Source: Ontario Ministry of Agriculture, Food and Rural Affairs
Meat quality traits such as meat colour and marbling are important because of their strong impact on consumer acceptance as visual indicators of meat freshness and juiciness. Consumers assess beef quality through physical aspects, including visual appearance. Studies indicate that consumers are willing to pay more for beef cuts that are bright red in colour and that presents different patterns of fat content, matching the individual requirements of each type of consumer. Thus, marbling and meat colour are important traits to consider in a breeding program.
Some studies have characterized the biochemical patterns of beef colour to explain the multitude of biochemical interactions during the aging process, which impacts the final appearance of beef. A study by Gagaoua et al. (2017) investigated the meat colour trait in the rib eye steak of young Aberdeen Angus and Limousin bulls. These authors suggested the possibility of using biomarkers, or biological indicators, that can be used to classify meat cuts sampled at early post-mortem according to colour.
Marbling refers to the extent of fat that is deposited intramuscularly, or inside the muscle tissue, and can affect other meat quality traits such as colour and tenderness. According to Jung et al. (2016), the correlation between marbling and juiciness is around 0.67, which is moderately high. This means that by improving marbling, we can often increase the sensory flavour and juiciness. Additionally, increased marbling can compensate for the effects of increased cooking temperatures on less tender muscle. Furthermore, increased marbling has the potential to yield more beneficial fatty acids (i.e. omega 3), which has been identified as an important factor for more nutritious and healthier food (Cánovas et al., 2012).
Despite the importance of these traits, genetic and physiological understanding of beef colour and marbling is growing slowly and still little is known about the genes determining these traits and their functions. This represents a significant unexplained source of variation of phenotypes remaining in beef cattle. While there are challenges in reducing this variation, there is potential to identify genetic markers that are associated with marbling and colour in beef cattle along with a precise understanding of the biology underlying these traits. This will allow for a more effective improvement in meat quality through genetic selection and feeding management. Thus, functional genomics studies using the new – OMICS technologies such as transcriptomics could help to clarify the genetic architecture of these traits, ultimately to enhance the reliability and accuracy of selection methods for beef quality traits.
In this sense, one of the research lines in the Cánovas Lab at the Univeristy of Guelph have been studying the muscle transcriptome profile associated with meat quality using high throughput -OMICS technologies such as transcriptomics with RNA-Sequencing. This new technology aims to identify the specific gene forms (mRNA isoforms) that are been expressed in the muscle of animals with higher marbling compared to animals that have less marbling. In addition, the research team is digging even deeper to identify the biological markers responsible for the different patterns of genetic expression presented by animals that result in different marbling profiles.
One of those projects was conducted in collaboration with UNESP in Brazil (Albuquerque Lab), and the preliminary results are promising. So far the study has identified genes, such as hemoglobin, that have showed different patterns of expression between Nellore cattle with bright red meat and greater marbling compared to animals with dark coloured meat with reduced marbling. The hemoglobin gene produces an important protein responsible for determining meat colour.
The collagen gene has shown different patterns of expression between animals with high and low levels of beef marbling and tenderness (Muniz et al., 2020). This study identified structural variants (markers) possibly responsible for modifying the collagen protein in animals with different levels of marbling. These preliminary results have shown that the genetic mechanisms that possibly control meat colour and the levels of marbling could be connected each other. Th next steps of this research includes validation of these results in beef breeds used for the Canadian meat production system.
Cánovas A, Pena RN, Gallardo D, Ramírez O, Amills M, Quintanilla R (2012) Segregation of regulatory polymorphisms with effects on the gluteus medius transcriptome in a purebred pig population. PloS one 7 (4), e35583
Gagaoua M, Terlouw EMC, Picard B (2017) The study of protein biomarkers to unders tand the biochemical processes underlying beef color development in young bulls. Meat Sci. 134:18-27. doi: 10.1016/j.meatsci.2017.07.014.
Gordo DGM, Espigolan R, Tonussi RL, Júnior GAF, Bresolin T, Braga-Magalhães AF, Feitosa FL, Baldi F, Carvalheiro R, Tonhati H, de Oliveira HN, Chardulo LAL, de Albuquerque LG (2016) Genetic Parameter Estimates for Carcass Traits and Visual Scores Including or Not Genomic Information. J Anim Sci 94(5):1821-6. doi: 10.2527/jas.2015-0134.
Muniz MMM, Fonseca LFS, Magalhães AFB, Silva DBS, Cánovas A, Lam S, Ferro JA, Baldi F, Chardulo LAL, Albuberque LG (2020) Use of gene expression profile to identify potentially relevant transcripts to myofibrillar fragmentation index trait. Functional and Integrative Genomics 20(1). Doi: 10.1007/s10142-020-00738-9.
Jung EY, Hwang Y H, Joo ST. (2016) the Relationship between Chemical Compositions, Meat Quality, and Palatability of the 10 Primal Cuts from Hanwoo Steer. Korean J Food Sci Anim Resour. 36(2):145-51. doi: 10.5851/kosfa.2016.36.2.145.
|M.M. M. Muniz, Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, ON
L. F. S. Fonseca, São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP
F. Baldi, São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP
A. Cánovas, Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, ON
L.G de Albuquerque, São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences, Jaboticabal, SP