Three groups of growing Sharabi calves were used in this study to evaluate the best suitable level of concentrate ration. Each group consisted of four calves between 8-12 months of age, with an average live body weight around 145 kg. They were fed for 90 days on concentrated standard ration according to NRC, 1984, at three different levels of 2, 3, 4 % of live body weight, respectively, consisted of 80:20 concentrate to roughage contained 14% crude protein, 72% TDN and 2.4 Mkcal/kg. ME. The total gain and amount of consumed ration were measured. At the end of the trial, samples of rumen fluid were collected from all calves in order to estimate the activity of bacteria and micro organism. Results showed that the average amount of the daily ration consumed by the three groups of calves were 3.68, 6.91 and 8.12 kg/calves, respectively. There were significant differences (P<0.05) in average daily gain among the three groups of calves (311, 869 and 1000 gm, for the three respective treatments). Also the feed conversion ratio was improved for the second and third groups compared with the first group and they were 7.96, 8.12 and 11.8 kg. ration/kg live body weight gain, respectively. Ration levels showed no effect on rumen fluid pH but increased the time of methylene blue reduction (more than 15 mints) and sedimentation activity test (more than 20 minuets) than their normal standard levels. The cost to produce one kg live body weight gain was about the same for the second and third groups and it was 50% less than first group and they were 3184, 3248 and 4746 I.D., respectively. It was concluded that the fattening regime for growing Sharabi calves on concentrated ration given at 4% of live body weight for three months had more economic profit.