The effect of 3 different dietary protein (with a specific associated amino acid profile) concentrations on certain production parameters in growing ostriches were investigated. Measured parameters included feed intake, feed conversion ratio, and growth rate. Basic abattoir mass, postmortem measurements of the commercial cuts of meat were also done. The crude protein and amino acid requirements of ostrich chicks for the different production phases (pre-starter; 19.0% CP, starter; 15.5% CP, grower; 14.25% CP and finisher; 12.6% CP) were predicted by a newly developed mathematical growth and optimization model for ostriches (Gous and Brand, 2008; Aust. J. Exp. Agric. 48:1266-1269). Three basic diets per production phase were then formulated to be 20% lower and 20% above these predicted levels for lysine, sulfur-containing amino acids, threonine, tryptophan and arginine (named diets with a low, medium or high protein content). In the study 18 groups of birds, with 10 birds per group were used as experimental animals and were alotted to the different treatments according to live weight. The 3 dietary treatments were evaluated with 6 groups of birds per treatment. The 3 diets with the different levels of dietary protein (with a specific amino acid composition related to the dietary protein content) were fed to the ostriches during each of the 4 production phases from hatching up to slaughtering. Feed and water was available ad libitum. Results were analyzed by ANOVA with dietary protein level as main effect. Differences were determined to be statistically significant at P < 0.05. Significantly lower values with the low protein diet for the final live mass of birds at slaughter at 300 d of age (respectively 89.6, 98.8 and 102.2 kg), cold carcass mass (respectively 41.2, 45.1 and 45.1kg) and thigh weight as well as for most of the weighed muscles were found, while values for the medium and high protein diet did not differ. Both ADG (respectively 338, 361 and 377 g/bird/day) and feed intake (respectively 1.63, 1.67 and 1.76 kg/bird/day) for the low protein diet was significantly lower than that of the high protein diet with the medium diet intermediate. Results indicated that birds that consumed the diet with the medium protein performed optimal in most cases, except during the starter phase where the high protein diet outperformed the other 2 diets. This study showed that feeding diets with a higher protein and amino acid content than that predicted by the model was unable to increase performance levels of growing ostriches in most cases.