Plasma Amino Acid Changes in Rainbow Trout Salmo gairdneri Force-fed Casein and a Corresponding Amino Acid Mixture

Abstract

The sequence of appearance of free amino acids in the plasma of rainbow trout at 0, 3, 6, 12, 24, 36, 48, 72, and 96 hours after force-feeding casein and a corresponding amino acid mixture was examined. Most of the free essential amino acids in the plasma of rainbow trout after force-feeding casein did not appreciably change from their fasting levels during the initial 12 hours, but thereafter increased in concentration to attain maximum levels between 24 and 36 hours after force-feeding, and then declined to the fasting levels after 72 to 96 hours. In contrast, most of the plasma free essential amino acids increased immediately after force-feeding the amino acid mixture and reached mean peak levels at 12 hours, returning to their fasting levels by 48 hours Compared with the fish which were force-fed casein, those force-fed the amino acid mixture showed higher essential amino acid concentrations in plasma at their maximum levels. Also, examination of the stomach contents of the fish at these same intervals after force-feeding revealed the amino acid mixture to be emptied from the stomach more rapidly than the casein. © 1981, The Japanese Society of Fisheries Science. All rights reserved.