Cassava forage was cut about 40 cm above ground, on average 4 months since the previous cutting. Its composition was given by Meyreles, MacLeod and Preston (NAR 47/B, 5833). It was chopped to about 30 or 300 mm. Each was given as fresh forage at 3% of bodyweight to 2 groups of 3 zebu bulls, total 12 bulls, aged 18 months and of initial weight about 180 kg. All had minerals and free access to a molasses and urea mixture. After 120 days on those diets, rumen fluid was collected by stomach tube before and 3 h after feeding from 2 cattle of each group, 4 of each treatment. For the first 56 days growth rate was 110 g daily with coarse and 50 g for fine-cut forage, but it was 580 and 660 g daily for the last 64 days, when the cattle also looked better and their hair was in better condition. That may have been due to adaptation to the diets, but whether to molasses or to cassava was not clear. There was no significant difference between coarse and fine forage in growth or efficiency or in rumen fermentation pattern.