Takeshi Murai

The Influence of Dissolved Oxygen on the Growth of Channel Catfish

Abstract The long-term effects of three levels of dissolved oxygen (100, 60 and 36% of air saturation) on channel catfish, Ictalurus punctatus, were evaluated under two feeding regimes—a constant rate of 3% of biomass daily and ad libitum. At ad libitum rates (6-week duration) average gains of 159, 124, and 65 g per fish were obtained in tanks containing oxygen at 100, 60 and 36% of saturation, respectively. In both experiments food consumption and efficiency were drastically reduced at 36% oxygen saturation. Survival rates were 100% in all groups, thus suggesting that disease and parasite problems were not enhanced by a hypoxic environment. In these studies catfish did not demonstrate a polycythemic response to hypoxic conditions.

Effects of amino acid supplementation and methanol treatment on utilization of soy flour by fingerling carp

Effects of crystalline amino acid supplementation and methanol treatment on utilization of soy flour by fingerling carp, Cyprinus carpio, were studied in a 4-week feeding trial. Fish fed diets in which 75% of the fish meal was isonitrogenously replaced with methanol-treated or untreated soy flour achieved almost a 350% weight gain in 4 weeks if the test diets were supplemented with essential amino acids to the levels in a fish meal-torula yeast control diet. This is approximately 90% of the value attained by the control group. However, feed efficiency and percentage of protein deposition of the test groups were slightly but significantly lower than those of the control group. Methanol treatment failed to show any effect on perfomance of the carp. Neither essential amino acid supplementation nor methanol treatment of soy flour had any effect on whole body proximate composition of carp. The only significant difference noted in the plasma amino acid levels of carp at 6 h post-feeding was methionine among the dietary treatments. Fish performance was more closely correlated to the amino acid profiles of plasma than those of the diets. Therefore, the former was far superior to the latter for evaluation of protein quality in a diet supplemented with crystalline amino acids.

Protein nutrition of rainbow trout

Abstract One of the ultimate goals of protein nutrition is formulation of high quality and yet cost effective feed with efficient utilization of alternative protein sources. Although the rainbow trout is one of the most popular experimental fish, contradictory results on protein nutrition have been reported by different workers. This review summarizes the progress made in studies on amino acid metabolism, factors affecting protein requirements and alternative protein sources, emphasizing unique aspects of rainbow trout on these subjects. The possible reasons for the discrepancy reported in amino acid requirements of rainbow trout are briefly discussed.

Supplementation of methionine to soy flour diets for fingerling carp, Cyprinus carpio

Abstract A 6-week feeding study was conducted to determine whether methionine (Met) alone is sufficient as a supplemental amino acid for a soy flour based diet and to assess whether increasing supplemental levels of Met would further improve nutritional value of soy flour for fingerling carp. The combinations of supplemental amino acids employed were: (1) essential amino acids without Met (EAA mix); (2) the EAA mix with either low (0.25%) or high (0.50%) levels of Met; (3) a non-essential amino acid mix (NEAA mix); (4) the NEAA mix plus 0.25% Met. The protein sources used for the experimental diets were 10.5% fish meal, 13.6% torula yeast and 41.2% soy flour. Supplementation with the EAA mix alone did not improve growth, protein deposition and feed efficiency. However, a combination of 0.25% Met with either the EAA mix or NEAA mix improved these parameters significantly. The addition of 0.50% Met even in combination with the EAA mix depressed the performance of carp to the level of fish fed diets without Met supplementation. Six-hour-postprandial levels of free Met were noted to decline in the viscera and rise in the plasma and muscle as the dietary concentration of Met was increased. By contrast, levels of taurine (Tau) and methionine sulfoxide (Mso) were directly related to dietary Met levels observed in the viscera. Supplementation of the EAA mix did not markedly affect free EAA concentrations in the aforementioned tissues and plasma except for histidine (His). These findings indicate that the basal soy flour diet was deficient in Met and supplementation of 0.25% Met alone is sufficient. Also a high level of Met supplementation (0.50% in this study which made total Met content equivalent to 130% of the requirement for carp) was not beneficial and stimulated Met degradation to Tau and Mso. Thus, these results suggest that it is important to optimize the supplemental level of Met when crystalline amino acids are used to adjust amino acid balance in a diet for fingerling carp.

Supplementation of various meals to fish meal diet for chum salmon fry

Abstract In a 6-week feeding experiment, chum salmon, Oncorhynchus keta , swim-up fry, were fed fish meal diets supplemented with silkworm pupae powder (5%), dried beef liver (5%), krill meal (5%) or earthworm powder (5%) at the expense of fish meal, or substituting glucose (13%) for dextrin. Fish fed the diet with earthworm powder showed the best growth performance (675% weight gain in 6 weeks) and feed efficiency (117%). The growth rate and feed efficiency of the krill meal group were also significantly better than those of the control group (without supplement or substitution). Substitution of glucose and supplementation of silkworm pupae or beef liver failed to improve the growth rate, but significantly improved feed efficiency. Food consumption of fish fed the diet supplemented with earthworms was lowest, and none of the dietary treatments appreciably increased food intake of the fish over that of the control group. The dietary group receiving earthworm powder also showed significantly higher body fat content than the remaining dietary groups. No significant differences were noted in body protein and ash contents among all dietary treatments.

White muscle of masu salmon, Oncorhynchus masou masou, smolts possesses a strong buffering capacity due to a high level of anserine

Masu salmon, Oncorhynchus masou masou, fry were fed with diets containing three different levels of protein for 18 weeks, and the levels of free amino acids and related compounds in the white muscle were compared among the dietary groups and between smolts and parr. The anserine level in the white muscle of smolts was always higher than that of parr, while histidine and glycine levels in the former were always lower than those in the latter, irrespective of dietary treatments. A mixed solution of crystalline anserine, histidine and glycine simulating these amino acid levels in the white muscle of the smolts had a stronger buffering capacity in the physiological pH range than that simulating those levels present in parr. These results suggest that even in freshwater conditions, the white muscle of smolts possesses a more potent buffering capacity than the muscle of parr, for anaerobic burst swimming during the downstream migration. Moreover, the white muscle of smolts fed the high-protein diet had a significantly higher level of anserine than that of smolts fed the low- or intermediate-protein diets, and the solution mimicking the white muscle of smolts fed the high-protein diet showed the strongest buffering capacity among the mixed solutions tested. Thus, a diet with high-protein level could improve qualities of smolts.

Growth, feed efficiency and feed intake of offspring from selected and wild Japanese flounder (Paralichthys olivaceus)

Abstract Feeding and starvation trials were conducted to investigate the nutritional trait differences between the offspring from broodstock under selective improvement for growth for two generations and wild-caught broodstock of the Japanese flounder. In the feeding trial, juveniles (initial mean body weight: 13.7 g for the selected line and 14.5 g for the wild line, 25 fish/tank, triplicate groups) from both broodstock were fed with either 61.4% crude protein–14.1% lipid diet (dry basis, diet 1) or 60.3% crude protein–16.4% lipid diet (dry basis, diet 2) for 6 weeks. Two-way analysis of variance (ANOVA) revealed that the selected line had significantly higher final body weight, weight gain and feed intake than the wild line irrespective of the dietary treatment. When the size effect was removed by analysis of covariance (ANCOVA), the selected line had superior feed efficiency and higher feed intake than the wild line regardless of the dietary treatment. Body lipid and energy contents were significantly higher in the selected line than in the wild line though energy retention was not significantly different between the lines. Feeding diet 2 (with a slightly higher dietary lipid level) positively affected protein and energy retention in the selected line without growth retardation. There was no effect of diet on these traits in the wild line. In the 2-week starvation trial, there were no noticeable differences in protein, lipid and energy expenditures between the lines. The results of the present study demonstrate that the selected line of the Japanese flounder had superior growth rate and greater feed intake and that the improved growth rate was associated with better feed efficiency. Moreover, the results suggest that many nutritional parameters were influenced by genetic factors in Japanese flounder.

Growth performance and macronutrient retention of offspring from wild and selected red sea bream (Pagrus major)

Abstract Two experiments were conducted to investigate nutritional trait differences between offspring from red sea bream selected for increased growth rate for four generations and offspring from wild-caught red sea bream. In experiment 1, juveniles (5.6 g, 30 fish/tank, triplicates) of both lines were fed low-lipid (17.1% lipid, 58.2% protein, by dry basis) or high-lipid (26.0% lipid, 52.4% protein, by dry basis) diets by hand, twice daily to approximate satiation for 6 weeks. The selected line had higher feed intake (g/fish/6 weeks and %/wet biomass/day) and weight gain than the wild line, regardless of the dietary treatment. However, the selected line converted feed less efficiently than the wild line. The selected line had lower body protein content and body protein retention and higher body lipid content than the wild line, regardless of the dietary treatment. Body energy content (kJ/g) was higher in the selected line than in the wild line, though the energy retention was not significantly different between the lines. The selected line had higher visceral adipose mass and visceral adiposomatic index than the wild line. The dietary treatments affected feed intake, growth, feed efficiency and body protein retention. Significant interactions of line×diet were not found for any parameter. In experiment 2, fish (46 g in the selected line, 34 g in the wild line) from the same sources as experiment 1 were starved under resting or swimming condition for 14 days to compare protein and lipid expenditures. The selected line decreased body protein content during starvation under both conditions, while the protein content did not change in the wild line. Body lipid content decreased under swimming condition but not resting condition, irrespective of the lines. As overall traits, the selected line had higher feed intake and growth rate without improved feed efficiency, compared with the wild line. Moreover, the selected line seemed to consume protein rather than lipid as the energy source and have a higher ability to build fat deposits than the wild line.

Effects of dietary fatty acid composition on growth and smolting of underyearling masu salmon, Oncorhynchus masou

Abstract A 20-week feeding experiment was conducted to study the effects of dietary fatty acid composition on growth and smolting of underyearling masu salmon, Oncorhynchus masou, using purified test diets. Partial replacement of basal lipid (5% palmitate and 5% oleate) with a mixture of linoleate and linolenate improved the % weight gain and feed efficiency by 220% and 160%, respectively, over those of fish fed the basal diet. This treatment also distinctly improved the rate of smolt production. By contrast, partial replacement of the basal lipid with linoleate alone failed to show any effects on performance of the fish. These results suggest that dietary fatty acid composition not only influences growth but also smolting. Proportions of long-chain polyunsaturated fatty acids in the polar lipids of the smolts were relatively higher than those of the parr, when the fish were fed the purified test diet. The fatty acid composition of the smolts resembled the typical seawater lipid pattern, even though they were reared under freshwater conditions.

Pantothenic Acid Supplementation of Diets for Catfish Fry

Abstract Two studies were conducted with channel catfish fry (Ictalurus punctatus) fed diets containing four levels of pantothenic acid activity (10, 25, 66, and 250 mg/kg diet). Supplemental pantothenate markedly improved growth rate, survival, and feed conversion, and prevented a loss of appetite, clubbed gills, and sluggishness. The results of these experiments suggest that diets fed to catfish fry should contain at least 250 mg of pantothenic acid per kg of diet.