In experiments with adult Merino wethers, where wheaten straw was supplemented with an urea-containing mixture, the following was found: (a) Poor quality roughage may maintain the body weight of Merino sheep provided that the organic matter digestibility is not lower than 45% (b) An organic matter digestibility level of 45 % can be attained by supplementing low quality roughages similar to wheaten straw with urea-containing licks. (c) A maintenance ration consisting mainly of low quality roughage can maintain live weight, but will not increase it due to the close relationship that exists between voluntary feed intake and metabolic body size. (d) Digestion ,stimulatorv licks should be made available to ruminants from the stage when the nutritional value of pastures begins to decrease and the animals are still in a good condition. This will ensure that the summer condition of the animals is maintained to a greater degree as a result of a timely prevention of a sudden decrease in the intake and digestibility of roughage. The better condition of the animals will, in turn, ensure a greater feed intake as a result of the relationships between the latter factor and the metabolic body size of the animal.