Pork quality is affected by many genetic or non-genetic factors, including the farm, transportation, slaughter and processing environment. Meat scientists have done a lot of research on these aspects. The quality and composition of meat can be greatly improved. Through the study of the genetic background of pigs, people realized that selecting and using genetic technologies are important for improving pork quality. In addition, DNA traits can be used to predict quality traits. 1 A geneticist believes that a gene can be defined as a major gene when the average difference between the corresponding characteristics of a homozygous gene's carrying and non-carriers meets or exceeds an apparent standard deviation. Genes with obvious effects can be detected by analyzing the phenotypic data of genetically isolated families. This method is called segregation analysis. Sellier et al. evaluated two important major genes that affected internal quality: fluoroalkylation and RN genes. 1.1 The halothane-sensitive halothane-sensitive gene is also known as the pig stress syndrome (PPS) gene. Christian (1972) determined that fluoroalkyl is associated with breeding stock. A single-gene variable was observed when the pig was injured due to stress. Eikelenboom (1974) found that halothane gas can trigger PPS. Later, many comparative studies on stress-negative and positive meat quality were conducted. Many studies have found that the main differences in meat quality are pH, color, and water-based properties. These differences in the two genotypes are directly related to the significant difference in the incidence of PSE, which can be explained by different aspects of muscle metabolism. In fact, in stress-positive pork, the area of ​​muscle fibers is larger and capillary tension is reduced (Karlstorm et al., 1992). Pommier et al. found that PSE is not a direct result of fluoroalkylation, but fluoroalkylation often exacerbates PSE. Since 1991, we have been able to use the Hall843TM1 DNA test to accurately isolate three types of fluoroalkyline Fujii found that spontaneously generating PSS in genes encoding a rapidly vibrating fiber receptor isoform or calcium ion release channel. As long as we can easily detect heterozygous animals, we may do more detailed work on this mutation. At present, it is mainly discussed whether it is important for people to accept the meat quality of animals that carry this gene compared to animals that do not contain this gene at all. This is important because fluoroalkyl can significantly increase the lean body mass of the carcass but reduce the tenderness of the meat. Degree and juicyness. The best way depends on the slaughter conditions and processing methods. For breeding organizations, the best strategy is to ensure that the mother of slaughtered pigs is fluoroalkyl-negative, and that the parent's halothane status can be adapted to specific carcass needs. 1.2 The concept of the RN-gene RN gene was proposed by Naveau. The expression results in "acidic pork", which was later confirmed in a population segregation assay conducted in two French pigs of different strains, and is a dominant gene. The gene is named after Rendement Naploe (RN). The RN test is an experimental method for predicting the output. By reducing the protein content in the inner and lowering the final pH, this dominant allele results in a decline in technical quality. The decrease in the final pH is the result of an increase in the glycogen content in the white fibers. For example, during the thermal processing of low-phosphorus ham, the production of RN gene carriers is relatively low by 3% to 5%, and these ham meat may cause very serious slice loss. Until now, it was found that this gene was only isolated from the population affected by Hampshire. However, due to the dominant inheritance of genes and the widespread use of Hampshire boars, breeders are very concerned about this gene. Milan et al. found that the RN gene is located on chromosome 15. The recently published research results locate the RN gene on Sw2053-Sw936, approximately 8 cM fragments. Based on the position of the RN gene on the genetic map, a commercially available DNA marker was developed to detect the RN gene. This test successfully predicted the ultimate difference in pH and thermal processing output of the phosphorus-containing ham. The results of this study also show that when phosphates are used, there is no such difference. Although the DNA marker test is an excellent tool for reducing the range of RN gene influence, a DNA probe is also needed to detect spontaneous mutations to completely eliminate the effects of the RN gene. Milan more precisely mapped the RN gene and discovered several new markers that help eliminate this effect. 1.3 Intramuscular fat (lMF) It is believed that the IMF plays an important role in the taste of meat. Janss used a F2 hybrid of Meishan and a Dutch pig to analyze the meat quality and detected a recessive IMF gene derived from the Meishan pig breed. The IFM content in the psoas muscle with double copy IMF gene was 3.9%. The heterozygote of the IMF gene and the homozygous animal that does not carry the lMF gene contained only 1.8%. At the same time, the existence of IMF genes in Duroc purebred pigs was also studied. These research efforts may eventually lead to testing of DNA levels, and DNA testing allows people to better control the level of pork marble. The heritability of this trait is 50% and breeders will have a tremendous impact. But the real challenge is to obtain a higher IMF without increasing other fat deposition levels. 1.4 Androstenone Another characteristic of high heritability is the level of androsterone. Androstenone is one of the factors leading to castration of boars. Using separation analysis, Fouilloux et al. found a gene that controls androsterone levels. This gene, which causes a decrease in the level of androsterone, is dominant, and the level of androsterone in this gene carrier is 3 SD units lower than in non-carriers. At the same time, a gene that leads to a faster development of the urethral acini was also found. The size of these glands is considered a good indicator of sexual maturity in boars. Earlier studies in the French showed that there was a gene that affected the level of androsterone in the offspring of Meishan and Dabai hybrids. The effect of this gene on androsterone levels was associated with porcine histocompatibility antigen (SLA), and Rothschild et al. also found a link between SLA haplotypes and male development. Not only does androsterone cause castration infection, but 3-methyl hydrazine can also cause castrate infection. However, there are few genetic studies on 3-methylanthraquinone, but this feature also shows some genetic differences. According to a study of Yorkshire pigs, Lundstrom et al. believe that the genetic effect of 3-methylanthraquinone is influenced by a recessive gene. They estimated that the expression of this gene may depend on a specific environmental condition, such as dietary structure and hygiene. 1.5 Muscle fiber characteristics Different subfamilies of different expression of myofibrillar isoforms with different types and levels of metabolic enzymes and different ATPase activities eventually led to significant differences in muscle fiber types. The different myosin heavy chain isomers are encoded by genes that are separated from each other. Under different conditions, these genes have different priority levels of expression. Some genes are preferentially expressed in fast bone-type muscle and some genes are preferentially expressed in slow bone-type muscle. The amount of muscle fibers is innately determined, so the maximum availability of muscle fibers in meat products is determined at the time of embryonic muscle formation. Embryo myogenesis is under genetic control of the MyoD gene family. According to Fiedler et al.'s study and later Larzul- et al.'s study, test methods for muscle fiber characteristics (eg, fiber type distribution, etc.) can be used as a selection method because these characteristics are moderately inherited and are related to lean meat growth and meat quality. Sex. Recent research by Brocks et al. showed that the content of type IIB fibers was higher in the leaner lines. The pig's feeding process includes the choice of meat quality. Barton-Gade made a five-year survey of the internal quality of four Danish pigs and found that there was a tendency for flesh to decline. Barton assumed that this trend is caused by a change in the composition of the fiber, that is, an increase in muscle glycogen content. Similarly, the frequency of low tremors in the genetically improved Landrace White pigs was reduced by 5 percentage points compared to the previous Danish Landrace pigs, and tenderness was also reduced. 2 DNA technology The basis for the existence of the major genes mentioned above was obtained through separation analysis and did not involve DNA markers. Later, molecular level studies were performed to detect the location of these genes on the genetic map. In practice, in addition to some alleles with very obvious effects, the analysis of the genetic nature of important economically significant traits requires the study of DNA levels. The city will review the results of recent research on DNA tagging technologies that are closely related to genes and target gene mutations that are called candidate gene methods. 2.1 DNA Marking Technology Marking techniques can locate genes in genetic maps that dominate quality features such as appearance color. It can also be used to detect genes that have a substantial effect on quantitative characteristics such as growth rate, IMF, and the like. The application of DNA markers in this area is called Quantitative Trait Locus map-ping. In pig studies, QTL methods are commonly used in hybrid pigs such as Dabai and Meishan pigs. In fact, this method has been used to explain genes related to IMF. Janss et al. used a microsatellite identification method to determine the QTL after using a segregation analysis to identify an IMF master gene. Recently, they reported finding evidence that the IMF master gene was linked to some marker sites on chromosome 1 and one marker on chromosome 3. The same region with chromosome 1 was found in the back tick QTL. The team's final analysis identified the presence of IMF QTs on chromosomes 4 and 7. A recent study of the offspring of the cross between Liberian pigs and Landrace pigs revealed a QTL located on chromosome 6. A large number of pigs are now used or modified to search for meat quality QTLs. These pigs include: Dabai, Meishan and Changbai. The trait indicators include carcass composition, fat, lean meat distribution, and meat quality indicators such as hydrophilicity, shear force, IMF content, and flavor. The initial measurements in this regard were published by Andersson-Eklund et al. These data are based on studies of wild boar and Landrace hybrid strains. They did not find any meat-quality QTLs reaching the minimum standards of a significant genomic category. However, some important QTLs for carcass characteristics, such as psoas muscle area and lean meat rate, were found. The largest QIL is located on chromosome 4 and has a significant effect on the QTL and the rate of birth. Although QTLs have now been successfully detected, such as the backfat on chromosome 4, the level of fat males on chromosome 7, and the meat composition on chromosome 6. However, the application of these in commercial breeding programs is not meaningless. Many researchers in this area believe that it is necessary to confirm the genes in the QTL. This is a daunting task because the QTL is relatively large and contains many genes. Therefore, although the development of improved maps allows us to have more and better reference information from “rich†species such as humans and mice, there is still a huge obstacle in determining the genes associated with keeping animals. Therefore, the short-term task can only be how to apply the newly discovered QTL to commercial farming. For example, the goal of EC Bioengineering's pigQTech is to help the farmer make use of genomic map information to draw working drawings. Another aspect of the above method is the use of markers to convert beneficial QTLs present in non-commercial pigs (such as wild boars) into commercial pigs. In this regard, some of the findings of the PIGMap group regarding the recitation of QTLs merit attention. They confirmed a QTL located on chromosome 7. In Meishan pigs, the QTL region is represented by the lean meat allele, while in the white giant it is represented by the fat allele. This type of different effect also exists in some plants. This is a very useful discovery. It helps us to use some new technologies to control meat quality. 2.2 Candidate genes Candidate gene methods are relatively more direct than QTLs. For example, we use the polymorphisms in the candidate genes to explore the links between animals. Once this link is confirmed, the results can be directly applied in the breeding program. This method has been very successful in the study of estrogen receptor genes and litter size. The study of the heart fatty acid binding protein (HTABP) gene is an example of the application of the candidate gene method in meat quality. Grebens, et al. (1997) found polymorphisms in the H-FABP gene in Duroc pigs, and this polymorphism is associated with changes in the IMF. The H-FABP gene is located on chromosome 6 but not within the QTL region identified by De Koning, et al. (1998). A comparison of their homozygous haploid gene clusters revealed that they were on average about 15% different. Recently, the team found that the FABP4 gene has a very large influence on the lMF. In addition, this effect seems to have nothing to do with back fat. Therefore, the use of logo-assisted selection can provide people with the hope of controlling the IMF. At present, there has been a combination of candidate gene markers and QTL analysis, resulting in a joint analysis method. Now, people are very interested in whether the variants of IMF in hybrid pigs can be explained more perfectly. Another candidate gene approach is the study of calcium-activated proteases, calcium-dependent proteases and calcium cathepsin (B, B+L, H). At present, there are many studies on the number of calcium-activated proteases, the calcium-dependent protease system, and the role of these enzyme inhibitors cathepsins in cattle and sheep, including changes in protein in vivo and post-mortem Koohmaraie (1996). Excitingly, Ernst et al. reported that three polymorphic sites of the pig's cathepsin gene have been identified. There are also many ongoing studies on the genetic effects of cathepsin activity, which have a very important role in protein hydrolysis of products. Many studies have been made on the effect of porcine genes on calcium cathepsin B and B+B. This has an important role in protein hydrolysis in seasonal products. Relative to the Belgian Landrace pig series, higher calcium cathepsin B and B+B activity was now found in Great White pigs in England and the Netherlands. On the other hand, it was also found that the activity of calcium cathepsin H in Belgian Landrace pigs was higher than that of Duroc pigs, Great Britain pigs in the UK and the Netherlands. There was no significant difference in the activity of cathepsin B among the various groups, but there was a huge difference between the mutants within the population, and these differences had a certain degree of inheritance (0.23 to 0.28). Another candidate gene-based labeling method is myogenin (which increases the amount of muscle fibers that can affect the quality of pork in general) and the dominant KIT gene that causes white coat color in pigs. One of the disadvantages of candidate genes is that there are more and more genes, because more and more genes have been identified. For example, in the descriptions of Hwang, Loftus, Mandrup, and Lane, at least 30 genes have an effect on adipose tissue. DNA technology offers people a great opportunity to improve meat quality. The selection of a dominant gene will not only increase the average quality of meat, but will also reduce the mutation rate and maintain a stable genetic quality. On the other hand, the use of master genes can meet different market needs.
Others Pharmaceutical And Medical
Bisoprolol Fumarate,Trilostane Powder,Canagliflozin Hemihydrate
Pharmaceutical and Medical Co., Ltd. , http://www.chphmedical.com