Kyu-Il Kim

Requirements for lysine and arginine by rainbow trout (Oncorhynchus mykiss)

A series of experiments was conducted to determine lysine and arginine requirements of fingerling rainbow trout. Four groups of 30 trout each were assigned per diet and fed three times daily to satiation at 15 °C. The diets contained varying levels of lysine and arginine. Weight gain of 13.7-g trout over a 6-week feeding period increased linearly with lysine level up to 1.4% of diet, but was not different at 1.4 and 1.6% lysine. Feed efficiency and nitrogen retention improved as the lysine level in the diet increased. Carcass protein content of trout fed diets containing sufficient ivsine was higher than that of trout fed diets deficient in lysine. No significant differences in weight gain were shown between 11.6-g trout fed diets containing 0.47% arginine and either 1.5 or 3.0% lysine, indicating no apparent interactions between the dietary arginine and lysine levels. Weight gain of 12.4-g trout over a 6-week feeding period significantly (P < 0.05) increased with dietary arginine level up to 1.3%, but further increases in the arginine level did not have a significant effect. A similar trend was noted in feed efficiency, nitrogen retention and carcass protein content. Analysis of weight gain versus dietary lysine or arginine level indicated that the lysine and arginine requirements of young trout are 1.30 (3.71) and 1.41 (4.03)% of diet (protein), respectively.

Purified diet development and re-evaluation of the dietary protein requirement of fingerling rainbow trout (Oncorhynchus mykiss)

Abstract Two experiments were carried out to develop a purified diet, and to examine the protein requirement of fingerling rainbow trout. Four replicate tanks (50 fish each) of trout were assigned to a commercial salmon diet or a purified diet containing 30, 35, 40 or 45% protein; and three replicate tanks (40 fish each) to a diet containing 10, 15, 20, 25 or 35% protein (not counting crystalline dispensable amino acids which replaced casein protein to vary the protein level). Trout were fed three times a day for 6 weeks, and weight gain and feed gain ratio were monitored No significant differences were found in weight gain or feed gain ratio among 10.5-g fish fed diets containing 30, 35, 40 and 45% protein. Fish fed these diets gained about 80% as much weight as fish fed a commercial salmon diet which produced gain of 19.5 g/fish per 6 weeks. Weight gain increased with the increasing levels of casein up to 25% and the breakpoint was found at 24% intact protein, indicating that the levels of indispensable amino acids (IDAA) supplied by the 24% intact protein were sufficient to meet the requirements of trout for IDAA. Results suggested that energy sources used for trout diets play an important role in the determination of the protein requirements, and that the conventionally established protein requirement (40%) includes protein required to meet IDAA requirements (24%) and that required to meet energy needs (16%).

Requirements for sulfur amino acids and utilization of D-methionine by rainbow trout (Oncorhynchus mykiss)

Abstract The methionine (Met) requirement and replacement values of cystine (Cys) and D-Met for L-Met were estimated at 15 °C for fingerling rainbow trout ( Oncorhynchus mykiss ) by feeding diets containing various levels of L-Met, D-Met and L-Cys. Four tanks, each containing 28 (Experiment 1) or 30 (Experiment 2) trout (11–15 g initial weight), were assigned to each diet. Weight gain and nitrogen retention during a 6-week period increased with increasing levels of L-Met up to 0.5% of diet, when the diets contained excess L-Cys (0.5%). Feed efficiency increased as L-Met increased, but no significant ( P > 0.05) differences were detected at levels above 0.4%. With diets containing 0.5% L-Met, the Cys requirement was found to be 0.3% of the diet. Increasing D-Met level above 0.27% in a diet containing 0.23% L-Met did not significantly ( P

Effect of fasting or feeding diets containing different levels of protein or amino acids on the activities of the liver amino acid-degrading enzymes and amino acid oxidation in rainbow trout (Oncorhynchus mykiss)

Abstract Experiments were done on fingerling rainbow trout at 15 ± 1 °C to determine the effect of: (1) fasting or feeding diets containing different levels of protein on liver glutamate dehydrogenase (GDH), alanine aminotransferase (AAT) and histidase activities; (2) dietary protein level on the oxidation rates of glutamate and phenylalanine in vivo; and ( 3 ) dietary phenylalanine level on the phenylalanine oxidation rate in vivo. Activities of GDH and AAT per g liver or per g protein were higher (P The oxidation rates of dietary glutamate and phenylalanine in trout that had previously been fed the 35% protein diet, were about three and five times those found in fish previously fed the 10% protein diet, respectively. This difference was found when fish that had been fed the 10 or 35% protein diet were subsequently fed the 35% protein diet containing14C-labeled glutamate or phenylalanine, indicating that trout previously fed a high protein diet have a greater capacity to catabolize these amino acids. The oxidation rate of dietary glutamate was approximately five or nine times that of phenylalanine in trout fed diets containing 35 or 10% protein, respectively. The rate of phenylalanine oxidation increased with increasing phenylalanine levels in the diet; no break point or plateau in the dose-response curve was observed. Our studies demonstrated that fasting or feeding a high protein diet increases the amino acid catabolism in trout, and suggested that the amino acid oxidation technique cannot be used to determine the amino acid requirements of trout.

Effects of dietary tryptophan levels on growth, feed/gain, carcass composition and liver glutamate dehydrogenase activity in rainbow trout (Salmo gairdneri)

1. The tryptophan requirement of rainbow trout (initial body wt, 13 g) was estimated by feeding diets containing varied levels of tryptophan from 0.06 to 0.5% of diet for 6 weeks. 2. The estimated tryptophan requirement was 0.20-0.25 (0.57-0.71)% of diet (dietary proteins). 3. Nitrogen retention increased and feed/gain decreased with dietary tryptophan levels up to 0.14%, but no further effect was observed at levels above 0.14%. 4. Carcass protein content gradually increased and lipid and ash contents decreased with increasing dietary tryptophan levels. 5. Dietary tryptophan levels did not affect hepatosomatic index or liver glutamate dehydrogenase activity.

Re-evaluation of protein and amino acid requirements of rainbow trout (Oncorhynchus mykiss)

Abstract Work on protein and amino acid requirements of rainbow trout, previously done at the University of Wisconsin, Aquaculture Research Laboratory, was re-evaluated with the view that the requirements are not much different from those of other rapidly growing farm animals. Most fish species are carnivorous and are adapted to use protein as a preferred energy source over carbohydrate, and thus require high levels of dietary protein (30–60%). Rainbow trout were found to utilize a dispensable amino acid (DAA) mixture or alanine alone as effectively as casein as an energy source. When a DAA mixture was used as a substitute for casein in a diet containing 2% gelatin and casein supplemented with arginine and methionine, the level of dietary protein needed to meet the indispensable amino acid (IDAA) requirements was found to be about 24%. This level is not different from that for baby pigs as recommended by the National Research Council. The levels of IDAA in the 24% protein diet exceeded the IDAA requirements of rainbow trout estimated to date. The estimated requirements (vs the contents in the 24% protein diet) for lysine, sulfur amino acids, tryptophan, aromatic amino acids and arginine were 1.3 (1.9), 0.8 (0.98), 0.2 (0.28), 1.5 (2.5) and 1.4 (1.6)% of diet, respectively. These values are comparable to those recommended for baby pigs except for arginine: 1.4, 0.68, 0.2, 1.1 and 0.6%, respectively. Results indicate that the requirements of rainbow trout for protein and amino acids are not much different from those of other rapidly growing farm animals.

Requirement for phenylalanine and replacement value of tyrosine for phenylalanine in rainbow trout (Oncorhynchus mykiss)

Abstract The requirement for phenylalanine (Phe) and replacement value of tyrosine (Tyr) for Phe in fingerling rainbow trout were determined by feeding diets containing various levels of Phe and Tyr. Four tanks of 30 trout each were assigned per diet and fed 3 times daily to satiation at 15°C. With diets containing excess Tyr (1.33%) and 35% crude protein, weight gain of 13-g trout over a 6-week period increased linearly with increasing levels of Phe up to 0.75% of dry diet but was not different ( P >0.05) at 0.75% and 1.75% Phe. Feed efficiency and nitrogen retention improved as Phe level in the diet increased up to 0.55%, but no significant effects were found at levels above 0.55%. Carcass protein content increased with Phe level up to 0.65% and fat content decreased concurrently. Increasing Tyr level up to 0.7% in a diet containing 0.6% Phe increased weight gain of 14-g trout over a 6-week period, but a further increase in Tyr level to 0.8% had no effect ( P >0.05). Analysis of data using a broken-line model showed that the Phe requirement of fingerling rainbow trout is 0.7±0.05% (mean±s.e.) of dry diet or 2.0% of dietary protein, when a diet contains excess Tyr and 35% protein, and that the replacement value of Tyr for Phe is approximately 53% on a weight basis or 48% on a molar basis. Thus the total aromatic amino acid requirement is 1.5% of dry diet or 4.3% of dietary protein.