2.1. Animals and sampling
Six JB and 6 HS steers were kept under the same conditions from 10 to 26 months of age. The animals were cared for and slaughtered according to Guidelines for Animal Experiments in the Faculty of Agriculture of Kyushu University and to laws of the Japanese Government (Law No. 105, Notification No. 6). Steers were raised in a pen with group feeding using the standard feeding system for the production of marbled beef (Gotoh et al., 2009). They were fed twice daily a high energy diet starting at 10 months of age until slaughter at 26 months of age. From 10 to 18 months of age, the diet consisted of increasing amounts of concentrate (36.8 to 86.4%, formula feed) and respectively decreasing amounts of roughage (jamboree, hay and rice straw). During the last stage from 18 to 26 months of age, the diet consisted of 86.4 to 84.2% of concentrate and 13.6 to 15.8% roughage. All steers had permanent access to water and to mineral salt blocks (Cowstone A, Nippon Zenyaku Kogyo, Japan) that contained minerals, salt, and a diuretic. Consumed feed of the groups was recorded daily.