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张春燕博士
Chunyan Zhang, PhD
阿尔伯塔大学研究所/加裕公司
Research Associate, University of Alberta / Genesus Inc.
对于猪肉行业，有一个共同的目标：为客户提供具有竞争力的成本，健康的，统一的高品质产品。客户的食用体验是影响他们购买决策的首要因素。猪肉食用品质大多数是和整体接受性，多汁性和嫩度相关联的，而嫩度被认为是客户满意度的最重要特征。因此，提高猪肉的嫩度对于猪肉行业非常重要，这样才能更好地满足那些喜欢有一贯的良好的食用体验的客户的需求。
For the pork industry, there is one common goal: to provide a cost competitive, wholesome, uniform and quality product to the consumer. The consumers` eating experience is a primary factor influencing their purchasing decision. Pork eating quality is mostly linked with the overall acceptance, juiciness and tenderness, with tenderness being considered the most important feature of consumer satisfaction. Therefore, improving pork tenderness is important for the pork industry so as to better satisfy consumer preference for a consistent and pleasurable eating experience.
嫩度评估通常是由训练有素的或者客户评审专家所做的评分结果。但是，这种评估方式不管评审团是经过训练的专业人士还是客户都会很贵，难于组织并且耗时。因此，评审专家们发明出了能够精确反应嫩度评分的仪器分析方法。沃-布式剪切力(WBS)是最常用的嫩度估测标准。它可以用于生肉，也适合商业应用。最近的一个报告表明WBS和评审专家嫩度评估变量都有着重要的和良好的相关性，这些变量包括柔软度(-0.18)，初始嫩度(-0.23)，咀嚼度(-0.27)，分解度(-0.26) (Choe et al., 2016)。
Tenderness evaluation usually is the result of scoring done by trained or consumer panelists. However, this kind of evaluation is expensive, difficult to organize, and time consuming, regardless of whether the panelists are trained professionals or consumers. Consequently, instrumentation methods that can accurately reflect the meat tenderness ratings generated by panels have been developed. Warner-Bratzler shear force (WBS) is the most widely used estimator of tenderness. It can used with raw meat and is suitable for commercial application. A recent report showed that the WBS has significant and favorable correlations with the panelist tenderness evaluation variables, such as softness (-0.18), initial tenderness (-0.23), chewiness (-0.27), and rate of breakdown (-0.26) (Choe et al., 2016).
有许多因素影响猪肉剪切力，当然基因是最重要的决定因素之一，能够解释剪切力中30%-40%(遗传可能性/遗传力)变化。(Ciobanu et al., 2011 and Miar et al., 2014).嫩度和许多其他肉质性状也是正相关的，比如大理石纹评分和肌内脂肪(0.32) (DeVol et al., 1988)。在过去几十年侧重选育瘦肉量(主要是减少脂肪厚)导致了大理石纹的减少，但是，大理石纹和脂肪厚的相关性小于1，因此有机会选育更多的大理石纹，在嫩度上有相关联的提高的同时也减少脂肪厚。
There are many factors influencing pork shear force, and of course genetics is one of the most important determinants that explains about 30% - 40% (heritability) of the variation in shear force (Ciobanu et al., 2011 and Miar et al., 2014). Tenderness is also positively correlated with many other meat quality traits, such as marbling score and intramuscular fat (0.32) (DeVol et al., 1988). The focus on selection for lean yield (mainly reduced backfat) in the past decades has resulted in a reduction in marbling, however, the correlation between marbling and backfat is less than one so there is opportunity to select for more marbling, and its associated improvement in tenderness while also reducing backfat.
客户要求猪肉有最小可见脂肪，即使这会食用体验不那么良好。遗传改良对于提高大理石纹和嫩度的同时减少脂肪厚起着重要的作用。但是，由于剪切力测量的高成本和死后可获得的猪肉品质数据量的有限性，仅采用传统育种方法很难满足客户这方面的要求。包括纳入到遗传改良体系中的基因组信息可以提供实现这一目的的好的解决方案。到目前为止，已经检测出了有大约191个基因组区域(QTL)用于控制剪切力的(PigQTLdb, 发布30,2016年8月29日)。最近，高密度SNP芯片(60K, 80K, 650K 以及甚至是整个SNPs宽序列)和改良的基因组方法已经被越加广泛地应用于识别猪肉嫩度方面更精确的标记(Nonneman et al., 2013; Zhang et al., 2016)。
Consumers demand pork with minimal visual fat even though it results in a less favorable eating experience. Genetic improvement can play a significant role in improving marbling and tenderness while reducing backfat. However, it is difficult to satisfy this consumer requirement using only traditional breeding methods due to the high cost of shear force measurement and the limited amount of pork quality data available post-mortem. Including genomic information into the genetic improvement program may provide a good solution to achieve this end. To date, about 191 regions of the genome (or QTL) have been detected for pork shear force (PigQTLdb, release 30, August 29, 2016). Recently high-density SNP chips (60K, 80K, 650K and even whole sequence wide SNPs) and improved genomic methods have been increasingly used to identify more precise markers for pork tenderness (Nonneman et al., 2013; Zhang et al., 2016).
加裕公司从1998年起开始进行胴体和猪肉品质项目。最近加裕对于猪肉品质的基因组研究识别出了在染色体2和17上的四个重要的SNP标记，它们对猪肉剪切力有重大影响。带有有利基因型的猪嫩度就会得到极大改善(剪切力减少)。如下图所示，对于染色体2上面的标记，带有BB基因型(有利)的猪的剪切力比带有AA基因型的猪的剪切力要低8个单元。所有我们期待带有BB基因型的猪可以改善客户的猪肉嫩度。最近，加裕公司能够应用SNP芯片来协助改善猪肉品质。我们也测试了采用基因组标记来改善嫩度和其他肉质性状的基因组评估的可行性。不断改进基因组技术并结合这些结果会提高加裕公司在猪肉品质方面的遗传改良体系，从而最终实现为加裕客户增加经济效益的最终目标。
Genesus Inc. has conducted a carcass and pork quality program since 1998. A recent Genesus genomic study on pork quality identified four important SNP markers on chromosomes 2 and 17 which significantly affect pork peak shear force. Animals with the favorable genotypes have significantly improved tenderness (decreased shear force). As shown in the figure below, for the marker on chromosome 2, pork shear force for animals with BB (favorable) genotype was about 8 units lower than that from animals with AA (unfavorable) genotype. So pigs with the favorable genotype (BB) are anticipated to improve consumer pork tenderness. Most recently Genesus Inc. can utilize SNP chips to assist in the improvement of pork quality. We also tested the feasibility of using genomic markers to improve the genomic evaluation for tenderness and other important meat quality traits. Incorporation of these results along with continual improvement of the genomic technologies will enhance the Genesus genetic improvement program for pork quality, and consequently enhance the ultimate goal of increasing profitability for Genesus customers.
参考文献清单
Reference list:
Choe, J. et al., 2016. Estimation of Sensory Pork Loin Tenderness Using Warner-Bratzler Shear Force and Texture Profile Analysis Measurements. Asian Australas. J. Anim. Sci., 29(7): 1029-1036
Ciobanu, D.C. et al., 2011. Genetics of Meat Quality and Carcass Traits. Genetics of the Pig, 2nd Edition: 355–389.
De Vol, D.L. et al., 1988. Variation in composition and palatability traits and relationships between muscle characteristics and palatability in a random sample of pork carcasses. J. Anim. Sci. 66 (2): 385-395.
Miar, Y. et al., 2014. Genetic and phenotypic parameters for carcass and meat quality traits in commercial crossbred pigs. J Anim Sci 92: 2869 - 2884.
Nonneman, D.J. et al., 2013. Genome-wide association of meat quality traits and tenderness in swine. J Anim Sci 91: 4043–4050.
Zhang, C. et al., 2016. Genome Wide Association Studies (GWAS) Identify QTL on SSC2 and SSC17 Affecting Loin Peak Shear Force in Crossbred Commercial Pigs. PLoS ONE 11(2): e0145082.
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