Urinary amino acid excretion by marine shrimp, Penaeus monodon, in response to orally administrated intact protein and crystalline amino acids

Oral protein administration was conducted to gain more insight into the ability of the shrimp (Penaeus monodon) to utilize different protein sources and estimate the urinary amino acid excretion. Both intact protein diet and a corresponding crystalline amino acid diet were administrated orally after the cannulated shrimp were fasted for 24 h. Urine was then collected from the shrimp for 24 h. Each treatment had five replicates. Free amino acid concentrations in urine of shrimp fed the crystalline amino acid diet were significantly higher than those of shrimp fed the intact protein diet. The total amino acids lost in urine was about 6% of the total oral crystalline amino acids in the diet. The individual amino acids lost in urine as a percentage of the crystalline amino acids in the diet were 13.6% for His, 17.6% for Phe, and about 8-10% for Ile, Leu, Lys and Val, respectively. In addition to the high concentration of free amino acids in the plasma which might induce catabolism of the absorbed dietary amino acids, the high percentage of amino acids lost in the urine could be another explanation of poor utilization of crystalline amino acids by shrimp.