In a study over two breeding seasons, we assessed the effect of dietary energy and protein levels on body mass, body condition and the production of fertile eggs by male ostriches. During the first season, birds were fed diets with energy levels of 8.5, 9.5 or 10.5 MJ/kg dry mass (DM) metabolisable energy (ME), and 13.5, 15 or 16.5% protein. Corresponding lysine levels were 0.65, 0.75 and 0.85%. In the second breeding season, the groups were fed diets with energy levels of 7.5, 8.5 and 9.5 MJ/kg ME and protein levels of 10.5, 12 and 13.5%. Corresponding lysine levels were 0.49, 0.59 and 0.69%. During the first breeding season, the mass of all birds increased, but the mass of those fed the 8.5 MJ/kg ME diet was significantly lower at the end of the season than that of birds fed diets of 9.5 and 10.5 MJ/kg ME. During the second season, the trend in the case of the 8.5 and 9.5 MJ/kg diets was the same as in the previous season, but a significant decrease in mass occurred in birds fed the 7.5 MJ/kg diet. A general loss of body condition occurred for all energy levels. In contrast to energy levels, different protein levels in the diets had no significant effect on any parameters measured. There were no trends or significant differences in the production of fertile eggs with any of the experimental diets. We conclude from this study that a level of 8.5 MJ/kg DM ME and 10.5% protein in the diet of breeding male ostriches is sufficient if maintenance in mass is the main criteria for adjusting rations.