinculin, vinculin, desmin, and troponin T. In a separate experiment, hind limb muscles from knockout (n = 4) and control mice (n = 4) were analyzed at 0, 1, and 3 d postmortem using casein zymography to confirm that mu-calpain activity was knocked out in muscle and to determine whether or not m-calpain is activated in murine postmortem muscle. Cumulatively, the results of the first experiment indicated that postmortem proteolysis was largely inhibited in micro-calpain knockout mice. The results of the second experiment established the absence of micro-calpain in the muscle tissue of knockout mice and confirmed the results of an earlier study that m-calpain is active in postmortem murine muscle. The results of the current study show that even in a species in which m-calpain is activated to some extent postmortem, micro-calpain is largely responsible for postmortem proteolysis. This observation excludes a major role for any of the other members of the calpain family or any other proteolytic system in postmortem proteolysis of muscle proteins. Therefore, understanding the regulation of micro-calpain in postmortem muscle should be the focus of further research on postmortem proteolysis and tenderization of meat.     

Actions of cathepsins on troponin T during postmortem aging of porcine muscle

In this study, we examined the contribution of the cathepsins (cathepsin D and crude cathepsins containing cathepsins B and L) to troponin T degradation during postmortem aging. The action of cathepsin D on troponin T was examined at various pHs (pH 4.0–6.5). The degradation of intact troponin T was observed at pH 4.0, but not observed at pH 5.5 and 6.5. As a result of the degradation of troponin T, the 30 kDa fragment was not generated in any pH condition. The action of the crude cathepsins on troponin T was also examined at various pHs (pH 4.0–6.5). The intact troponin T was degraded at pH 4.0 and the 30 kDa fragments were observed. These 30 kDa fragments disappeared during further incubation. On the other hand, at pH 5.5 and 6.5, the intact troponin T was degraded and the 30 kDa fragment was accumulated. These results suggested that the cathepsin D scarcely contributed to the degradation of troponin T during postmortem aging, but crude cathepsins containing cathepsins B and L were partially involved in the degradation of troponin T and the generation of 30 kDa fragments.     

Alterations in postmortem degradation of myofibrillar proteins in muscle of lambs fed a beta-adrenergic agonist

Dietary administration of 4 ppm of the beta-agonist L-644,969 (Merck Sharpe and Dohme Research Laboratories) to finishing lambs induced a decrease (10 to 14%, P less than .05) in extractable calpain I activity in the longissimus muscle (LD) at death (d 0). At 4 d postmortem (d 4), extractable calpain I levels in the LD of both control and treated lambs were reduced (P less than .001) from those present at d 0, but the extractable activity in the LD was reduced to a greater extent in control than in treated lambs. Calpain II activity was increased 42% (P less than .005) in LD of treated lambs; however, no significant differences were observed between d 0 and d 4 calpain II activity within treated or control LD samples (P greater than .1). Calpastatin activity was higher in the LD of treated lambs (74% on d 0, P less than .001 and 430% on d 4, P less than .001) than in the LD of control lambs. Measurable cathepsin B activity was decreased (29% on d 0, P less than .05) and measurable cathepsin H activity was increased (10% on d 0, P less than .05 and 10% on d 4, P less than .05) in the LD of treated lambs compared with controls. On d 2, 4 and 6 postmortem, degradation in myofibrils isolated from the LD was lower for treated than for control lambs. Warner-Bratzler shear values for loin chops from treated lambs were higher on both d 3 (111%) and 6 (108%) postmortem than for chops from control lambs (P less than .001). L-644,969-induced decreases in muscle proteolytic capacity may limit postmortem myofibril degradation and contribute to the reduced tenderness observed. This decreased proteolytic capacity may contribute to increased muscularity of L-644,969-treated lambs.     

德州驴不同部位肌肉组织的常规营养成分、氨基酸和矿物质元素含量的比较

试验研究德州驴不同部位肌肉组织中常规营养成分、氨基酸(从)和矿物质元素含量的变化.选取年龄、体重相近的健康德州驴32头采用单因素完全随机试验设计.结果 显示,粗蛋白的含量以臂三头肌最高,臀肌最低.粗脂肪含量呈相反变化规律,臀肌脂肪沉积较好,嫩度更佳.臂三头肌中的多数单--AA以及必需氨基酸(EAA)、非必需氨基酸(NE...     

Rheological characteristics of fresh and frozen PSE, normal and DFD chicken breast meat

1. Textural and rheological differences among broiler breast meat ranging from pale, soft and exudative (PSE) to dark, firm and dry (DFD) in their fresh and frozen (and thawed) forms were investigated. 2. The PSE meat showed significantly higher lightness values and lower pH and water holding capacity values than normal and DFD meats; DFD meat was also significantly different from normal meat. 3. During cooking, PSE meat lost significantly more liquid and produced a softer gel than normal or DFD meats; texture profile analysis parameters were lower for the PSE meat. 4. The storage modulus values (G', rigidity of elastic response of the gelling material) showed that DFD meat produced a more rigid gel during cooking (especially above 54 degrees C) and later during cooling (back to 30 degrees C) compared with the PSE meat. 5. Freezing resulted in a trend of lower G' values before, during and after cooking. The results indicated that meat proteins were damaged during freezing and PSE meat was more severely affected, or that more protein denaturation occurred in the PSE meat.     

Effect of postmortem storage on mu-calpain and m-calpain in ovine skeletal muscle.

Casein zymography was used to determine the effect of postmortem storage on the proteolytic activity of mu-calpain and m-calpain in lamb longissimus. Casein zymography assays were conducted on crude muscle extracts (only one centrifugation). Six market weight crossbred lambs were slaughtered and a portion of the longissimus lumborum was removed at death (within 15 min of exsanguination) and after 3, 6, 9, 12, 24, 72, and 360 h postmortem. Muscle samples were snap-frozen in liquid nitrogen and stored at -70 degrees C. Soluble muscle proteins were extracted from muscle samples and analyzed by in-gel casein assay to measure calpain proteolytic activity. There was a gradual decline in mu-calpain activity (P < 0.05) such that after 24 and 72 h postmortem, mu-calpain had lost 42 and 95% of its activity, respectively. After 360 h postmortem, no mu-calpain activity could be detected (under the conditions used in this study). Autolysis of mu-calpain could be detected as early as 3 h postmortem. It was demonstrated that the detectable level of mu-calpain activity is a function of the amount of muscle protein electrophoresed. Hence, the activity data reported are in relative terms, rather than absolute values. Furthermore, it was demonstrated that the activity data also are a function of the assay methods used. Different methods have different lower detection limits. Of the three assays examined, 14C-labeled casein was the most sensitive, then the in-gel casein assay, and the least-sensitive method was the standard casein assay. Unlike mu-calpain, postmortem storage had no effect on m-calpain (P > 0.05). When the calcium concentration of a muscle extract was increased to the level that induces m-calpain autolysis, m-calpain was autolyzed and its autolysis was readily detected by the in-gel casein assay. Collectively, these results demonstrate that calcium concentration in postmortem muscle is only high enough to activate mu-calpain. These results support the widely believed conclusion that mu-calpain-mediated proteolysis of key myofibrillar and cytoskeletal proteins is responsible for postmortem tenderization. Hence, understanding the regulation of mu-calpain in postmortem muscle should be the focus of future studies.     

Selenium and zinc concentrations in kidney, liver and muscle of cattle from different parts of Norway.

Cattle slaughtered in four different parts of Norway have been examined with respect to selenium and zinc content in kidney, liver and muscle. Highest selenium concentrations were found in kidney and lowest in muscle. In spite of extensive use of standardized concentrates, geographic differences were detected with regard to selenium tissue levels, animals from the southeastern inland region having the lowest levels. According to other workers, this region has low-selenium humus soils, and selenium responsive diseases among young ruminants have been of considerable importance, especially when concentrates had not been given during winter feeding. The recorded tissue selenium levels are compared to other workers’ proposals for normal values. All animals examined in this study seem to be well within healthy limits. Kidney, liver and muscle from cattle are good sources of selenium with respect to human nutrition.As far as zinc concentrations are concerned, muscle has the highest and kidney the lowest levels. Geographic differences were found, and individuals from the midland and northern coastal regions have the highest zinc tissue levels. Cattle from the northern coastal region seems to have especially high zinc concentrations in the organs.     

Postmortem proteolysis and calpain/calpastatin activity in callipyge and normal lamb biceps femoris during extended postmortem storage.

The present experiment was conducted to determine whether calpastatin inhibits only the rate, or both the rate and extent, of calpain-induced postmortem proteolysis. Biceps femoris from normal (n = 6) and callipyge (n = 6) lamb was stored for 56 d at 4 degrees C. Calpastatin activity was higher (P < .05) in the callipyge muscle at 0 and 14 d postmortem, but not at 56 d postmortem. The activity of mu-calpain did not differ between normal and callipyge biceps femoris at 0 and 56 d postmortem (P > .05), but was higher at 14 d postmortem in the callipyge muscle (P < 0.05). The activity of m-calpain was higher in the callipyge muscle (P < 0.05). Western blot analyses of titin, nebulin, dystrophin, myosin heavy chain, vinculin, alpha-actinin, desmin, and troponin-T indicated that postmortem proteolysis was less extensive in callipyge than in normal biceps femoris at all postmortem times. The results of this experiment indicate that calpastatin inhibits both the rate and extent of postmortem proteolysis.