A nine weeks growth study was carried out to investigate, how the dietary supplementation of essential amino acids (EAA) could help in the reduction of intact protein (IP) level in diets designed for juvenile (10.6g) channel catfish Ictalurus punctatus. The effect on fish growth, feed utilization, proximate composition, and serum indicators was measured. Five iso-lipid containing (8%) lipid experimental diets were formulated with graded levels of intact protein (32, 30, 28, 26 and 24 %IP) supplemented with EAA (lysine and histidine)to maintain the in EAA level as recommended in NRC 2011. The results of fish growth; final mean weight (g), weight gain, weight gain percent, feed conversion ratio (FCR), feed intake (g) of channel catfish were not significantly different as IP was decreased from 32 to 26 %, with EAA supplementation. Fish growth was significantly reduced, while FCR significantly increased as IP was lowered to 24%. The reduction of IP in-channel catfish diet with EAA supplementation did not affect whole-body crude protein, moisture, ash, crude fiber, and amino acid contents. While whole-body fat significantly increased with lowering of the IP content in the diet. Serum total protein, albumin, total immunoglobulin, and glucose level were not significantly affected by the reduction of the dietary IP level for 32 to 24%. While, serum ALT, AST, ALP and triglycerides levels showed a significant increase, while serum lysozyme and total hemoglobin decreased as protein was decreased to 24%. In conclusion, commercial amino acids could be used as a dietary supplement to reduce intact protein content from 32 to 26% in channel catfish diets with maintaining a comparable fish growth and health. But, fish growth, body composition, and serum metabolites were adversely affected by further lowering of protein to 24%.
Keywords: Channel catfish, Essential amino acids, intact protein, commercial amino acids.