Abstract
We investigated the effects of feeding whole-crop rice silage (rice-WCS), prewilted to reduce β-carotene content to about 2.8mg/kg DM, on feed intake, growth, blood components, and carcass traits in Japanese Black steers. This diet, fed during the fattening period, was substituted for hay and rice straw. Eighteen steers were divided into 3 groups: control (n=6), fed Italian ryegrass hay and rice straw during the early (8-13 months of age) and late (14-24) stages, respectively; WCS-rice straw (n=6), fed on rice-WCS and rice straw during the early and late stages, respectively; and rice-WCS (n=6), fed on rice-WCS during both stages. Daily dry matter intake was significantly higher in the rice-WCS group. Although insignificant, plasma retinol levels tended to be higher in the rice-WCS group than in other groups. Daily dry matter intake in the rice-WCS group was 1.58kg, and the plasma retinol level decreased to 50IU/dL at 19 months. Differences in daily weight gain (>0.8kg in all groups), carcass grade, and beef marbling scores were not significant among all 3 groups. The fat color score was estimated as 3 for each of the 18 carcass. Thus, rice-WCS with reduced ,β-carotene content is a recommended diet throughout the fattening period for Japanese Black steers.
