The effects of two diets, a control diet (commercial feed with 39% crude protein) and an experimental diet (prepared based on 42% soybean meal with 38% crude protein), on growth performance of western white shrimp (Litopenaeus vannamei) in six 0.4-ha-earthen ponds (three replications per treatment) with 25 per m² density, were investigated. There was no significant difference in final weight (mean final weights were 15.7±0.88 and 15.6±0.52 g for the experimental and control treatments, respectively) between the treatments during the 115 days rearing period. There were no difference in FCR: 1.80±0.08 and 1.76±0.06, protein efficiency: 1.46±0.01 and 1.45±0.05, SGR: 2.38±0.04 and 2.38±0.03, final production: 2853.58±64.14 and 2864.83±168.57 kg/ha and survival rate: 91±1.78, 92±2.41% between experimental and control treatments, respectively (p>0.05) but net protein utilization in experimental treatment (17.05±0.38 g) and in the control (11.80±0.26 g) revealed significant differences (p<0.05). It is concluded that the experimental feed with 42% soybean meal was more efficient than the commercial feed on some growth parameters of western white shrimp.