Abstract
A total of 110 items of forage sorghum were harvested at the dough stage, and the digestibility of their foliage was evaluated. The digestibility experiment was conducted using the nylon-bag method on three Japanese black cows fitted with rumen fistula. The digestible dry matter content showed variation between 60.8-87.4%. The lower values corresponded to the content in inferior grass hay (56.0-61.2%) or rice straw (56.8%) tested under the same conditions, while the higher values exceeded the content in corn silage (79.9%). In particular, brown midrib lines and varieties with high culm juice brix were highly digestible. The water-soluble matter content varied between 21.5-60.0% showing a significant positive correlation with the digestible dry matter content (r= +0.55). The digestible structural matter content varied between 19.2-57.0% and showed a significant negative correlation with the watersoluble matter content (r=-0.76). The digestibility characteristics of brown midrib lines were distinctly different from those in the normal varieties. It was attributable to the high digestible structural matter content in comparison to normal varieties (10-15%), rather than the high water-soluble matter content.
