Effects of long-term starvation on body weight and body composition of juvenile channel catfish, Ictalurus punctatus, with special emphasis on amino acid and fatty acid changes

Triplicate groups of 30 channel catfish Ictalurus punctatus (initial weight: 76.13 ± 0.78 g) were stocked in indoor flow-through fiberglass tanks and starved for 80 days. Body weight, morphometric parameters, body composition, amino acid and fatty acid changes in muscle and liver tissues were investigated to determine the effect of long-term starvation on body weight and body composition of juvenile channel catfish. During the starvation period, body weight, condition factor (CF), viscerosomatic index (VSI), hepatosomatic index (HSI) and intraperitoneal fat ratio (IPR) declined (P < 0.05). In the whole body, both protein and lipid decreased while changes in the amount of fat were relatively rapid. Hepatic lipid and carbohydrate contents declined as starvation progressed, but crude protein and moisture contents increased (P < 0.05). In contrast, muscle crude protein showed a greater decline than did muscle lipids, and muscle glycogen remained relatively constant. During the 80-day starvation period the ratio of total essential amino acids (EAA) to total non-essential amino acids (NEAA) in muscle and liver (P < 0.05) increased. In muscle tissue, total mono-unsaturated fatty acids (MUFA) and n-6 fatty acids decreased, but total saturated fatty acids (SFA) and n-3 fatty acids, as well as the ratio of n-3 to n-6 fatty acids increased (P < 0.05). However, in the liver, starvation resulted in the relative increase of total MUFA and reduction in n-3 fatty acid contents as well as the ratio of n-3 to n-6 fatty acids (P < 0.05). Based on these observations, lipids and glycogen can be considered as more important sources of catabolizable energy in liver, whereas protein might be preferentially mobilized in muscle; lipids played a more important role as energy reserves on a relative basis in the whole body. Channel catfish preferentially utilized NEAA to EAA as an energy substrate and preferentially reserved EAA during starvation. Mobilization of fatty acids showed more variation in the muscle and liver during starvation.