Evaluation on the use of free amino acids in diets for red tilapia fries

Abstract

An experimental investigation was conducted to address the question of the optimum proportion of protein, free amino acid mixture and test how red tilapia fries will respond to casein-gelatin based diets with partial and/or total replacement with FAA mixture. The protein used was the mixture of casein-gelatin (5:1) and free amino acids matched the casein-gelatin profile. Eight experimental diets based on the use of casein and gelatin (CG)-based diets were analyzed, and five feeding treatments with incomplete replacing of dietary protein with a mixture of FAA with uncertain AA profile. The casein and gelatin were replaced at different levels of 10% (FAA10), 20% (FAA20), 30% (FAA30), 40% (FAA40), and 50% (FAA50) and another two control diets without FAA inclusion. Red tilapia, Oreochromis mossambicus × O. niloticus fries with initial average weight of (0.13 g ±0.01) were fed for an 8-week feeding trial. The results of this study showed that fish fed CG diet had a significant effect (P<0.05) of higher mean final body weight (2.29 g) and specific growth (5.1% /day) than on the Cont 1 diet. During prolonged double feeding, the FAA30 treatment group presented the highest (worst) FCR (1.20) and was significantly different from the cont1 group (P<0.05) gives the lowest (best) value (0.89). The survival rate of the fish fed the experimental diets did not differ significantly with an average of 95.4% (P >0.05).There was no significant difference (P>0.05) in dry matter and ash contents of red tilapia fed with the examined diets. Fish fed the FAA50 and FAA30 diets had the highest lipid content (P<0.05), unlike the other treatments. There was a significant difference in the whole body of red tilapia fed the FAA40 diet (P<0.05), and has a high level of all amino acids compared to FAA30 diet and mostly higher than other groups. Despite the presence of beneficial nutrients such as casein and gelatin mixture, it can be concluded that the FAA components in red tilapia diets can increase growth and feed efficiency.