An experiment was conducted with 72 male British Friesian calves between 5 and 11 weeks of age. The major treatments were the inclusion of 0, 20 or 40% wheat straw or 20, 40 or 60% lucerne in a complete pelleted diet. The roughage was either ground or chaffed. A methane inhibitor was included in the diets given to 36 of the calves. The weight gains of the calves were greater with diets containing lucerne than with those containing wheat straw. Grinding increased the intake of wheat straw but depressed intake of lucerne. The apparent digestibility of dry matter and acid detergent fibre, which was greater for the diets containing lucerne than for the diets containing wheat straw, was reduced by grinding both roughages.
Inclusion of the methane inhibitor in the diets increased the feed intakes and weight gains of the calves given the all-concentrate diet and the diets containing wheat straw, but not those given the diets containing lucerne.