9:30 am - 10:30 am
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 Kristin Lee. This seminar is open to the general public to attend.
Meeting ID: 926 4443 4005
Thesis Topic: The genomic improvement of meat quality traits in pigs
MSc with Dr. Graham Plastow.
Meat quality traits are of increasing interest to the swine industry due to their influence on consumer purchasing and repurchasing decisions. However, meat quality traits must be measured post-mortem, meaning that these traits cannot be measured on the potential breeding candidates themselves, instead they must be measured on their siblings. For this reason, selection of meat quality traits using traditional selection methods is difficult, expensive, and not highly accurate, which is preventing the practical use of many of these traits in breeding programs today. Alternatively, genomic selection (GS) can be implemented for the improvement of meat quality traits. Using GS, breeding values are estimated using genomic relationships or genomic effects, resulting in a higher selection accuracy, and an increased rate of genetic gain compared to traditional selection methods. Therefore, genomic selection (GS) provides a significant opportunity to improve and predict better meat quality. The main purpose of this thesis was to improve our current understanding of the genetic and biological factors underlying meat quality traits in order to aid in the implementation of GS methods for meat quality traits. In part 1 of this thesis, variance component estimates were used to calculate genetic parameters for meat quality traits in pigs. This provided useful estimates of heritability for each trait, as well as insights into the genetic relationships between traits. These results could be used directly to incorporate meat quality traits into selection procedures, including both traditional or GS methods. Secondly, the biological factors underlying meat quality traits were explored. In part 2, a genome wide association study (GWAS) was used to identify quantitative trait loci (QTL) and genes associated with drip loss (DL). Following this, in part 3, a single-SNP association analysis was used to determine the effect of two potential causative mutations on meat colour phenotypes. These two analyses were intended to contribute to an improved understanding of the genes and mutations underlying meat quality traits, which would facilitate the future implementation of alternative methods of GS that incorporate biological knowledge. Phenotypes were collected from either a purebred Duroc (n = 997), or commercial crossbred pig population (Duroc X Landrace/Large White, n = 1098). Meat quality traits included various colour measurements (Minolta L*, b*, and a*) from multiple muscle types, including the longissimus dorsi (LOINL, LOINA, and LOINB), ham gluteus medius (GLUTL, GLUTA, GLUTB), ham quadriceps femoris (QUADL, QUADA, QUADB), and ham iliopsoas (ILIOL, ILIOA, ILIOB), as well as DL, and ultimate pH. In part 1 of this thesis, meat colour traits showed heritabilities ranging between low to moderate (0.06 to 0.44) and remaining meat quality traits showed moderate heritabilities, including DL (0.23±0.08) and pH (0.28±0.08). Moderate to high genetic correlations were observed between the same colour measurements from different muscle types (ranging between 0.50 to 0.96) and different colour measurements from the same muscle types (ranging between 0.56 to 0.92). Colour measurements also showed moderate to strong negative correlations with pH (ranging between -0.54 to -0.80) and positive correlations with DL (ranging between 0.38 to 0.69). The remaining meat quality traits, DL and pH, showed a strong negative correlation (-0.65±0.16). Overall, low to moderate heritabilities of meat quality traits shows that these traits can be improved by genetic selection methods (traditional or GS). Further, strong correlations between colour traits, as well as pH and DL show that improvements in one meat quality trait will cause similar changes to the corresponding trait. In the remaining studies of this thesis, parts 2 and 3, the biological factors underlying meat quality traits were explored. However, both studies proved to be underpowered in their ability to identify genes and causative mutations that were significantly associated with meat quality traits. Nonetheless, the results from these studies provide a basis for which future work can build upon.