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Impact of Genetics on Meat Quality of Pigs and Beef Cattle

  • Author / Creator
    Lei, Huaigang
  • Meat has changed its role from just providing necessary nutrition for the human body to improving the quality of life by giving us eating satisfaction, resulting in the impetus for scientific research on meat quality. Although many strategies have been taken to improve meat quality, unacceptably inferior meat still exists, causing economic loss for the meat industry. Potentially, improving meat quality through animal breeding offers opportunities to obtain superior meat. Hence, to explore the possibility of future genetic selection of animals for meat quality, several studies investigating different meat quality traits, different species, and different sample handling strategies were conducted. Dark cutting beef is a significant defect caused by depletion of muscle glycogen before slaughter that may be affected by animal genetics. A case-control genome-wide association study (GWAS) on two groups of beef cattle was conducted and dark-cutting was analyzed as a binary trait (cases versus controls) using logistic regression in an additive model. There were no significant loci identified when correcting for multiple testing (false discovery rate, FDR) using a FDR < 0.05 threshold. The regions with the strongest support for association with the occurrence of dark cutting were identified using a 1 MB window and functional analysis using the Ingenuity Pathway Analysis (IPA), which identified genes involved in pyruvic acid modification, 2-deoxyglucose clearance and disposal, pyruvic acid release, sucrose recognition, energy production and metabolism of carbohydrate. Although the detected SNP associations require validation, results suggested the possibility for marker-assisted genomic selection of beef cattle for reduced likelihood of dark cutting; however, based on these results a much larger number of case samples will be required to validate these observations Consumer willingness to pay a premium when purchasing pork chops is driven by eating satisfaction. Genetic parameters were estimated for loin muscle sensory traits within a swine population and their associations with loin pH and intramuscular fat were analyzed. Animal pedigree and genotype information were analyzed separately, and positive genetic correlations between sensory measurements and pH and intramuscular fat were found, indicating that selection for intermediate pH and high intramuscular fat can help to increase sensory scores. However, as the genetic correlations were moderate to low, increase in pork sensory scores through selection for loin pH and intramuscular fat content would be slow. Important meat quality characteristics have been measured on fresh and previously frozen meat as part of previous genetic studies, but freezing may alter meat quality characteristics and therefore the relationships between genetic components and meat quality measurements. Results showed that pork quality traits measured before and after freezing and thawing were significantly (P<0.0001) different from each other and that intramuscular crude fat content exerted a large effect on the magnitude of change in L* (lightness) and b* (yellowness). Meat quality measurements of fresh pork were moderately to highly heritable except for b* and pH, with heritability estimates for L*, pH and drip loss higher when measured on fresh rather than frozen-thawed samples. Considering heritability and genetic correlation results, it could be concluded that whilst either fresh or frozen-thawed pork samples can be used for L*, a* (redness) and b* measurements can be used in genetic selection, pH and possibly drip loss should be measured in fresh pork samples rather than in those that have been frozen-thawed. Tenderness is one of the most important factors considered by consumers when purchasing meat and intramuscular connective tissue (IMCT) is a major factor responsible for the cooked meat background toughness. A GWAS was designed to identify variations (e.g.: single nucleotide polymorphisms (SNPs)) in genes along the genome associated with total collagen and collagen solubility. In total, 130 SNPs were detected for 3-day postmortem (3 dpm) total collagen content using SNP windows that explained more than 1% of the additive genetic variance, while 160 SNPs were detected for 3 dpm collagen solubility, and 150 and 190 SNPs were detected for 13 dpm total collagen content and collagen solubility, respectively. These results should be validated in a large beef cattle group before considering marker-assisted or genomic selection in beef cattle to increase beef tenderness. Collectively these results indicated that selection against dark cutting and for increased collagen solubility in beef, and for increased pork acceptability may be possible.

  • Subjects / Keywords
  • Graduation date
    Fall 2019
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-f6p3-2590
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.