Specific Growth Rate Of Fish Research Articles

Spirulina as a natural carotenoid source on growth, pigmentation and reproductive performance of yellow tail cichlid Pseudotropheus acei

A feeding trial on yellow tail cichlid Pseudotropheus acei (Regan 1922) was undertaken to asses the effect of dietary Spirulina meal as a natural carotenoid source. Four experimental diets were formulated to progressively replace 0% (C), 2.5% (SP2.5), 5% (SP5) and 10% (SP10) of fish meal weight. Ten fish per tank (initial weight 3.75 ± 0.02 g) were randomly distributed into twelve 80 l fiberglass tanks connected to a closed recirculation system (temperature 26.7 ± 0.06°C). The diets were tested in triplicate for 12 weeks. The specific growth rate of fish fed all Spirulina diets were significantly higher compared to diet C. Feed intake (FI) tended to increase with dietary Spirulina level, and fish fed diet SP10 had significantly higher FI values compared to diet C. No significant differences in feed conversion ratio were observed among these groups. Although the protein efficiency ratio of fish fed diet C was lower than that of all Spirulina diets, no significant differences were observed among these groups (P > 0.05). The total egg production and hatching rate (%) of eggs derived from all fish fed with Spirulina diets was significantly higher compared those from fish fed diet C. The yellow and blue coloration of yellow tail cichlid fed the diet containing Spirulina meal was enhanced and inclusion of dietary Spirulina meal was elevated carotenoids in skin. Results of the present study indicated that Spirulina meal has the potential to enhance the growth, reproductive performance and coloration on yellow tail cichlid.

Evaluation of Nitrogen and Phosphorus Wastes Produced by Nile Tilapia (<i>Oreochromis niloticus</i> L.) Fed <i>Azolla</i>-Diets in Earthen Ponds

Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2% crude protein) and isoenergetic (16.9 Kj·g–1) diets A0, A10, A20, A30, A40 and A50, containing 0%, 10%, 20%, 30%, 40% and 50% of Azolla meal (AM) respectively, as partial fishmeal (FM) substitutes, was provided to experimental fish. The Azolla-free diet A0 served as a control. Fish specific growth rate (SGR) was higher with the control diet, the lower values being obtained in A50-fed fish (P Azolla could be used in diet to sustain Nile tilapia growth and as “environmentally-friendly” ingredient to limit P loss, while providing N to the field, beneficially in tropical marshland pond where this nutrient is already limiting.

Compensatory Growth of Grower Olive Flounder (Paralichthys olivaceus) with Different Feeding Regime at Suboptimal Temperature.

Compensatory growth of grower olive flounder (Paralichthys olivaceus) was determined at suboptimal temperature (13.0±1.9°C). Fifteen fish averaging 201.1 g per tank were distributed into 18 of 300 L flow-through tanks. Six treatments were prepared in triplicate: fish were hand-fed with an extruded pellet to apparent satiation once a day for 16 weeks (16 WF); and the other five groups of fish were hand-fed for 15, 14, 13, 12 and 10 weeks after 1-, 2-, 3-, 4- and 6-week feed deprivation, referred to as 15 WF, 14 WF, 13 WF, 12 WF and 10 WF, respectively. A linear relationship between body weight of fish and feed deprivation was observed: Y (Body weight of fish) = −1.81X (Weeks of feed deprivation)+201.07, R2 = 0.83. Weight gain of grower olive flounder in 15 WF, 14 WF, 13 WF and 12 WF treatments was comparable to that of fish in 16 WF treatment, but lower than that of fish in 10 WF treatment. Specific growth rate of fish in 15 WF treatment was higher than that of fish in 16 WF, 14 WF and 10 WF treatments. Feed consumption of fish was not affected by feeding regime. Feed and protein efficiency ratios of fish in 15 WF treatment were higher than those of fish in 13 WF, 12 WF and 10 WF treatments. Grower olive flounder could achieve full compensatory growth when fish were daily fed for 12 weeks after 4-week feed deprivation at suboptimal temperature.

Compensatory growth response of European sea bass (Dicentrarchus labraxL.) under cycled starvation and restricted feeding rate

The compensatory growth response of the European sea bass (Dicentrarchus labrax) that faced cycling starvation and restricted ration was assessed. Juveniles (10.5 g) were stocked into 15 tanks at a density of 25 fish per tank. Five different feeding regimes were tested on triplicate groups of fish: CSatiation: control fed for 60 days without deprivation, CRestricted: 25% restricted feeding, S-R: 1 day starvation then 4 days CRestricted feeding, R-F: 1 day CRestricted feeding then 4 days CSatiation feeding, and, finally, S-F: 1 day starvation then 4 days CSatiation feeding. The specific growth rate of fish in the CSatiation (2.5 ± 0.06% day−1), S-F (2.5 ± 0.11% day−1) and R-F (2.4 ± 0.18% day−1) were significantly higher than that of CRestricted (2.2 ± 0.05% day−1) or S-R (2.0 ± 0.01% day−1). Fish in S-F group were able to achieve catching up with the CSatiation. There was no significant difference in feed conversion rates but R-F and S-F consumed approximately 34% more feed than CSatiation following the first re-feeding day. Although, the highest lipid content was observed in CSatiation (14.4%), S-R (33.3% dry matter) had the highest water content compared with the CSatiation and CRestricted (37.8% and 36.9% dry matter respectively). In conclusion, it may be concluded that sea bass has rapid response to cycling starvation/re-feeding and that a 25% restricted feeding ratio is insufficient to invoke a compensatory growth response in sea bass.

Response of dietary substitution of fishmeal with various protein sources on growth, body composition and blood chemistry of olive flounder (Paralichthys olivaceus, Temminck & Schlegel, 1846)

Animal and/or plant protein sources substituting fishmeal in the diets keep being developed due to its high price. The purpose of this study is to determine response of dietary substitution of fishmeal with silkworm pupae meal, promate meal®, meat and bone meal and/or their combination on the performance of juvenile olive flounder. A 60% fish meal was used as the main protein source, used as the control (Con) diet. The 10 and 20% fishmeal were substituted with silkworm pupae meal and meat and bone meal, referred to as the SPM10, SPM20, MBM10 and MBM20 diets, respectively. And the 10, 20 and 40% fishmeal were substituted with promate meal®, referred to as the PM10, PM20 and PM40 diets, respectively. Finally, the 10 and 20% fishmeal were substituted with combined silkworm pupae meal and promate meal®, refereed to as the SPM + PM10 and SPM + PM20 diets, respectively. Weight gain and specific growth rate of fish fed the MBM10 diet were higher than those of fish fed the Con, SPM20, PM20, PM40 and SPM + PM20 diets. Feed efficiency ratio of fish fed the SPM10, MBM10, MBM20, PM10 and SPM + PM10 diets was higher than that of fish fed the SPM + PM20 and PM40 diets. Protein efficiency ratio of fish fed the MBM10 and MBM20 diets was higher than that of fish fed the SPM20, PM20, PM40 and SPM + PM20 diets. In conclusion, dietary substitution of fishmeal with 10% SPM, 20% MBM, 10% PM and 10% SPM + PM could be made.

Effect of Dietary Composition with Different Feeding Regime on Compensatory Growth of Juvenile Olive Flounder Paralichthys olivaceus

Compensatory growth of juvenile olive flounder Paralichthys olivaceus fed different diets with different feeding regime was compared. Four hundred fifty fish (twenty five fish per tank) were randomly distributed into 18 of 180 L flow-through tanks. Six treatments were prepared: fish were hand-fed with the control (C) diet to satiation twice a day, six days a week, for 8 weeks (C-8W treatment); and other groups of fish were starved for 2 weeks and then fed with the C, high protein (HP), high carbohydrate (HC), high lipid (HL), and combined protein, carbohydrate and lipid (CPCL) diets to satiation twice a day, six days a week, for 6 weeks, referred to as C-6W, HP-6W, HC-6W, HL-6W, and CPCL-6W treatments, respectively. Final body weight of fish in HP-6W treatment was higher than that of fish in C-6W, but not different from that of fish in C-8W, HC-6W, HL-6W and CPCL-6W treatments. Specific growth rate of fish in HP-6W treatment was higher than that of fish in all other treatments except for fish in CPCL-6W treatment. Feeding rate of fish in C-8W treatment was higher than that of fish in HP-6W, HC-6W, HL-6W and CPCL-6W treatments, but not different from that of fish in C-6W treatment. In addition, feeding rate of fish in C-6W treatment was higher than that of fish in HP-6W, HL-6W and CPCL-6W treatments. Feed and protein efficiency ratios of fish in HP-6W, HC-6W, HL-6W and CPCL-6W treatments were higher than those of fish in C-6W treatment. None of moisture, crude protein and ash content of the whole body of fish excluding the liver was different among treatments. Dietary supplementation of protein, carbohydrate, lipid and their combination could improve compensatory growth of fish when fish were fed for 6 weeks after 2-week feed deprivation; especially, supplementation of dietary protein was the most effective to improve compensatory growth of fish.

Hypoxia-induced oxidative DNA damage links with higher level biological effects including specific growth rate in common carp, Cyprinus carpio L.

Both hypoxia and hyperoxia, albeit in different magnitude, are known stressors in the aquatic environment. Adopting an integrated approach, mirror carp (Cyprinus carpio L.), were exposed chronically (i.e. 30 days) to hypoxic (1.8 ± 1.1 mg O(2) l(-1)) and hyperoxic (12.3 ± 0.5 mg O(2) l(-1)) conditions and resultant biological responses or biomarkers were compared between these two treatments as well as with fish held under normoxic conditions (7.1 ± 1.04 mg O(2) l(-1)). The biomarkers determined included the activities of glutathione peroxidase (GPx), measurement of oxidative DNA damage (using modified Comet assay employing bacterial enzymes: Fpg and Endo-III), haematological parameters, histopathological and ultrastructural examination of liver and gills. Specific growth rate (SGR) of the fish, as an important ecotoxicological parameter was also determined over the exposure period. The study suggested that while the levels of hepatic GPx were unaffected, there was a significant difference in activity in the blood plasma under different exposure conditions; the hyperoxic group showed increased GPx activity by approximately 37% compared to normoxic group and the hypoxic group showed a decrease by approximately 38% than the normoxic group. Interestingly, oxidative DNA damage was significantly higher in both hypoxic and hyperoxic by approximately 25% compared to normoxic conditions, Fpg showing enhanced level of damage compared to the Endo-III treatment (P < 0.001). The haematological parameters showed enhanced values under hypoxic conditions. Transmission electron microscopic (TEM) studies revealed damage to liver and gill tissues for both the treatments. Interestingly, SGR of fish was significantly lowered in hypoxic by approx. 30% compared to normoxic condition and this was found to be correlated with DNA damage (R = -0.82; P = 0.02). Taken together, these results indicate that prolonged exposure to both hypoxic and hyperoxic conditions induce oxidative stress responses at both DNA and tissue levels, and hypoxia can result in compensatory changes in haematological and growth parameters which could influence Darwinian fitness of the biota with wider ecological implications.

Increasing dietary plant proteins affects growth performance and ammonia excretion but not digestibility and gut histology in turbot ( Psetta maxima) juveniles

A trial on turbot ( Psetta maxima) juveniles was undertaken to evaluate the effect of replacing dietary fishmeal (FM) with a complementary mixture of plant proteins (PP) consisting of soybean meal (SBM), wheat gluten meal (WGM) and corn gluten meal (CGM). Four practical diets were formulated to progressively replace 25% (PP25), 39% (PP39), 52% (PP52) and 66% (PP66) of FM protein. Forty animals per tank (initial weight 24.2 ± 4.4 g) were randomly distributed into twelve 450-liter square tanks connected to a closed recirculation system (temperature 18 ± 1 °C). The diets were tested in triplicate for 77 days. Final weight ranged from 126.6 g (PP25) to 99.5 g (PP66). Voluntary feed intake of group PP66 (55.5 g fish − 1 ) was significantly lower than in PP25. Specific growth rate in fish fed diet PP25 (2.14% day − 1 ) was significantly higher than those found both in PP52 (2.01% day − 1 ) and PP66 (1.82% day − 1 ) groups. Feed conversion ratio (FCR) in groups PP25 and PP39 (0.66–0.67) was lower in comparison with those of the other groups (FCR 0.70–0.74). None of the diets affected whole-body composition and hepatosomatic index. Condition factor significantly decreased with increasing dietary PP (2.06, 2.02, 1.97 and 1.91) whereas a significant increase in viscerosomatic index was observed in fish fed PP52 and PP66 (6.70–6.95) in comparison with the other two groups (6.31–6.21). Reduced protein retention was found in groups fed diet PP52 and PP66, with protein efficiency ratio (PER) ranging from 2.71 to 2.63 and gross protein efficiency (GPE) from 40.3 to 40.0, in comparison with the other two groups (PER 2.83 and GPE 45.5–45.8), even though apparent digestibility coefficients were not reduced. Ammonia excretion, (g total ammonia nitrogen 100 g protein intake − 1 ), was significantly higher for group PP25 (3.41) than group PP52 (2.61). Gut histology examined in four different sites of intestine (pyloric caeca, proximal, intermediate and distal intestine) revealed no noticeable differences among fish of the various diet groups. In conclusion, substitution of a mixture of SBM, WGM and CGM for up to 52% of FM protein did not reduce feed intake, and at 39% substitution, turbot maintained optimal growth rate and nutrient utilization. Worsened FCR of fish fed diets containing higher plant protein levels was not associated with a reduced digestibility of ingredients or alterations of gut histology.

Effect of ethanolic extract of propolis on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the effect of ethanolic extract of propolis (EEP) on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of EEP [0 (control), 1, 2, and 4 g kg(-1) diet] were fed to trout juveniles (mean weight 7.73 ± 0.17 g) for 10 weeks. Dietary EEP supplementation regardless of inclusion level significantly improved the specific growth rate of fish. Similarly, supplemental EEP generally improved the feed efficiency ratio and protein efficiency ratio, but no significant differences were observed between the 1 g kg(-1) EEP group and the control group. In addition, dietary EEP supplementation generally increased the plasma superoxide dismutase, lysozyme, total antioxidant capacity, glutathione peroxidase, and catalase activities, but decreased the plasma malondialdehyde level. The plasma triglycerides level was significantly lower in the 1 or 4 g kg(-1) EEP group as compared with the control group. Dietary EEP supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase activities, but increased the hepatic aspartate aminotransferase and alanine aminotransferase activities. These results indicate the potential to use the EEP as a growth promoter, hepatoprotective agent, and immunostimulant for rainbow trout.

Effect of partial replacement of dried, wet cull dates and date pits instead of yellow corn, supplemented with feed additives on growth performances of Nile tilapia (Oreochromis niloticus).

week feeding trials were conducted to evaluate the nutritive value of two forms of palm cull date and date pits as energy sources, supplemented with feed additives (Phytogenics), to be partially replaced (13.5%) yellow corn in feeding Nile tilapia fingerlings. Twelve experimental isonitrogenous (30.43% crude protein), isocaloric (436.43 kcal GE 100g-1) experimental diets were formulated taking into account energy sources and feed additives. Concerning energy source, four experimental diets were formulated which contain: yellow corn (YC) as control diet, dried cull date (DCD), wet cull date (WCD) and date pits (DP). As for feed additives (flavorings), three dietary sub-groups were built- up in each group to include: zero additives, 0.03 % Digestarom® (DG) and 0.03 % Marjoram leaf extract (MLE). Ten fingerlings (10.55 ± 0.30 g) were stocked/aquarium; two replicates per treatment and fed twice daily (six days) at 3% of body weight for 84 days. The results indicated that the partial replacement (13.5%) of WCD instead of YC supplemented with or without feed additives increased fish specific growth rate and feed utilization. However, replacement either DCD or DP decreased tilapia performances; meanwhile DP recorded the worst values. On the other hand, DG supplementation improved fish performances either fed WCD-based diets or control diets (YC). It could be concluded that wet cull date may be cost-effective when partially replaces yellow corn in tilapia diets as energy source, and improves fish performances when supplements with 0.03 % Digestarom®.

Evaluation of soybean meal in the formulated diets for juvenile Pangasianodon hypophthalmus (Sauvage, 1878)

The influence of soybean meal (SBM) on the growth and feed utilization of juvenile sutchi catfish (Pangasianodon hypophthalmus, Sauvage, 1878) was investigated. Eight isonitrogenous (300 g kg−1 CP) and isoenergetic (18 MJ kg−1) diets were formulated incorporating Argentine SBM to replace fish meal at 0, 150, 300, 450, 600, 750, 900 and 1000 g kg−1 dietary protein. Each diet was fed to three replicate groups of fish with an initial weight 6.0–6.2 g for twelve weeks. Growth performance decreased, and feed utilization was worsened with the increase in SBM inclusion in the diets. Final weight and relative growth rate (RGR) of fish fed control diet (0 SBM) were significantly higher than those fed test diets (P < 0.05). However, there were no significant differences in the final weight and RGR between the fish fed on 15 SBM, 30 SBM, 45 SBM and 60 SBM diets. Specific growth rate of fish fed 0 SBM, 15 SBM, 30 SBM and 45 SBM diets was significantly higher than those fed other diets. Feed conversion ratio of fish fed 0 SBM, 15 SBM, 30 SBM, 45 SBM and 60 SBM diets was significantly lower than those fed other diets (P < 0.05). The dry matter and protein digestibility were lesser in all the diets in comparison with the control diet. Hepatosomatic index and viscerosomatic index increased with increasing SBM in diet. This present trial indicated that fish meal can be replaced by SBM in the diet of juvenile sutchi catfish only up to 45% of fish meal protein without any adverse effect on growth, feed utilization and body composition.

Effect of Intermittent Feeding on Growth, Feed Utilization and Body Composition of Subadult Olive Flounder Paralichthys olivaceus in Suboptimal Temperature

The effect of intermittent feeding on growth, feed utilization and body composition of subadult olive flounder fed extruded pellet (EP) in suboptimal temperature () was determined. Two hundred twenty five subadult fish averaging 272 g were randomly distributed into fifteen of 300 L circular flow-through tanks (fifteen fish per tank). Five treatments with different days of feeding a week were prepared in triplicate: fish were hand-fed with EP to apparent satiation once a day, seven days a week (7DF), which was used as the control group or consecutive six, five, four and three days a week, for 12 weeks, referred to as 6DF, 5DF, 4DF and 3DF treatments, respectively. Weight gains and specific growth rates of fish in 6DF treatment were higher than those of fish in 7DF, 4DF and 3DF treatments, but not different from those of fish in 5DF treatment. Daily feed intake of fish in 6DF and 7DF treatments was higher than that of fish in 5DF, 4DF and 3DF treatments. Feed efficiency and protein efficiency ratio of fish were not different among treatments. There was no difference in the chemical composition of fish between treatments. Results of this study demonstrated that feeding five days per week could be recommended for subadult olive flounder fed extruded pellet in suboptimal temperature.

Effect of Dietary Protein and Lipid Levels on Compensatory Growth of Juvenile Olive Flounder (Paralichthys olivaceus) Reared in Suboptimal Temperature

Effect of dietary protein and lipid levels on compensatory growth of juvenile olive flounder (Paralichthys olivaceus) was determined in suboptimal temperature (). Five hundred forty fish averaging 79.2 g were randomly distributed into 27 of 300 L flow-through tanks (20 fish/tank). Nine treatments were prepared in triplicate: fish were hand-fed with control (C) diet for 10 weeks (10WF-C); four fish groups were starved for 1 week and then fed with C, high protein (HP), high lipid (HL) and combined high protein and high lipid (HPL) diets for 9 weeks, referred to as 9WF-C, 9WF-HP, 9WF-HL, 9WF-HPL, respectively; and other four fish groups were starved for 2 weeks and then fed with C, HP, HL and HPL diets for 8 weeks, referred to as 8WF-C, 8WF-HP, 8WF-HL and 8WF-HPL, respectively. Weight gain and specific growth rate of fish in 9WF-HP, 9WF-HPL, 8WF-HP and 8WF-HPL treatments were higher than those of fish in 9WF-HL and 8WF-HL treatments. Feed efficiency of fish in 8WF-HP treatment was higher than that of fish in 9WF-C, 9WF-HL and 8WF-HL treatments. Protein efficiency ratio of fish in 10WF-C, 8WF-C, 8WF-HP and 8WF-HPL treatments was higher that that of fish in 9WF-HL and 8WF-HL treatments. Juvenile olive flounder subjected to 2-week feed deprivation could achieve full compensatory growth with dietary supplementation of protein or combined high protein and high lipid.

Effects of Dietary Nutrient Composition on Compensatory Growth of Grower Olive Flounder Paralichthys olivaceus under Different Feeding Regimes at Suboptimal Temperature

The effects of dietary nutrient composition on compensatory growth of grower olive flounder (Paralichthys olivaceus) under different feeding regimes at suboptimal temperature were determined. Four hundred five fish weighing 271.2 g were distributed into 27 300 L flow-through tanks (15 fish per tank). Nine treatments were prepared in triplicate: fish were hand-fed with control (C) diet for 12 weeks (12WF-C); four groups of fish were starved for 1 week and then fed C, high-protein (HP), high-lipid (HL), or combined high-protein and high-lipid (HPL) diets for 11 weeks; these groups are referred to as 11WF-C, 11WF-HP, 11WF-HL, and 11WF-HPL, respectively. Four other groups of fish were starved for 2 weeks and then fed C, HP, HL, and HPL diets for 10 weeks; these groups are referred to as 10WF-C, 10WF-HP, 10WF-HL, and 10WF-HPL, respectively. Weight gain and specific growth rate of fish from 12WF-C group were greater than those of fish from 11WF-C, 11WF-HP, 11WF-HL, 10WF-C, 10WFHP, and 10WF-HL groups, but not different from those of fish from 11WF-HPL and 10WF-HPL groups. Feed-efficiency ratio of fish from 12WF-C, 11WF-HP, 11WF-HPL, 10WF-HL, and 10WF-HPL groups was higher than that of fish in 11WF-C, 11WF-HL, 10WF-C, and 10WF-HP groups. The results of this study demonstrated that grower olive flounder subjected to 1- or 2-week feed deprivation were able to achieve full compensatory growth at suboptimal temperature only when fed HPL diet.

Effect of dietary lipid levels on growth, feed utilization, body composition and serum metabolites of meagre ( Argyrosomus regius) juveniles

The study investigates the effect of dietary lipids on growth of meagre ( Argyrosomus regius) juveniles. Triplicate groups of fish (average weight ± SD, 229.7 ± 1.4 g) were fed for 110 days three isonitrogenous experimental diets (43% crude protein, dry matter) containing 13, 17, or 21% crude lipids. Body weight, total length and specific growth rate of fish fed the 17% lipid diet were significantly higher than that of fish fed the 13 and 21% lipid diets. Daily feed intake was not affected by the dietary lipid level, but there were significant differences in feed conversion ratio and protein efficiency ratio. There was no significant difference in condition factor, hepatosomatic or viscerosomatic indexes. Proximate analysis indicated that the lipid content of whole body and muscle was affected by the diets, whereas the other chemical components of whole body, muscle and liver were unaffected by the increase in dietary lipid content. Whole body and muscle of fish fed the 21% lipid diet showed significantly higher values of total lipids (whole body: 7.41 ± 0.45% and muscle: 0.64 ± 0.13%) than fish fed 17 and 13% lipid (whole body: 5.92 ± 0.12%, muscle: 0.37 ± 0.08% and whole body: 5.76 ± 0.23%, muscle: 0.31 ± 0.02%, respectively). Serum metabolites did not show significant differences among the three dietary lipid levels. Overall, the results indicated that the best growth performance was observed in fish fed the 17% lipid diet, whereas the increase of dietary lipid level from 17% to 21% had a negative effect on growth. In conclusion, meagre juveniles appear to have similar lipid requirements with other Mediterranean species and excess dietary lipid level should be avoided, since the increase from 17% to 21% resulted in higher fat accretion and impaired growth performance.

배합사료 공급율 및 공급횟수가 겨울철에 사육된 육성기 넙치의 성장 및 체조성에 미치는 영향

Two 15-week feeding trials were conducted to investigate how the rate and frequency of feeding affected the winter growth of olive flounder (<TEX>$13^{\circ}C$</TEX>). In the first experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.0$</TEX> g) were fed extruded pellets twice a day at feeding rates of 0.1, 0.25, 0.4, 0.55, and 0.57% (satiation) body weight per day (BW/d). The weight gain, specific growth rate, and feed efficiency increased significantly (P<0.05) with the feeding rates from 0.1 to 0.55% BW/d, but no significant differences in these parameters were found for fish fed diets of 0.55% BW/d and satiation. The moisture and ash contents of whole body of fish tended to decrease as the feeding rate increased, but the opposite trend was found for crude lipid content. In the second experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.3$</TEX> g) were fed extruded pellets to apparent satiation at the three different feeding frequencies: one meal 2 days, one meal a day and two meals a day. The weight gain and specific growth rate of fish fed one meal 2 days were significantly (P<0.05) lower than those of fish fed one or two meals a day, whereas no significant differences in the weight gain and specific growth rate were found between fish fed one and those fed two meals a day. Feed efficiency and condition factor were not significantly affected by feeding frequency. Based on these results, a feeding rate of 0.3% BW/d is recommended as maintenance feeding level, and the optimum feeding frequency is one meal a day with satiation feeding for the growth of olive flounder (117-147 g) during winter (<TEX>$13^{\circ}C$</TEX>).

Effects of 11-ketotestosterone and fishmeal in the feed on growth of juvenile tilapia ( Oreochromis mossambicus)

The effects of 11-ketotestosterone (11KT) and dietary fishmeal on growth of tilapia ( Oreochromis mossambicus) were examined. Juvenile tilapia, weighing about 8 g, were reared for 50 days with isonitrogenous and isocaloric diets containing fishmeal or all plant proteins, each with or without supplementation of 11KT. Fish fed fishmeal-based (FM) diets grew significantly faster than those fed soybean meal-based (SM) diets. Addition of 11KT (10 mg/kg) to the FM diet significantly augmented growth, whereas no significant effect of 11KT was observed in fish fed SM diet. In accord with the accelerated growth, specific growth rates of fish fed FM diets were significantly greater than those of fish fed SM diets, although addition of 11KT to FM or SM diet had no effect on this parameter. Males showed significantly higher plasma levels of insulin-like growth factor-I (IGF-I) than did females; however, there was no consistent effect of fishmeal or 11KT on plasma IGF-I levels within each sex. Plasma levels of 11KT were significantly higher in males than in females. In males, plasma 11KT levels were significantly higher in fish fed FM diets than in those fed SM diet. No significant effect of fishmeal or 11KT was observed on plasma levels of 11KT or 17β-estradiol (E 2) in females. Low but significant levels of vitellogenin (Vg) were found in male plasma. Plasma Vg levels were significantly lower in fish fed SM diets than in fish fed FM diets in both males and females. These results indicate that addition of 11KT to the fishmeal-based diet stimulated growth, minimally affecting plasma levels of IGF-I, 11KT, E 2 and Vg. The absence of effect of 11KT in fish fed the soybean meal-based diet may indicate that the estrogenic activities or some components in the SM diet are likely to interfere with the growth-promoting effects of 11KT.

The influence of water temperature and ration on the growth, body composition and energy budget of tongue sole ( Cynoglossus semilaevis)

The influence of water temperatures (16, 22 and 28 °C) and ration levels (0%, 25%, 50%, 75% and 100% of satiation) on the growth, body composition and energy budget in juvenile tongue sole ( Cynoglossus semilaevis) was investigated over 60 days. The specific growth rates of fish increased with increasing ration levels. Fish fed to 100% satiation at 22 °C exhibited better growth than other treatments. The relationship among SGR w, SGR e, temperature ( T) and ration (RL w, in weight and RL e, in energy) could be described by the regression equations: SGR w = 20.778 log(RL w + 5) − 0.0767 T − 13.628, SGR e = 11.016 log(RL e + 5) − 0.152 T − 6.730. The maintenance ration levels were 0.19%, 0.46% and 0.74% of body weight, while 1.79%, 3.21% and 4.94% of body energy at 16, 22 and 28 °C, respectively. Ration level from 50% to 100% satiation did not influence food conversion efficiency. There is no significant difference in apparent digestion rate between fish fed to 75% and 100% satiation. The content of lipid in fish tended to increase with increasing ration levels, while tended to decrease with increasing water temperature. The crude protein content in fish tended to decrease with increasing ration levels at low temperature (16 °C), while tended to increase at high temperature (22 and 28 °C). The proportion of food energy assimilated in growth and the proportion consumed for respiration dominated the mode of the energy allocation of juvenile tongue sole. In the temperature range of this experiment, the proportion of food energy allocated to growth decreased with increasing temperature, and was not affected significantly by ration level from 50% to 100% satiation at the same temperature. The proportion of food energy consumed for respiration decreased with increasing ration, while increased with increasing temperature. The maximum specific growth rate occurred in fish fed to satiation at 22 °C, which suggested that commercial farmers could feed juvenile tongue sole to satiation at 22 °C to obtain higher growth rate.

Effect of dietary lipid level on the growth performance, feed utilization, body composition and blood chemistry of juvenile starry flounder (Platichthys stellatus)

A study was conducted to determine the effect of dietary lipid level on the growth performance, feed utilization, body composition and blood chemistry of juvenile starry flounder. Five isonitrogenous diets with increasing dietary lipid levels (6%, 10%, 14%, 18% and 22% dry material) were each fed to triplicate groups of starry flounder (29.9 g) for 8 weeks. Weight gain (WG) and specific growth rate of fish fed the 6% lipid diet were significantly lower than the other groups, while there was no significant difference in fish fed the 10%, 14%, 18% and 22% lipid diets. Body lipid content increased with increasing dietary lipid levels. The moisture content of the whole body was negatively correlated to the dietary lipid level. The dietary lipid level also affected the lipid content of the dorsal muscle positively. Liver lipid content increased as the dietary lipid level increased from 6% to 14% and then decreased. With increasing dietary lipid level, the nitrogen retention achieved the highest value when the fish were fed the 14% lipid diet, but there were no significant differences with the 10% and 22% groups. The plasma total protein content first showed an increasing and then a decreasing trend with increasing dietary lipid level, and it was significantly higher in the 14% lipid group than other groups. Based on the WG response using the broken-line model, the optimum dietary lipid level for juvenile starry flounder was estimated to be 10.62% in the experiment.

Interactive effects of dietary cholesterol and protein sources on growth performance and cholesterol metabolism of Japanese flounder (Paralichthys olivaceus)

A feeding trial was conducted to compare the effects of supplemental cholesterol in fish meal (FM), fish protein concentrate (FPC), soy protein isolate (SPI) and soy protein concentrate (SPC)-based diets on growth performance and plasma lipoprotein levels of Japanese flounder (Paralichthys olivaceus). Eight isonitrogenous and isocaloric diets including FM, FPC, SPI or SPC as sole protein source with or without supplementation with 10 g cholesterol kg⁻¹ diet were fed to juvenile fish for 8 weeks. Dietary cholesterol supplementation significantly increased the feed intake and specific growth rate in fish fed SPI-based diets, but decreased those in fish fed FPC-based diets. In addition, cholesterol supplementation significantly increased the level of cholesterol and ratio of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol in plasma of fish fed fish protein-based diets, whereas no effects were observed in fish fed soy protein-based diets. The hepatic lipid content of fish fed FPC-, SPI- or SPC-based diets were significantly increased by supplemental cholesterol, but no influence was observed in fish fed FM-based diets. These results suggested that dietary protein source modify the growth-stimulating action of cholesterol; cholesterol supplementation may increase the arteriosclerotic lesion in fish fed fish protein-based diets and the incidence of fatty liver in fish fed soy protein-based diets.