Investigation of blood biomarkers related to meat quality and quantity in Hanwoo steers

Objective: This study was conducted to investigate the correlation between blood components and carcass traits, and to find the biomarkers related to meat quality and quantity in Hanwoo steers. Methods: One hundred twenty-six Hanwoo steers (8 to 9 months of age, body weight of $185.6{\pm}24.38kg$) were used to find the correlation between blood compositions and carcass traits. The steers were fed concentrate and rice straw (30 steers) or total mixed rations (96 steers) during the whole experimental period. Blood samples were collected from the jugular vein at the growing (8 to 12 months), fattening (13 to 23 months) and finishing phases (24 to 30 months). Steers were slaughtered at 30 to 31 months of age (body weight of $701.6{\pm}60.45kg$) and the carcass traits were evaluated. Blood metabolites and hormones were analyzed and the correlation coefficients and regression equations with carcass traits were determined. Results: Average concentrations of retinol, leptin and insulin were 1.10 IU, 30.34 ng, and 35.35 ng per mL of blood plasma, respectively. Retinol has negative correlations (p<0.01) with insulin and leptin. Blood insulin and total protein decreased with the age of steers, but retinol, aspartic acid transaminase (AST), glucose, cholesterol and triglyceride increased. In the finishing phase, significant (p<0.01) negative correlations occurred between blood retinol content and marbling score, and between blood AST content and longissimus muscle area of 13th rib, and the following regression equations were obtained: Marbling score $(1-9)=-0.009{\times}retinol(IU/100mL)+9.125$ ($R^2=0.643$), Longissimus muscle area $(cm^2)=-0.250{\times}AST(U/L)+112.498$ ($R^2=0.450$). Conclusion: It is possible to make highly marbled beef by controlling the blood retinol content during the fattening and finishing phases of Hanwoo steers. Accordingly, blood retinol and AST could be biomarkers for determining beef quality and quantity, respectively, prior to slaughter.