In pen feeding trials with eight Merino wethers, digestion coefficients were estimated for rations of cereal chaff-wheat grain-oat grain mixture, and wheat grain and oat grain fed separately at two levels of intake. Digestion coefficients for wheat and oat grain fed at 675 g/day in a double crossover experiment were dry matter 89.4, 80.8 per cent, organic matter 90.1, 82.6 per cent, protein 82.3, 77.6 per cent, ether extract 84.1, 90.9 per cent, crude fibre 33.2, 59.9 per cent, nitrogen free extractives 93.2, 85.8 per cent, energy 88.1, 81.0 per cent, total digestible nutrients 91.6, 87.1 per cent, and starch equivalents 90.7, 85.7. When these grains were fed at 785 g/day there was about 10 per cent improvement in crude fibre digestibility for both grains and 1-2 per cent improvement for other estimations with oats but not with wheat. The gross energy content of the wheat and oat grains when fed at 675 g/day was 4407 and 4700 calories/g dry matter. The digestible energy of the wheat in calories/g dry matter and organic matter was 3869 � 30, 3933 � 30 and for oats 3791 � 59, 3910 � 61. When fed at 785 g/day these values for wheat were 3850 � 50,3911 � 51 and for oats 3796 � 34, 3913 � 51. A highly significant relationship was found between energy and dry matter digestibility which for wheat diets was Y = 1.074x 7.840. r = 0.993 (P<0.001), and for oats and the mixed diet of cereal chaff-oat grain-wheat grain, Y = 0.983x + 1.550. r = 0.996 (P<0.001) where Y = energy and X = dry matter digestibility and r = the coefficient of correlation. Because of the similar digestible energy content of, and the body weight gains of sheep on, these two grains it was concluded that under the present conditions these grains were equivalent weight for weight.
