A study was conducted to determine the dietary effects of Na-bentonite (NaB) and probiotics on meat characteristics and health of Hanwoo steers fed rice straw as a sole roughage source. A total of 24 growing Hanwoo steers (avg BW 232 kg) were assigned to two treatments which included a control diet (concentrate mix and rice straw) and a treatment diet (control diet + 0.5-1.0% NaB + 0.5-1.0% probiotics. The diets were fed for 22 months up to the time the animals were slaughtered. Dietary treatment increased (p<0.05) concentrations of trace minerals such as Zn, Cu, and Fe in the longissimus muscle compared to the control. The treatment diet did not affect cold carcass weight, yield traits such as backfat thickness, longissimus muscle area, yield index, yield grade and quality traits such as marbling score, meat color, fat color, texture, maturity and quality grade. Blood profiles of growing steers were within the normal ranges for healthy cattle. In conclusion, feeding a combination of clay mineral and probiotics to Hanwoo steers fed rice straw as a sole roughage source could have a desirable effect on improving trace mineral retention in longissimus muscle without any deleterious effects on carcass traits of steers.

• Wan-Sup Kwak(Animal Science, School of Life Resource and Environmental Sciences College of Natural Sciences, Konkuk University) Corresponding author
• Sang-Moo Lee(Department of Animal Science, Kyungpook National University)
• Young-Il Kim(Animal Science, School of Life Resource and Environmental Sciences College of Natural Sciences, Konkuk University)