1:30 pm - 2:30 pm
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Theresa Lantz. This seminar is open to the general public to attend.
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Thesis Topic: A genetic investigation of pork fat and its role in meat quality
MSc with Dr. Graham Plastow
Excellent pork meat quality for improved eating experience is becoming increasingly more important to consumers and therefore the hog industry as a whole. One of the most interesting factors associated with eating experience is fat; fat plays a significant role in the acceptance (and rejection) of pork. Two depots of fat which significantly affect the industry are intramuscular fat (IMF) and backfat; IMF plays an important role in eating quality (tenderness, juiciness) and the backfat depth (BFD) ultimately determines the lean yield of the entire carcass, which is used for its valuation and producer payment. Therefore, the main objective of this study was to investigate the genetic underpinnings of IMF as well as its relationship to backfat, due to their economic relevance and importance for producers, consumers, and the whole industry. In the first study, longissimus dorsi and backfat samples from 997 purebred Duroc gilts were analysed with near-infrared spectroscopy (NIR) in order to generate IMF and backfat composition phenotypes for further use in genetic studies. Resulting phenotypes were compared against reference methods to determine accuracy. The IMF phenotypes had a high degree of accuracy between the reference method and predicted phenotypes (p <0.0001). Backfat composition phenotypes had a low degree of accuracy from the NIR algorithm when compared to the reference method values (p <0.0001). The variance components of IMF and backfat, measured by various collection methods (NIR, ultrasound, subjective, traditional), were estimated in the second study in order to better understand the relationship between IMF and BFD. Crossbred animals were investigated in addition to the purebreds; phenotypes from a total of 916 crossbred (Duroc × [Large white × Landrace]) pigs were used and 997 purebred Duroc gilts were used. Heritability estimates (±SE) for IMF were moderate-high (0.38±0.09) in the purebreds and moderate in the crossbreds (0.24±0.07); heritability estimates (±SE) for backfat were high in the purebreds (0.46 0.09) and crossbreds (0.49 0.09). There were moderate-high positive genetic correlations between IMF and BFD for all measurement methods in the purebreds (0.36 0.14) and crossbreds (0.44 0.63). This indicates that IMF and BFD are good indicator traits for one another; that the selection of one would also select for the other. There was a high positive coefficient of correlation between NIRIMF and ultrasound IMF (UIMF) as well as BFD and ultrasound backfat thickness (UBFD) which indicates that the method of phenotype collection could be substituted for the other and maintain similar accuracy in further studies. Finally, three genome-wide association studies (GWAS) were conducted with IMF phenotypes from the purebred Durocs (UIMF, NIRIMF) and commercial crossbred pigs (UIMF) in order to investigate the genetic underpinnings of IMF. From this, five significant single nucleotide polymorphisms (SNPs) were identified in the purebred Durocs with association with IMF. No significant SNPs were identified in the crossbreds from GWAS; after application of an additional statistical method (LASSO) three SNPs with measurable effect size were identified. With further validation, the findings in these studies will help increase understanding of the genetic underpinnings of IMF and aide its independent manipulation from backfat. The findings from all studies can be utilised as reference for the hog industry to help develop novel genomic tools to identify animals with superior meat quality and improve Canadian pork.