Four studies were conducted with the solid precipitate of aerobically sustained swine waste. Settled solids (ODR) collected from an oxidation ditch and containing 27.7% protein were substituted for other protein sources in studies with weanling rats. The protein of ODR could replace one-third to one-half of the protein of casein or soybean meal and support similar weight gains although gain/feed ratio decreased as ODR was increased in the diet. Feed intake was not reduced by the addition of ODR in any of the studies. The protein and energy digestibility values for ODR were less than those for the casein containing basal diet. The addition of lysine or tryptophan individually to a corn-ODR diet did not influence gain while the combination significantly increased gain and gain/feed suggesting that these amino acids were most limiting and nearly equally limiting in that diet.