Effects of aspartic and/or glutamic acid addition to diet with low protein and soybean-based meal on growth performance of tilapia (Oreochromis niloticus)

This study was carried out in two experiments to investigate the effects of two dietary attractants in diets containing two protein levels and protein sources on growth performance and feed consumption of tilapia (Oreochromis niloticus) fingerlings under aquarium conditions.In the 1st experiment, the average weight of 2 g of fish were fed for 80 days on diets including two protein levels (24 and 32%) and three levels (0.5, 1 and 1.5%) of either aspartic acid or glutamic acid added into each respective diets. At the end of the trial, 24% protein feed containing 1% addition of glutamic acid and/or aspartic acid provided similar growth and feed conversion ratio to that of the diet containing 32% protein (P>0.05). Using of combination of glutamic acid and aspartic acid did not show a synergy effect.In the 2ndexperiment, the fish averaging 7g were fed for 60 days on diets containing two protein sources (40% fish meal and 40% soybean meal) supplemented with either 1% aspartic acid or 1% glutamic acid. At the end of the trial, the diet including 40% soybean meal and 1% glutamic acid and/or aspartic acid promoted similar growth and feed conversion ratio to the diets containing fish meal as protein source (P>0.05). Using of combination of glutamic acid and aspartic acid did not show a synergy effect.As a result, in order to reduce feed costs, when the fish are reared at low-protein diets including soybean meal as protein source, the fish growth and feed consumption can be improved by the addition of 1% glutamic acid as attractant into such diets.