Relationships among carcass traits, auction price, and image analysis traits of marbling characteristics in Korean cattle beef

- Invited Review - Factors affecting beef quality and nutrigenomics of intramuscular adipose tissue deposition

Beef quality is characterized by marbling (marbling degree and marbling fineness), physiochemical (shear force, meat color, fat color, texture, and maturity), and sensory (tenderness, flavor, juiciness, taste, odor, and appearance) traits. This paper summarizes and addresses beef-quality characteristics and the beef-grading systems in Korea, Japan, the USA, and Australia. This paper summarizes recent research progresses on the genetic and nutritional factors that affect beef quality. Intramuscular (i.m.) adipose tissue deposition or marbling is a major determinant of beef quality. This paper addresses the mechanisms of i.m. adipose tissue deposition focused on adipogenesis and lipogenesis. We also address selected signaling pathways associated with i.m. adipose tissue deposition. Nutrients contribute to the cellular response and phenotypes through gene expression and metabolism. This paper addresses control of gene expression through several nutrients (carbohydrates, fat/fatty acids, vitamins, etc.) for i.m. adipose tissue deposition. Several transcription factors responsible for gene expression via nutrients are addressed. We introduce the concept of genome-based precision feeding in Korean cattle.

Main regulatory factors of marbling level in beef cattle

The content of intramuscular fat (IMF), that determines marbling levels is considered as one of the vital factors influencing beef sensory quality including tenderness, juiciness, flavour and colour. The IMF formation in cattle commences around six months after conception, and continuously grows throughout the life of the animal. The accumulation of marbling is remarkably affected by genetic, sexual, nutritional and management factors. In this review, the adipogenesis and lipogenesis process regulated by various factors and genes during fetal and growing stages is briefly presented. We also discuss the findings of recent studies on the effects of breed, gene, heritability and gender on the marbling accumulation. Various research reported that feeding during pregnancy, concentrate to roughage ratios and the supplementation or restriction of vitamin A, C, and D are crucial nutritional factors affecting the formation and development of IMF. Castration and early weaning combined with high energy feeding are effective management strategies for improving the accumulation of IMF. Furthermore, age and weight at slaughter are also reviewed because they have significant effects on marbling levels. The combination of several factors could positively affect the improvement of the IMF deposition. Therefore, advanced strategies that simultaneously apply genetic, sexual, nutritional and management factors to achieve desired IMF content without detrimental impacts on feed efficiency in high-marbling beef production are essential.

Comparison of transcriptome between high- and low-marbling fineness in longissimus thoracis muscle of Korean cattle

Objective

This study compared differentially expressed genes (DEGs) between groups with high and low numbers of fine marbling particles (NFMP) in the longissimus thoracis muscle (LT) of Korean cattle to understand the molecular events associated with fine marbling particle formation.

Methods

The size and distribution of marbling particles in the LT were assessed with a computer image analysis method. Based on the NFMP, 10 LT samples were selected and assigned to either high- (n = 5) or low- (n = 5) NFMP groups. Using RNA sequencing, LT transcriptomic profiles were compared between the high- and low-NFMP groups. DEGs were selected at p<0.05 and |fold change| >2 and subjected to functional annotation.

Results

In total, 328 DEGs were identified, with 207 up-regulated and 121 down-regulated genes in the high-NFMP group. Pathway analysis of these DEGs revealed five significant (p<0.05) Kyoto encyclopedia of genes and genomes pathways; the significant terms included endocytosis (p = 0.023), protein processing in endoplasmic reticulum (p = 0.019), and adipocytokine signaling pathway (p = 0.024), which are thought to regulate adipocyte hypertrophy and hyperplasia. The expression of sirtuin4 (p<0.001) and insulin receptor substrate 2 (p = 0.043), which are associated with glucose uptake and adipocyte differentiation, was higher in the high-NFMP group than in the low-NFMP group.

Conclusion

Transcriptome differences between the high- and low-NFMP groups suggest that pathways regulating adipocyte hyperplasia and hypertrophy are involved in the marbling fineness of the LT.