The feeding value of oil palm by-product composed of palm press fiber, palm kernel cake and palm oil sludge was studied by determining the digestibility, nutrient intake and physiological responses to three different feeding treatments, using three fistulated Kedah-Kelantan cattle.
　In the treatment 1, oil palm by-product ration and rice straw with molasses was used. In the treatment 2, oil palm by-product ration alone was used, and in the treatment 3 napiergrass replaced a part of oil palm by-product ration. The amount of rice straw or grass offered was planned to replace 30% of the total dry matter intake. The results are as follows:
　1) The three feeding treatments tested in this study can be applied to Kedah-Kelantan cattle without a risk of heat stress as far as they are fed under shade. Further study must be made for calf, lactating cows and cattle not under shade from the standpoint of feeding and environmental physiology.
　2) Intake of total digestible nutrients observed in all the treatments exceeded the requirement for steer of 250 kg, gaining 250 g/day, but digestible crude protein intake was higher than the requirement only in the treatment 2. The oil palm by-product ration meets the total digestible nutrients, digestible crude protein and crude fiber contents of rations for dairy cattle recommended by NRC.
　3) Napiergrass feeding seemed to stimulate the intake of oil palm by-product ration but the result suggested that the upper limit of replacement should be 25% of total dry matter of the ration. The upper limit of rice straw also should be 25%.
　4) The oil palm by-product ration is a good ration for the cattle weighing approximately 250 kg. But it is required to increase the nutrient content for applying it to the cattle of bigger size or lactating cows, i.e. the cattle of higher nutrient requirements.