猪肌纤维生长发育的影响因素及调控机理

肌纤维是构成骨骼肌的基本结构单位，其纤维类型在机体发育过程中受内因和外因的相互作用发生转化，而肌纤维特性与肉色、持水性能、pH和脂内脂肪含量等肉品质有关，直接决定畜禽肉品质的好坏。因此，近年来肌纤维的生长发育成为研究热点。本文主要对影响猪肌纤维生长发育的因素及调控通路进行综述，以期为猪肌纤维类型及其转化的研究提供理论参考。     

深州猪、汉沽黑猪和大约克夏猪肌肉组织学特性的研究

本文对深州猪、汉沽黑猪和大约克夏猪背最长肌的单位面积内肌纤维所占比例、肌纤维横截面积、肌纤维密度以及眼肌面积和瘦肉率进行了研究。结果如下:①深州猪单位面积肌纤维所占比例明显小于汉沽黑猪和大约克夏猪;②深州猪肌纤维横截面积大于汉沽黑猪和大约克夏猪;③深州猪、汉沽黑猪和大约克夏猪的肌纤维密度差异不显著:④眼肌面积和瘦肉率以大约克夏猪为最大,汉沽黑猪次之,深州猪最小。     

猪肌肉肌纤维类型组成的影响因素研究进展

成年哺乳动物骨骼肌肌纤维类型根据肌球蛋白重链（MyHC）基因的多态性表达可分为MyHCⅠ、Ⅱa、Ⅱx和Ⅱb 4种类型。肌纤维类型在内因与外因共同作用下会发生转化，进而改变肌纤维类型组成。肌纤维类型组成与肌肉品质有着密切关系。肌纤维类型组成不同，宰后肌肉感官品质不同，感官品质进一步决定肌肉的风味及口感。猪是重要产肉经济动物，深入了解影响猪肌肉肌纤维类型组成的因素有助于人们对猪肌肉品质进行有效调控。文章综述了遗传、生长阶段、环境温度、营养、添加剂等因素对猪肌肉肌纤维类型组成的影响。     

猪肌纤维类型与肉品质特性及影响猪肌纤维类型转化的研究进展

肌纤维是构成肌肉组织的基本结构单位,其类型组成与pH、肉色、嫩度和肌内脂肪含量等猪肉品质指标密切相关,且肌纤维类型在生长发育、营养因素和环境因素等条件下会发生转化,进而影响猪肉品质。近年来对肌纤维类型及其转化的研究逐渐成为热点,本文综述了猪肌纤维类型与肉品质特性及影响猪肌纤维类型转化的因素,以期为猪肌纤维类型及其转化的研究提供参考。     

莱芜猪和鲁菜黑猪肌纤维发育规律及其对肉质特性的影响

本研究以40～90kg6个体重阶段的莱芜猪和鲁莱黑猪为试验对象,每个阶段每组各6头猪,采用组织化学切片染色技术进行组织学观察,探讨猪肌纤维的发育规律及其对肉质特性的影响。结果表明：①随着体重的增加,莱芜猪与鲁莱黑猪肌纤维的发育较为明显,但发育特点明显不同,莱芜猪40～70kg体重时肌纤维生长较慢,直径和面积变化不明显,70kg后肌纤维生长发育明显加快（P〈0．05）;而鲁莱黑猪则是40～60kg体重时肌纤维生长较快,60奴后肌纤维生长发育变慢（P〈0．05）。（爹琥珀酸脱氢酶（sDH）组织化学处理显示,肌肉肌纤维是由红肌纤维、中间型肌纤维和白肌纤维这3种类型肌纤维构成,并以白肌纤维占优势。莱芜猪与鲁莱黑猪在肌纤维类型的组成和不同类型肌纤维直径上具有不同的发育性变化模式,总体上莱芜猪红肌纤维含量有高于鲁莱黑猪的变化趋势。在不同类型肌纤维直径方面,莱芜猪与鲁莱黑猪具有基本相同的发育性变化模式。③相关性分析表明,肌肉的肌纤维尤其是红肌纤维的生长发育,对肌肉的干物质、肌内脂肪及系水力等肉质性状具有有利的影响,但白肌纤维的生长发育对肌肉的系水力具有不利的影响。研究结果提示：在肌肉组织中肌纤维的发育方面,莱芜猪比鲁莱黑猪较为晚熟;在肌纤维类型的组成方面。红肌纤维更有利于优良肉质特性的形成。     

长白猪北京黑猪及民猪肌肉组织学特性研究

长白猪北京黑猪及民猪肌肉组织学特性研究王楚端，陈清明（中国农业大学动物科技学院北京１０００９４）前言肌纤维组织学特性对肉质具有重要影响。肌束内肌纤维数目是判定由质细嫩致密与否的重要因素，无论屠宰活重或日龄大小，都是以肌纤维越细者，肉质越鲜嫩（川井田博...     

品种、体重和营养对猪背最长肌肌纤维组织学特性的影响

选用荣昌(RC)猪和杜×长×大(DLY)杂交猪为试验对象,研究猪背最长肌肌纤维直径和密度的发育性变化及品种与营养影响特点。结果表明:2个品种猪的背最长肌肌纤维直径和密度的发育规律较为类似,肌纤维直径随体重增加呈线性增长,而肌纤维密度则随体重增加呈乘幂方程式降低。相关分析表明,肌纤维密度与直径均存在极显著负相关(P≤0.003)。背最长肌肌纤维直径和密度在20～50kg阶段品种间差异不显著(P≥0.099),但在80kg,RC猪的肌纤维直径显著低于DLY猪(P=0.0043),而RC猪的肌纤维密度则显著高于DLY猪(P=0.0049)。饲粮营养水平对2个品种猪背最长肌的肌纤维直径和密度均无显著影响。以上结果提示,2个品种猪的背最长肌肌纤维的生长规律较为类似,但不同品种的肌纤维直径存在差异,主要表现在80kg,RC猪显著低于DLY猪,可能与其优良肉质有关。     

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。     

运输应激对2种Hal基因型猪肌纤维特性的影响

以二花脸与皮特兰杂交F2代猪为研究对象,应用组织学、组织化学方法与电镜技术研究运输应激对2种猪背最长肌琥珀酸脱氢酶(SDH)、乳酸脱氢酶(LDH)、糖原以及肌纤维超微结构的影响,并分析比较了2种氟烷基因(HalNN,Halnn)猪背最长肌各肌纤维类型。研究发现:(1)HalNN猪背最长肌SDH活性比Halnn猪的极显著高(P<0.01);(2)背最长肌LDH活性Halnn猪比HalNN猪的极显著高(P<0.01);(3)Halnn猪糖原含量比HalNN猪的显著高(P<0.05);(4)透射电镜显示HalNN猪背最长肌肌纤维超微结构形态较清晰完整,而Halnn猪肌纤维收缩剧烈,肌节混乱,明带暗带区分不明显,有的肌节甚至降解,线粒体不同程度肿胀和裂解,肌浆网不明显等。结果表明:氟烷基因野生型HalNN猪对运输应激相对不敏感;而阴性纯合子Halnn猪则对应激很敏感,其肌纤维损伤较大。     

江山乌猪种质特性研究

本研究系统测定了江山乌猪的体重、体尺、育肥性能、繁殖性能、屠宰性能和肉质性状等主要的种质特性。经过分析，江山乌猪的优势特点总结为肌纤维直径小（36.75μm）、肌纤维密度大（512.86根/mm2），肌内脂肪含量比例适中（4.30%），不饱和脂肪酸特别是多不饱和脂肪酸含量高（阉公猪14.08%，母猪12.92%）。本研究完善了江山乌猪的种质性能资料，为江山乌猪遗传资源的保护和开发利用提供了参考依据。     

高通量转录组测序技术在猪肉品质研究中的应用进展

猪肉中基因的表达决定了蛋白质的种类、结构和功能,从而决定了肉品质,而肌内脂肪(IMF)和肌纤维(MF)是影响肉品质的关键物质。本文主要综述了高通量转录组测序技术在研究猪肉品质相关的IMF和MF转录组的应用,重点阐述了其研究进展。     

不同施肥模式对玉米各器官碳氮累积和分配的影响

以长期定位试验为依托,选取:1)不施肥(CK);2)农民习惯施肥(FP);3)推荐施肥(OP);4)有机肥氮替代100%化肥氮(OM);5)有机肥氮替代50%化肥氮(MF)5个处理,研究不同施肥模式对玉米植株及各器官碳氮含量、碳氮分配比例及C/N的影响,为西南紫色土地区合理施肥、作物增产提供科学依据。结果表明,与FP处理相比,MF处理显著增加了玉米植株生物量,达26.2%。相比OM和OP处理,MF处理显著增加玉米苞叶和根茬中碳浓度,分别增加5.4、4.2 g·kg^-1和7.4、21.3 g·kg^-1,同时增加玉米苞叶、根茬、穗轴和籽粒中的碳储量,玉米茎秆和籽粒中的氮储量也有增加。此外,相比FP处理,MF处理能显著增加玉米整株的碳储量和氮储量,达29.1%和16.9%。等氮水平下,MF、OP处理均能增加玉米苞叶和籽粒中碳同化物的分配比例,MF处理玉米籽粒中氮素的分配比例较OP和OM处理分别增加1.7%和3.6%,同时MF处理能使玉米维持较高的C/N。综上,有机肥氮替代50%化肥氮能增加玉米植株的生物量,同时提高玉米对氮素的吸收和碳素的累积,增加玉米籽粒中碳同化物和氮素的分配比例,同时,有机肥氮替代50%化肥氮能使玉米植株维持较高的C/N,有利于产量的形成,该施肥方式不仅能够促进氮素的高效利用,减少化肥的投入,还能够减少化肥损失,降低氮素损失引发的环境风险。     

Fuzzy comprehensive evaluation on the quality of different mixed feeds for fattening lambs by using in vitro method

Fuzzy comprehensive evaluation and in vitro methods were used to rank nutritive quality of 15 mixed feeds (MF) formulated for fattening Tan-sheep weaned lambs, a breed distributed in northwestern China. In vitro parameters of neutral detergent fibre digestibility (NDFD), volatile fatty acids (VFAs) and ammonia nitrogen (NH₃–N) were used as evaluation parameters. Each MF consisted of alfalfa meal, bio-chemical treated maize stover and grain mix. The relative proportions of alfalfa meal:bio-chemical treated maize stover:grain mix (dry matter (DM) basis) was 10:50:40 (MF1), 20:40:40 (MF2), 30:30:40 (MF3), 10:45:45 (MF4), 20:35:45 (MF5), 30:25:45 (MF6), 10:40:50 (MF7), 20:30:50 (MF8), 30:20:50 (MF9), 10:35:55 (MF10), 20:25:55 (MF11), 30:15:55 (MF12), 10:30:60 (MF13), 20:20:60 (MF14) and 30:10:60 (MF15). Values of each observed parameter were differed significantly among the tested feeds (p < 0.05). Greater NDFD, AA, PA, BA and NH₃–N were observed for the MF9, MF14, MF2, MF11 and MF7 respectively, which indicated the associative effects between feeds constituents (e.g. concentrate, bio-chemical treated maize straw and alfalfa powder). The fuzzy comprehensive evaluation value of MF7 was the highest in the 15 mixed feeds, which indicated that the incubation effectiveness of MF7 was the best among the 15 mixed feeds when its roughage to concentrate ratio was 500 to 500 g/kg with roughage constituents of 400 g/kg bio-chemical treated maize stover and 100 g/kg alfalfa meal. It was concluded that fuzzy comprehensive evaluation is a useful tool for comprehensively considering the in vitro parameters of mixed feeds to rank the nutritive quality in terms of nutrient supply potential.     

Effects of allergen challenge on plasma concentrations of prostaglandins, thromboxane B2, and histamine in calves infected with bovine respiratory syncytial virus.

To examine the influence of allergen-induced type-1 hypersensitivity on the pathogenesis of bovine respiratory syncytial virus (BRSV) infection, we sensitized calves by aerosol to Micropolyspora faeni (MF) and challenge exposed them during infection with BRSV. The development of MF-specific IgE serum concentrations was confirmed by ELISA. The dynamics of arachidonic acid metabolism and histamine release during a type-1 hypersensitivity reaction in the bovine lung were studied by quantitating the concentrations of prostaglandin (PG)E2, PGF2 alpha, PGI2 as 6-keto-PGF1 alpha, thromboxane (TX) A2 as TXB2, and histamine in plasma of BRSV-infected and/or MF-sensitized/challenge-exposed calves. Four treatment groups were established: (1) BRSV infection only, (2) aerosol sensitization to MF followed by BRSV infection and aerosol challenge exposure to MF, (3) MF aerosol sensitization and challenge exposure without BRSV infection, and (4) aerosol sensitization to MF followed by BRSV infection without MF challenge exposure. Significantly increased concentrations of PGI2 were associated with MF aerosol exposure, particularly when combined with BRSV infection in group 2. After MF challenge exposure, TXB2 concentrations were significantly greater in the virus and MF challenge-exposed group 2. Individual calf data for the change in MF-specific IgE concentration between the first and second MF challenge exposures and the change in PGE2 concentration 30 minutes after the second MF challenge exposure had a highly significant direct correlation. Histamine concentrations were significantly greater in calves infected with BRSV than in uninfected controls regardless of MF exposure. These data further substantiate the thesis that implicates type-1 hypersensitivity as a pathogenic mechanism in BRSV-related disease.     

Characterization of the serum metabolic profile of dairy cows with milk fever using 1H-NMR spectroscopy

Background: Milk fever (MF) is a common calcium metabolism disorder in perinatal cows. Currently, information regarding the detailed metabolism in cows suffering from MF is scant.

Objective: The purpose was to study the metabolic profiling of serum samples from cows with MF in comparison to control cows, and thereby exploring other underlying pathological mechanisms of this disease.

Animals and methods: In the current study, we compared the serum metabolomic profile of dairy cows with MF (n = 8) to that of healthy dairy cows (n = 24) using a 500-MHz digital ¹H-nuclear magnetic resonance (¹H-NMR) spectrometer. Based on their clinical presentation and serum calcium concentration, cows were assigned either to the control group (no MF symptoms and serum calcium concentration >2.5 mmol/L) or to the MF group (MF symptoms and serum calcium concentration <1.4 mmol/L). For statistical analysis, a one-way analysis of variance was performed.

Results: We identified differences regarding nine metabolites between the two groups, among which glucose, alanine, glycerol, phosphocreatine, and gamma-aminobutyrate decreased, and β-hydroxybutyrate, acetone, pyruvate, and lysine increased in cows with MF. Most of these were carbohydrates and amino acids involved in various energy metabolism pathways.

Conclusion: The different metabolites in cows with MF reflected the pathological features of negative energy balance and fat mobilization, suggesting that MF is associated with altered energy metabolism.

Clinical importance: The ¹H-NMR spectroscopy can be used to understand the pathogenesis of MF and identify biomarkers of the disease.     

Investigation on the association between atopic dermatitis and the development of mycosis fungoides in dogs: a retrospective case-control study

In human medicine, the relationship between the immunodysregulation observed in atopic dermatitis (AD) and the development of mycosis fungoides (MF) has triggered considerable interest due to the increasing number of patients with MF who have a previous history of AD. The purpose of this retrospective case-control study was to investigate whether dogs diagnosed with MF were more likely to have AD. The records of 96 000 canine patients at the University of Florida were searched. Inclusion criteria were a clinical and histological diagnosis of MF. Dogs admitted to the University of Florida, Veterinary Medical Center during the same time period (1991-2004) without a diagnosis of MF were included as controls. Four controls for each study dog were randomly selected (matched by year of admission). Frequency of AD and other exposure variables were compared among case and control dogs by using conditional logistic regression. Records of 19 dogs with a diagnosis of MF were identified. Five of them (5/19, 26.3%) had previous diagnosis of AD. The odds of having MF was 12 times (OR = 12.54; 95% CI = 1.95-80.39; P < 0.01) higher in dogs with AD than in dogs without AD. In conclusion, this study suggests an association between AD and MF in dogs. Future studies are necessary to confirm this finding and to investigate the pathogenic mechanisms involved in this association.     

Supplementation with cumulus cell masses improves the in vitro meiotic competence of porcine cumulus–oocytes complexes derived from small follicles

The present study was conducted to examine the supplemented effect of cumulus cell masses (CCMs) derived from middle follicle (MF; 3–6 mm diameter) on the morphology and the meiotic or developmental competence of oocytes from small follicles (SF; 1–2 mm diameter). The number of cumulus cells surrounding oocytes just after collection was also lower in cumulus–oocyte complexes (COCs) from SF than MF. The ooplasmic diameter of oocytes was significantly smaller in SF‐derived oocytes than MF‐derived ones before and after in vitro maturation (IVM), whereas the diameter significantly increased during the culture. Co‐culture of SF‐derived COCs with MF‐derived CCMs during IVM significantly improved the meiotic competence of the oocytes to the metaphase‐II stage. Furthermore, the ooplasmic diameter of SF‐derived COCs during IVM was increased to the similar size of MF‐derived those in the presence of MF‐derived CCMs. The abilities of oocytes to be penetrated, to form male pronuclear formation and to cleave or develop to the blastocyst stage were not affected by the co‐culture with CCMs. Electrophoretic analysis of CCM secretions clearly showed the presence of more protein(s) approximately 27.6 kDa in the conditioned medium when supplemented with MF‐derived CCMs. In conclusion, we demonstrate that supplementation with MF‐derived CCMs improves the ooplasmic diameter and meiotic competence of SF‐derived oocytes.     

Influence of Dietary Metformin on the Growth Performance and Plasma Concentrations of Amino Acids and Advanced Glycation End Products in Two Types of Chickens

Glycation is a non-enzymatic reaction inducing the bonding of glucose to amino acids and proteins. Glycated amino acids are not useful for protein synthesis, suggesting that glycation reduces the utilization of amino acids. Metformin (MF) is well known as a therapeutic drug for type II diabetes that inhibits glycation. It is possible that treatment with MF raises the utilization of amino acids by the inhibition of glycation, thereby improving the growth performance of chickens. In the present study, therefore, we investigated the influence of dietary MF on the growth performance, and plasma concentrations of free amino acids and N^ε-(Carboxymethyl)lysine (CML), which is an advanced glycation end product, in layer (Experiment 1) and broiler (Experiment 2) chickens. From 7 d of age, chicks were allowed free access to one of the experimental diets containing MF at 3 supplementation levels (0, 150, and 300 mg/kg diet) for 14 days. Body weight and feed intake were measured every week. At the end of the experiments, blood and breast muscle (M. pectoralis major) were collected for further analysis. Dietary MF did not affect weight gain, feed intake, or feed efficiency in both layer and broiler chickens. Dietary MF at the level of 150 mg/kg diet increased breast muscle weight in both layer and broiler chickens. Dietary MF increased plasma concentrations of branched chain amino acids and decreased concentrations of CML in layer chickens, although it did not affect plasma concentrations of glucose. The present study suggested that dietary MF might have the potency to increase breast muscle weight of layer chickens with an increment in plasma concentrations of branched-chain amino acids.     

Quantitative feed restriction or meal-feeding of broiler chicks alter functional development of enzymes for protein digestion

1. Two experiments were performed on broiler chicks to determine the effect of either quantitative feed restriction (QFR) from 5 to 11 d of age or meal-feeding (MF) from d 5 to 17 on development of activity of enzymes associated with protein digestion. 2. Proteolytic activity of the proventriculus was reduced by QFR but unaffected by MF. 3. General proteolytic and carboxypeptidase A activities of the pancreas were reduced by QFR and MF. 4. Amino- and dipeptidase activities of the small intestine were increased by QFR. Dipeptidase activity was unaffected by MF. 5. Nitrogen retention of QFR chicks was lower immediately following feed restriction but not in the 2 weeks following return to ad libitum access to feed. 6. Feeding regimen alters functional development of the enzymes of protein digestion and may therefore influence growth rate of broilers.     

A stochastic model simulating milk fever in a dairy herd

A simulation model was developed to evaluate the long-term effect of control strategies against milk fever (MF); here, we present the base model and sensitivity analyses. The representation of the within-herd dynamics was based on the existing SimHerd II model. Because of the relationships between MF and other diseases, the new model (called “SimHerd III”) includes diseases common in a dairy herd.

The cow level risk factors modelled were: base risk in the herd, parity, milk-yield potential, lactational disease recurrence, disease interrelationships, body condition and season. The diseases include clinical cases of MF, dystocia, downer-cow syndrome, retained placenta, metritis, displaced abomasum, ketosis and mastitis. The effects of diseases were represented by daily milk yield, daily body weight, daily feed intake, risk of stillbirth, conception probability, decision on culling, death and immediate removal. Simulated technical results showed that the herd effects of reduced risk of MF differed according to the reproductive efficiency in the herd. These interactions between reproduction efficiency and the effect of reduced base risk of MF were related to differences in how the simulated herds reacted to the reduction in replacements caused by MF.

In the sensitivity analysis, eight potential key parameters were changed to their lowest and highest expected values retrieved from the literature. When measuring the sensitivity on milk production in the herd (as the economically most important technical effect), the model seemed most sensitive to the uncertainty of effect of MF on death risk and MF-recurrence risk.