2:00 pm - 3:00 pm
318J Agriculture/Forestry Centre (AgFor), Agriculture/Forestry Centre, Edmonton AB
Event Details: 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 Rabaa Hamed. This seminar is open to the general public to attend.
Thesis Topic: Effects of Breed Type, Residual Feed Intake and Collagen Heat Solubility on Meat Quality, Connective Tissue Characteristics and Expression of Collagen-related Genes of m. Semimembranosus Muscle
Cattle breed, residual feed intake and genetics are factors that affect beef quality. Genotype can influence meat toughness and approximately 46% of beef quality variation can be attributed to the variation between animals. Calpain (CAPN1) and calpastatin (CAST) genes are associated with myofibrillar protein degradation early post mortem and are correlated with variation in beef toughness but the relationships between genes controlling collagen synthesis and degradation and beef toughness have not yet been examined. The objectives of this research were to: (1) determine the effect of breed and residual feed intake on beef quality and collagen characteristics; and (2) determine how the expression of genes involved in collagen synthesis and degradation were related to meat quality and collagen characteristics of the semimembranosus, a muscle from the inside round. Seventy-one (71) carcasses were harvested from purebred Angus (n = 23) and Charolais (n = 24) and Angus crossbred (Kinsella composite, n = 24) steers of high (n = 35) and low (n = 36) residual feed intake status. The m. semimembranosus muscle (inside round) was removed from the right side of each carcass, and steaks from each muscle were aged for 3 and 13 days. Breed and residual feed intake did not affect meat quality and collagen characteristics however post mortem aging decreased Warner-Bratzler shear force and increased collagen heat solubility.
From the data set, twelve steers with low [10.66 + 2.99 (standard deviation, SD) %] and twelve with high [20.61 + 7.51 (SD)%] intramuscular collagen heat solubility at day 3 post mortem were selected within each breed. The expression of 14 candidate genes in the m. semimembranosus was evaluated using quantitative real time polymerase chain reaction (RT-qPCR) using gene specific primer pairs relative to 18s RNA expression. Breed type significantly (P<0.05) affected the mean ∆Ct expression of CTGF, FOXO1, P4HA1 and SMAD2. Collagen heat solubility did not affect the expression level of the genes; however, there was an interaction between breed type and collagen heat solubility in the ∆Ct mean for CTGF expression. Sarcomere length was negatively correlated (P<0.001) with COL3A1 and COL5A2 and P4HA1 (P<0.05) gene expression. Warner-Bratzler shear force at 3 days post-mortem was negative correlated with COL3A1 (P<0.05) and FOXO1 (P<0.01) but was positively correlated with CTGF, IGF-1 while SMAD2. COL5A2 and MMP22 were positively correlated (P<0.05) with heat-soluble collagen at 3 days post-mortem. The concentration of pyridinoline cross links (mol PYR/mol collagen) was negatively correlated (P<0.05) with COL3A1 and COL5A2 while positively correlated with COL5A1. Expression of LOX was positively correlated (P<0.01) with the concentration of pyridinoline (nmol PYR/ g raw meat). Results indicated that expression of genes related to collagen synthesis and degradation were related to increased beef toughness. Overall, this study indicated that selection for low RFI cattle will not compromise m. semimembranosus meat quality, and that the contribution of collagen to beef toughness can be influenced through breed type selection.