Long-term evaluation of extruded diets compared with raw fish moist diet for growing Korean rockfish, Sebastes schlegeli (Hilgendorf)

A long‐term experiment was conducted in sea cages to compare three experimental extruded pellet (EP) diets with a raw fish moist pellet (MP) diet for Korean rockfish, Sebastes schlegeli (Hilgendorf). White fishmeal (WFM), soybean meal (SM) and fishmeal analogue (BAIFA‐M?)‐based experimental EP diets were formulated to be isonitrogenous and isocaloric with 50% crude protein (CP) with available energy of 16.7 kJ g^?1 diet. An MP diet made of 80% frozen horse mackerel + 20% commercial binder meal was also included in the experiment. The proportions of the major protein ingredients in three experimental EP diets were as follows: WFM diet, 100% WFM; SM diet, 70% WFM + 30% SM; BAIFA‐M? diet, 70% WFM + 30% BAIFA‐M?. The experiment was divided into three periods according to fish size: period I, initial weight of 20.2 ± 3.6 g (mean ± SD); period II, initial weight of 57.6 ± 4.7 g (mean ± SD); period III, initial weight of 96.3 ± 6.9 g (mean ± SD). There were no significant differences in weight gain, feed efficiency ratio, thermal‐unit growth coefficient, specific growth rate, haemoglobin, or haematocrit among fish that were fed the four diets during all three periods. However, fish that were fed the MP diet had a lower survival rate than the fish that were fed the other three EP diets for all periods. These results strongly suggest that EP diets could be developed to replace MP diet for the grow‐out stage of production of Korean rockfish without adverse effects on growth performance.     

Dietary dehulled soybean meal as a replacement for fish meal in fingerling and growing olive flounder Paralichthys olivaceus (Temminck et Schlegel)

Two experiments were conducted to determine the optimum dietary inclusion level of dehulled soybean meal (DHSM) as a fish meal (FM) replacement in diets for olive flounder Paralichthys olivaceus. All the experimental diets were formulated to be isonitrogenous and isoenergetic to contain 50% crude protein (CP) and 16.7 kJ energy g^?1 diet. In the first experiment, eight diets were formulated to replace FM with DHSM at 0%, 10%, 20% without amino acid (AA) supplementation; 20%, 30%, 40% with AA supplementation and 30%, 40% with AA & attractant supplementation (DHSM₀, DHSM₁₀, DHSM₂₀, DHSM_20+AA, DHSM_30+AA, DHSM_30+AA+Att, DHSM_40+AA, DHSM_40+AA+Att respectively). Triplicate groups of 25 fish averaging 5.0±0.04 g (mean±SD) were fed one of eight experimental diets for 8 weeks. In the second experiment, six diets were formulated to replace FM with DHSM at 0%, 10%, 20%, 30% without attractant supplementation and 20%, 30% with attractant supplementation (DHSM₀, DHSM₁₀, DHSM₂₀, DHSM₃₀, DHSM_20+Att, DHSM_30+Att respectively). Triplicate groups of 15 fish averaging 45.5±0.08 g (mean±SD) were fed one of six experimental diets for 10 weeks. Based on growth performance, we concluded that DHSM could replace FM up to 20% without AAs (lysine and methionine) and attractant supplementation, and up to 30% with AAs and/or attractant supplementation in diets for fingerling and growing olive flounder.     

Effects of dietary protein levels on growth performance and body composition of juvenile parrot fish, <Emphasis Type="Italic">Oplegnathus fasciatus</Emphasis>

The present study was conducted to evaluate the effects of dietary protein levels on growth, biometrics, hematology and body composition in juvenile parrot fish Oplegnathus fasciatus. Fish averaging 7.1 ± 0.06 g (mean ± SD) was randomly distributed into 15 net cages (each size: 60 × 40 × 90 cm, W × L × H) as groups of 20 fish. Five isocaloric diets (16.7 kJ/g energy) were formulated to contain crude protein levels (CP) as 35 (CP₃₅), 40 (CP₄₀), 45 (CP₄₅), 50 (CP₅₀) and 60 % (CP₆₀) in the diets. Fish were fed one of the experimental diets at apparent satiation twice a day in triplicate groups. At the end of 8-week feeding trial, weight gain (WG) of fish fed with CP₅₀ and CP₆₀ diets were significantly higher than those of fish fed with CP₃₅, CP₄₀ and CP₄₅ diets. Fish fed with CP₄₅, CP₅₀ and CP₆₀ diets had higher feed efficiency (FE) and specific growth rate (SGR) than those of fish fed with CP₃₅ and CP₄₀ diets. Protein retention efficiency (PRE) decreased with increase of dietary protein levels among fish fed with the experimental diets. Whole-body crude protein and lipid contents increased with the dietary protein level up to CP₅₀ diet. In conclusion, analysis of variance (ANOVA) revealed that the optimum dietary protein level could be 50 % for maximum growth of juvenile parrot fish, while the broken-line analysis of WG suggested that the level could be 48.5 %, in a diet containing 16.7 kJ/g energy.     

Reevaluation of the Phosphorus Requirement of Juvenile Olive Flounder Pavalichfhys olivaceus and the Bioavailability of Various Inorganic Phosphorus Sources

A 6‐wk feeding trial was conducted to reevaluate the phosphorus (P) requirement of juvenile olive flounder and the bioavailability of various inorganic phosphorus sources (IPS). Eight experimental diets were prepared such that all diets contained the same amount of calories, nitrogen, and calcium. Each diet included 0.33% total phosphorus (TP) and 0.60 % total calcium supplied by the basal diet. The eight experimental diets were: the basal diet without P supplementation (BD), three diets consisting of the BD supplemented with NaH,PO₄.2H₂O (NaP_0.45 NaP_0.57 or NaP_1.14) to supply 0.45, 0.57 or 1.14% TP, and four diets consisting of the BD supplemented with K₂HPO₄ (KP_0.57), Ca(H₂PO₄)_;H₂O (Cap_0.57), CaH₂PO_4;2H₂O (CaHP_0.57) or flounder bone meal (FBP_0.57) to supply 0.57% TP. Fish (N = 480)averaging 4.02 ± 0.03 g (Mean ± SD) were distributed randomly into 24 aquaria (20 fish per aquarium), and were fed one of the eight experimental diets in triplicate groups. The weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) of fish fed the NaP_0.57 diet were significantly higher than those of fish fed the BD, NaP_1.14, KP_0.57, CaHP_0.57 and FBP_0.57 diets (P > 0.05). There was no significant difference in WG, SGR, PER, and FER among fish fed the Nap_0.45, NaP_0.57 and Cap_0.57, diets. Whole body P retention (WBP_ret) in fish fed the Nap_0.57 diet was significantly higher than in fish fed the BD, NaP_1.14, KP_0.57 CaHP_0.57 and FBP_0.57diets (P > 0.05). There was no significant difference in WBP_ret among fish fed the NaP_0.47, NaP_0.57, and CaP_0.57, diets. The ability of the fish to digest the phosphorus in the NaP_0.45, Nap_0.57, NaP_1.14, and CaP_0.57 diets was significantly better than that of fish fed the other diets (P > 0.05). These results indicated that the dietary P requirement for juvenile olive flounder could be 0.45457%. Also, NaH,PO_; 2H₂O and Ca(H₂PO₄)_;H₂O appeared to have a better bioavailability than the other P sources in juvenile olive flounder.     

Effects of Dietary Chlorella ellipsoidea Supplementation on Growth, Blood Characteristics, and Whole-Body Composition in Juvenile Japanese Flounder Paralichthys olivaceus

The study was conducted to investigate the effects of dietary Chlorella powder (C) supplementation on growth performance, blood characteristics, and whole-body composition in juvenile Japanese flounder Paralichthys olivaceus . Four experimental diets were supplemented with C at 0, 1, 2 and 4% (C₀, C₁, C₂, and C₄) on a dry-weight basis. Three replicate groups of fish averaging 1.13 ± 0.02 g (Mean ± SD) were randomly distributed in each aquarium and fed one of four experimental diets for 12 wk. After 12 wk of the feeding trial, fish fed C₂ diet had higher weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) than did fish fed C₀ and C₁ diets ( P 0.05); however, there was no significant difference among fish fed C₁ and C₄ diets, and among fish fed C₂ and C₄ diets ( P > 0.05). Fish fed C₂ and C₄ diets had a lower serum cholesterol level than did fish fed C₀ and C₁ diets ( P 0.05). Fish fed C₂ and C₄ diets had a lower body fat than did fish fed C₀ ( P 0.05). These results indicate that dietary supplementation of 2% Chlorella powder in the commercial diets could improve growth, feed utilization, serum cholesterol level, and whole-body fat contents in juvenile Japanese flounder.     

Evaluation of optimum dietary protein-to-energy ratio in juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

An 8‐week feeding trial was conducted to estimate the optimum dietary protein to energy (P/E) ratio in juvenile olive flounder Paralichthys olivaceus. Eight experimental diets were formulated with two energy levels and four protein levels at each energy level. Two energy levels of 12.5 and 16.7 kJ g^?1 diets were included at crude protein (CP) levels of 25%, 30%, 35% and 45% with 12.5 kJ g^?1, and CP levels of 35%, 45%, 50% and 60% with 16.7 kJ g^?1. After 1 week of the conditioning period, fish initially averaging 8.1±0.08 g (mean±SD) were randomly distributed into the aquarium as groups of 15 fish. Each diet was fed on a dry‐matter basis to fish in three randomly selected aquariums at a rate of 3–5% of total wet body weight per day for 8 weeks. After 8 weeks of the feeding trial, weight gain (WG), feed efficiency ratio and specific growth rate of fish fed 45% CP with 16.7 kJ g^?1 energy diet were significantly higher than those from the other dietary treatments (P<0.05). WG of fish fed 12.5 kJ g^?1 energy diets increased with the increase of dietary protein levels. However, WG of fish fed 16.7 kJ g^?1 energy diets increased with the increase of dietary protein levels up to 45% CP and then decreased when fish fed 50% and 60% CP diets. Both dietary protein and energy affected protein retention efficiency and energy retention efficiency. Haemoglobin (Hb) of fish fed 35% and 45% CP diets with 12.5 kJ g^?1 energy were significantly high and not different from Hb of fish fed 45% and 50% CP diets with 16.7 kJ g^?1 energy. Haematocrit of fish fed 45% CP diet with 16.7 kJ g^?1 energy was significantly higher than those from fish fed 25% and 30% CP diets with 12.5 kJ g^?1 energy (P< 0.05). Based on the results of this experiment, we concluded that the optimum dietary P/E ratio was 27.5 mg protein kJ^?1 with diet containing 45% CP and 16.7 kJ g^?1 energy in juvenile olive flounder.     

Effects of Dietary Recombinant Bovine Somatotropin Levels on Growth, Plasma Recombinant Bovine Somatotropin Concentrations, and Body Composition of Juvenile Korean Rockfish, Sebastes schlegeli

This experiment was conducted to study the effects of the graded recombinant bovine somatotropin (rBST) levels on growth, plasma rBST concentrations, and body composition of Korean rockfish, Sebastes schlegeli, and to estimate the optimum oral dosage of rBST. Seven experimental diets were formulated to be isonitrogenous and isocaloric and to contain 49.0% crude protein and 16.7 kJ available energy/g, with 0, 5, 10, 15, 20, 25, or 50 mg rBST/kg body weight (BW)/wk (rBST₀, rBST₅, rBST₁₀, rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀, respectively). After the feeding trial, fish fed all the diets supplemented with rBST showed higher weight gain (WG), feed efficiency (FE), specific growth rate (SGR), and protein efficiency ratio (PER) than those fed the rBST₀ diet (P < 0.05). WG of fish fed rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets was significantly higher than that of fish fed rBST₀ and rBST₅ diets (P < 0.05); however, there were no significant differences among fish fed rBST₁₀, rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets. FE of fish fed rBST₁₅ and rBST₂₀ diets was significantly higher than that of fish fed rBST₀, rBST₅, rBST₁₀, and rBST₅₀ diets, and fish fed rBST₁₀, rBST₂₅, and rBST₅₀ diets had significantly higher FE than those fed rBST₀ and rBST₅ diets (P < 0.05). SGR of fish fed all the diets supplemented with rBST was significantly higher than that of fish fed rBST₀ diet (P < 0.05); however, there were no significant differences among fish fed all the diets supplemented with rBST. PER of fish fed rBST₁₅ and rBST₂₀ diets was significantly higher than that of fish fed rBST₀, rBST₅, and rBST₅₀ diets, and fish fed rBST₁₀, rBST₂₅, and rBST₅₀ diets had significantly higher PER than those fed rBST₀ and rBST₅ diets (P < 0.05). Whole‐body protein of fish fed rBST₁₅ diet was significantly higher than that of fish fed rBST₀, rBST₅, and rBST₁₀ diets (P < 0.05); however, there were no significant differences among fish fed rBST₁₅, rBST₂₀, rBST₂₅, and rBST₅₀ diets. Plasma rBST concentrations of fish fed all the diets began to rise at 3 h after oral administration of rBST; the maximum plasma rBST concentration peaked at 12 h and returned to the basal level at 24 h. Broken‐line model analyses of WG and FE were 12.8 and 13.2 mg rBST/kg BW/wk, respectively. These results indicated that the optimum oral dosage could be greater than 12.8 mg rBST/kg BW/wk but less than 13.2 mg rBST/kg BW/wk in juvenile Korean rockfish.     

Evaluation of l-ascorbyl-2-glucose as the source of vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf)

This study was conducted to compare l ‐ascorbyl‐2‐glucose (AA2G) with l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish Sebastes schlegeli (Hilgendorf). Fish were fed one of seven semi‐purified diets containing equivalents of 0, 50, 100 and 200 mg ascorbic acid (AA) kg^?1 diet in the form of AA2G or AMP‐Na/Ca for 12 weeks. After 12 weeks of feeding, weight gain, feed efficiency ratio and survival of fish fed the vitamin C‐free diet were significantly lower than those of fish fed the vitamin C‐supplemented diets in either form. The hepatosomatic index, condition factor and survival of fish fed AMP‐Na/Ca₁₀₀, AMP‐Na/Ca₂₀₀, AA2G₁₀₀ and AA2G₂₀₀ diets were significantly higher than fish fed the vitamin C‐free diet. After 9 weeks of feeding, fish fed the vitamin C‐free diet began to show vitamin C deficiency signs such as anorexia and lethargy. At the end of the 12‐week feeding trial, fish fed the vitamin C‐free diet exhibited vitamin C deficiency signs, e.g., anorexia, scoliosis, exophthalmia and fin haemorrhage. Vitamin C retention in the muscle and liver was similar to those of fish fed AA2G‐ or AMP‐Na/Ca‐supplemented diets. In general, there was no significant difference in the muscle and liver vitamin C concen‐tration in fish fed the AA2G and AMP‐Na/Ca diets at the same supplementation levels.     

Evaluation of different <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> extracts as feed additives for growth and immunity of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

We evaluated the effects of diets incorporating the red algae Pyropia yezoensis, prepared by several different extraction methods, on the growth of juvenile Japanese flounder Paralichthys olivaceus. We assessed growth performance, as well as the levels of amino acids, fatty acids, insulin-like growth factor I (IGF-I) and interleukins (ILs). Four experimental diets were developed based on different methods of processing P. yezoensis. A commercial feed, laver powder (P), high-pressure heat extraction of laver (HPHE) and acid hydrolysis extraction of laver were used as the experimental diets. Three experimental replicates were established for each diet (40 fish/group, body weight 123.7 ± 1.1 g), and the fish were fed for 6 weeks. We found no significant differences in weight gain, specific growth rate or feeding efficiency among the groups (P > 0.05); however, the fish fed HPHE had the greatest growth performance. Fish fed the laver extracts exhibited the highest protein efficiency ratio compared with the control and P groups. The experimental groups fed P. yezoensis extracts had significantly higher levels of IGF-I (P < 0.05) than those of the control group. High levels of IL-2 were found in the P and HPHE groups, IL-12 in the HPHE group, and IL-6 in all experimental groups. Therefore, these results suggest that a P. yezoensis extract improved the growth performance and immunity of Japanese flounder. In particular, the high-pressure heating process was a useful extraction method for preparing a P. yezoensis extract, which had beneficial effects as a dietary supplement in Japanese flounder.