This study was conducted to investigate the effects by supplementing concentrates during the late fattening phase in TMR (total mixed ration) feeding of Korean steer on the performance, carcass traits, physico-chemical characteristics and sensory test of the longissimus dorsi muscle. Eight Korean steers (24 months of age) averaging 604 kg in body weight were fed the TMR (Control) or the TMR supplemented with concentrates (TMR+conc.) until 30 months of age, then they were slaughtered. Steers fed the TMR supplemented with concentrates had a higher (p<0.05) intakes of dry matter and TDN (total digestible nutrient), carcass weight and marbling score compared to those fed TMR only, but carcass grade did not differ (p>0.05) between treatments. Amino acid concentration of the longissimus dorsi muscle did not differ between treatments, However, the highest concentrations were for glutamic acid and lowest for cystine; further, and the content of essential amino acids was highest for lysine, leucine, threonine, arginine, and isoleucine in that order. Cis-oleic acid and arachidonic acid of fatty acids in the longissimus dorsi muscle were higher (p<0.05) in the control condition compared to TMR+conc. The contents of oleic acids, palmitic acid, stearic acid constituted about 88% of the total fatty acids. Although the physico-chemical characteristics of the longissimus dorsi muscle did not significantly differ between treatments (p>0.05), but the sensory test results were lower for the TMR+conc. condition. These results suggest that supplementing concentrates during the late fattening phase of Korean steers resulted in increasing the carcass weight and marbling score. However, the cis-oleic acid content of the longissimus dorsi muscle was decreased as a result of supplementing concentrates, which could affect negatively in meat sensory evaluation.

The current study was conducted to investigate effects of sera taken from Hanwoo at different age on adipocyte differentiation. Sera were taken from Korean native (Hanwoo) steers at 6, 12, 18, and 24 months of age, respectively and supplemented to 3T3-L1 preadipocytes after the cells reached confluence and maintained 10 days thereafter. For the first 2 days (48 h), cells were induced to differentiate by addition of differentiation factors, methylisobutylxanthine, daxamethasone, and insulin. After the differentiation, the cells were incubated without differentiation factors except insulin. The cells lost their fibroblastic shape and showed round-up appearances after 10 days incubation with FBS and the sera of Hanwoo steers. Big lipid droplets appeared in the cells cultured with FBS and the sera taken from Hanwoo at 18 and 24 months of age. After 18 months of age, GPDH activity was statistically higher than 6 and/or 12 months of age (P < 0.05). Based on morphology and Sn-glycerol-3-phosphate dehydrogenase activities, Hanwoo steers expressed aged-dependent adipogenic activities, indicating that aged sera may result in high adipocyte differentiation. It is concluded that the 18 months of age may be ‘threshold’ to express major adipogenic activities. This may strongly support previous field studies reporting considerable increase in fat contents of Hanwoo carcass at over 18 months of age.