Effects of dietary pyridoxine and protein levels on growth, vitamin B 6 content, and free amino acid profile of juvenile Penaeus japonicus

Abstract

A 2 × 2 factorial design was utilized to evaluate the effects of dietary pyridoxine (0 and 200 mg kg −1 diet) and protein (49 and 64%) levels on growth, B 6 vitamer content, and free amino acid profile of juvenile Penaeus japonicus (0.17 ± 0.03 g; mean ± sd) after a 10-week feeding experiment. Pyridoxine (PN) and protein levels significantly ( P < 0.05) improved weight gain, feed intake, feed efficiency, and increased whole body protein content, muscle glutamate oxaloacetate transaminase activity, and ammonia-N excretion. Interaction between these two factors was not significant ( P > 0.05) for those mentioned variables. Weight gain of prawns fed the PN-supplemented diets was almost 2 × higher than that of prawns fed diets without supplemental PN. Significant increases in body protein, protein efficiency ratio, protein retention, and weight gain indicated that dietary protein was efficiently deposited in the body of prawns fed PN-supplemented diets. Pyridoxal phosphate and pyridoxamine phosphate were the predominant forms of vitamin B 6 in both the hepatopancreas and muscle, and their levels were significantly higher in prawns fed PN-supplemented diets. Higher levels of aspartic acid, threonine, serine, glycine, valine, and tyrosine were found in whole body of prawns fed diets without supplemental PN suggesting that catabolism of these amino acids was reduced in the prawns deficient in vitamin B 6, thereby resulting in reduced ammonia-N excretion.