Compensatory growth response of Sparus aurata following different starvation and refeeding protocols

A feeding trial evaluated the influences of different cycles of starvation and refeeding protocols for 7 weeks on growth and feed intake in 14‐g gilthead sea bream, Sparus aurata. Following 7 weeks of alternated cycles, all the groups were fed to apparent satiation for a further 3 weeks. Three groups of fish were fasted for 2, 4 or 7 days (S2, S4 and S7, respectively) and then refed until their relative feed intake differed by less than 20% of fed controls until the end of the week 7, while a fourth group (S7/Rf14) experienced three cycles, each consisting of 1 week of food deprivation followed by 2 weeks of satiation feeding. Control (C) fish were fed to satiation throughout the trial. The fish were fed a sea bream diet (450 g kg^?1 crude protein) according to the protocols, twice a day for 7 weeks. Growth performance and feed intake in continuously fed control group were significantly higher than those of the deprived groups (S2, S4, S7 and S7/Rf14) (P < 0.05). Weight gain highly correlated with total feed intake (R² = 94), and feed efficiency was the highest in the control group than other deprived groups (P < 0.05). The juveniles of gilthead sea bream demonstrated only a partial compensation during the cycling period and even after being fed to satiation for another 3 weeks. The convergence of growth trajectories and subsequent hyperphagic responses of the groups fed according to protocols are discussed in terms of possible costs of compensatory growth.     

Compensatory Growth of Juvenile Flounder Paralichthys olivaceus L. and Changes in Biochemical Composition and Body Condition Indices during Starvation and after Refeeding in Winter Season

Compensatory growth and changes in biochemical composition, hematocrit and body condition indices of juvenile flounder Paralichthys olivaceus were assessed during starvation and after refeeding. Twenty juvenile fish were stocked into each 200‐L flow‐through tank to give five treatments with three replicates per treatment: control group fish (C) were hand fed to apparent satiation twice daily for 8 wk, whereas the Sl, S2, S3, and S4 fish were hand fed to apparent satiation twice daily for 7, 6, 5, and 4 wk after 1, 2, 3, and 4 wk of starvation, respectively. During starvation, weight decreased linearly with periods of feed deprivation up to 3 wk. Survival was not significantly different among treatments. At the end of the feeding trial, weight gain (g/fish) and specific growth rate (SGR) of flounder in S2 was significantly (P < 0.05) higher than those of fish in S3 or S4, but not significantly different from those of fish in C or Sl. Feed consumption of flounder (g/fish) was proportional to duration of feeding except for that of fish in S2. Feed efficiency ratio (FER) and protein efficiency ratio (PER) values for flounder in S2 were significantly (P < 0.05) higher than those for fish in C, but not significantly different from those for fish in Sl, S3, or S4. During starvation, hepatosomatic index (HSI) and lipid content of flounder without liver decreased with periods of feed deprivation. However, HSI and condition factor (CF) for flounder in S2 were significantly (P < 0.05) higher than those for fish in Sl, S3, S4 and C except for CF in Sl at the end of the feeding trial. Proximate composition of flounder without the liver was not significantly different among treatments at the end of the feeding trial. In considering above results, juvenile flounder achieved compensatory growth with up to 2‐wk feed deprivation. Compensatory growth of flounder fed for 6 wk after 2‐wk feed deprivation was well supported by improvement in SGR, FER, and PER. HSI could be a good index to monitor changes in body condition during starvation and after refeeding.     

Compensatory Growth of Pond-reared Hybrid Striped Bass, Morone chrysops × Morone saxatilis, Fingerlings

Compensatory growth (CG) or “catch‐up growth” is a period of super‐accelerated growth following a period of suboptimal conditions (i.e., lack of prey availability or overwintering). Little is known about the CG response in pond‐raised fish and whether hybrid striped bass (HSB), Morone chrysops × Morone saxatilis, might exhibit the rapid growth states or improvements in other production characteristics that may accompany the response. To evaluate the potential for CG in HSB culture, a 16‐wk growth trial in twelve 0.1‐ha earthen ponds was conducted. Approximately 2850 fish (mean weight ± SD = 3.2 g ± 1.1) were stocked into ponds and subjected to one of four cyclic feeding regimens. Treatment regimens included a control (0 wk, fed twice daily to apparent satiation) and cycles of 1, 2, or 4 wk of feed deprivation, followed by 1, 2, or 4 wk of feeding to apparent satiation. Fish in the 4‐wk feeding regimen were offered feed twice during the feed‐deprivation period (once every other week). Growth, specific growth rate (SGR), hepatosomatic index (HSI), intraperitoneal fat ratio, and condition factor (CF) were measured every other week, while overall growth, feed efficiency (FE) (FE = [weight gain/feed fed] × 100), and survival were calculated at the trial termination. The effect of these feeding regimens on water quality was examined by monitoring pH, turbidity, total ammonia nitrogen, nitrite–nitrogen, nitrate–nitrogen, soluble reactive phosphorus, and chlorophyll a weekly; total nitrogen and phosphorous biweekly; and dissolved oxygen and temperature twice daily. Cyclic feeding elicited CG; fish subjected to the 2‐wk regimen had a significantly higher SGR than 0‐wk controls during all but the final refeeding period. FE was higher for all fish in the cyclic regimens, although only FE for fish in the 2‐wk regimen was statistically greater (40%) than the controls. HSI was the most responsive measure and significantly decreased in the 2‐ and 4‐wk treatments during feed‐deprivation period and overcompensated during the refeeding period. CF also varied with feeding cycle and proved to be an effective nonlethal measure of predicting a CG response. No statistical differences in water quality parameters were observed. These data suggest that CG can be effectively induced in pond‐raised HSB and that the increase in FE warrants further research for practical application. Future pond studies with fingerling HSB fish should be conducted with emphasis on feed‐deprivation periods of 2 wk and refeeding periods of at least twice that of the feed‐deprivation period.     

Assessment of Compensatory Growth in Channel Catfish Ictalurus punctatus R. and Associated Changes in Body Condition indices

A feeding trial was undertaken to evaluate compensatory growth in channel catfish and to chronicle the changes in body condition associated with the imposed feeding strategy. Four 1200-L circular tanks were each stocked with approximately 600 fingerling channel catfish (mean initial weight 32 g). Two tanks represented control fish which were fed to apparent satiation once daily throughout the trial. The two remaining tanks of fish were unfed for 4 wk and subsequently refed daily to apparent satiation for the following 10 wk in order to elicit a compensatory growth response. Fish fed to apparent satiation during the first 4 wk of the trial had a 41% increase in body weight, while the fasted fish decreased in weight by 20%. During the subsequent refeeding period, previously unfed fish were not able to increase growth rates sufficiently to overcome weight loss imposed by the 4-wk feed restriction. However, after 8 wk of refeeding, total increase in body weight of the previously unfed fish was 179 % of initial weight and similar to that of control fish which gained 231 % of initial weight. Hepatosomatic index (HSI) and condition factor decreased rapidly during the fasting period and increased rapidly to control levels during subsequent refeeding. The intraperitoneal fat (1PF) ratio and muscle ratio responded more slowly to feed restriction with IPF ratio decreasing consistently after 2 wk feed restriction. Muscle ratio showed little effect from the 4-wk period of feed deprivation. It appears that not feeding channel catfish fingerlings for 4 wk is too long to induce a compensatory growth response that is optimal for aquaculture; however, HSI may be the index of choice for detecting when refeeding should begin to maximize compensatory growth.     

Compensatory Growth of Juvenile Olive Flounder, Paralichthys olivaceus L., and Changes in Proximate Composition and Body Condition Indexes during Fasting and after Refeeding in Summer Season

Compensatory growth of juvenile olive flounder, Paralichthys olivaceus L., and changes in proximate composition and body condition indexes of fish during fasting and after refeeding were investigated during the summer season. Groups of 25 fish each (initial body weight of 16 g) were randomly distributed into fifteen 180‐L flow‐through tanks. Fish were fed the experimental diet containing crude protein 46.9% and crude lipid 8.0% with estimated energy level of 14.6 kJ/g diet for 6 d/wk. Five treatments in triplicate were prepared for this study: C, S1, S2, S3, and S4. Fish in the control group (C) were hand‐fed to apparent satiation twice daily. Fish in treatments S1, S2, S3, and S4 experienced 1, 2, 3, and 4 wk of starvation and were then hand‐fed to apparent satiation twice daily during the remaining 7, 6, 5, and 4 wk of the experiment, respectively. A group of starved fish in the similar size was stocked and fasted throughout the 8‐wk feeding trial for chemical and blood analysis. The feeding trial lasted for 8 wk. Weight of fish linearly decreased with week of starvation (P < 0.0001). Linear relationship between condition factor (CF) and hepatosomatic index (HSI) against week of starvation was observed in the starved group of fish. Survival was not significantly (P > 0.05) affected by feeding strategy. However, weight gain and specific growth rate (SGR) of olive flounder in C, S1, and S2 were significantly (P < 0.05) higher than those of fish in S3 and S4. The poorest weight gain and specific growth rate (SGR) were obtained in fish of S4. Feed consumption of olive flounder in C, S1, and S2 was significantly (P < 0.05) higher than that of fish in S3 and S4. Feed efficiency, protein efficiency ratio, and protein retention of olive flounder in C and S1 were not significantly (P > 0.05) different from those of fish in S2 but significantly (P < 0.05) higher than those of fish in S3 and S4. Hematocrit, CF, and HSI of olive flounder were not significantly (P > 0.05) affected by feeding strategy. Chemical composition of fish was not significantly (P > 0.05) affected by feeding strategy. In considering these results, it can be concluded that juvenile olive flounder have the ability to fully compensate for 2‐wk feed deprivation during the summer season. Besides, feed efficiency in fish fed for 7 and 6 wk after 1‐ and 2‐wk feed deprivation was comparable to that in fish fed for 8 wk.     

Somatic and physiological responses to cyclic fasting and re‐feeding periods in sobaity sea bream (Sparidentex hasta,Valenciennes 1830)

Different fasting and re‐feeding cycles were tested in a 60‐day trial in sobaity sea bream (Sparidentex hasta) juveniles to evaluate their effects on growth, physiological and biochemical parameters. Fish were exposed in triplicate to the following feeding regimes: control (fed everyday); F‐RF₁₊₁ (1 day of starvation followed by 1 day of re‐feeding); F‐RF₂₊₂ (2 days of starvation followed by 2 days of re‐feeding); F‐RF₃₊₃ (3 days of starvation followed by 3 days of re‐feeding); F‐RF₆₊₆ (6 days of starvation followed by 6 days of re‐feeding); and F‐RF₁₊₂ (1 day of starvation followed by 2 days of re‐feeding). A reduction in body mass between 10.0% (F‐RF₁₊₁) and 24.3% (F‐RF₆₊₆) was found in comparison with the control group after 60 days. As the length of fasting increased, the compensation coefficients in feed intake and weight gain decreased. Body lipid content decreased as fasting cycles increased. Haemoglobin, plasma protein, lysozyme and alkaline phosphatase activities were the most reliable biomarkers for assessing the nutritional condition in sobaity sea bream. A feeding strategy based on 1 day of starvation followed by 2 days of re‐feeding (F‐RF₁₊₂ group) may be advisable for on‐growing sobaity sea bream without reduction in growth and alteration of their haematological and physiological parameters.     

Compensatory growth of juvenile black sea bream,Acanthopagrus schlegelii with cyclical feed deprivation and refeeding

An 8‐week feeding trial was conducted to evaluate compensatory growth of juvenile black sea bream, Acanthopagrus schlegelii (initial weight 9.56 ± 0.12 g) in fifteen 300 L indoors flow‐through circular fibreglass tanks. Feeding regimes was designed as follows: the control group (fed continuously), and S1, S2, S3 and S4 groups experienced 1, 2, 3 and 4 days of feed deprivation and then refeeding for the remaining days per week respectively. Changes in body weight, specific growth rate (SGR), feed intake (FI) and feed efficiency ratio (FER) were examined biweekly during the trial. At the end of the cyclical feeding periods, survival was not significantly affected by feeding strategy (P > 0.05). Final body weight of fish in S1 group was significantly higher than the control group (P < 0.05) after an 8 weeks trial, and fish in the S2 group reached the same body weight of the control fish (P > 0.05), however, the growth data in the S3 and S4 groups could not catch‐up with the control treatment (P < 0.05). In the first 4 weeks, SGR values of fish with feed deprivation more than 2 days per week were inferior to those of control group (P < 0.05); however, no significant differences of SGR were observed among the groups for the last 4 weeks (P > 0.05). FI increased significantly with the starvation days increasing during the whole feeding trial (P < 0.05). At the periods 2, 4 and 6 weeks, FER values increased significantly with increasing feed‐deprivation days up to S2 group and then levelled off (P < 0.05); however, FER in S2 group was only higher than that in S0 and S1, but no significant differences were found among the other treatments at the end of week 8. Significant differences were found in apparent digestibility coefficients (ADCs) of dry matter and crude protein among the treatments, while ADCs of crude lipid were unaffected. Protein and lipid contents in whole body and dorsal muscle showed declining tendency with increasing food deprivation days, while moisture contents tended to increase (P < 0.05). Serum parameters were markedly affected by feeding regimes except for total protein concentration and thyroxine level. The present results indicated that starvation for 1 and 2 days per week of juvenile black sea bream could achieve over‐compensation and complete compensation respectively. However, in case of longer term feed restriction regime, fish failed to obtain good growth performance.     

Cyclical feed deprivation and refeeding fails to enhance compensatory growth in Nile tilapia, Oreochromis niloticus L.

A 12-week experiment was carried out to evaluate compensatory growth of 6.6 g Nile tilapia Oreochromis niloticus L. under three cyclical regimes of feed deprivation and refeeding. The deprivation and refeeding regimes included four cycles of 1 week of deprivation and 2 weeks of refeeding (S1F2), two cycles of 2 weeks of deprivation and 4 weeks of refeeding (S2F4) and one cycle of 4 weeks of deprivation and 8 weeks of refeeding (S4F8). A group of fish fed to satiation twice daily throughout the experiment served as control. At the end of the refeeding periods, fish deprived and refed cyclically had higher feed intake and specific growth rates (SGR), but lower body weight, than that of the control fish. There was no significant difference in feed efficiency ratio (FER) between the control and fish subjected to feed deprivation during the refeeding periods, and nitrogen retention efficiency (NRE) was not different between any two treatments throughout the experiment. At the end of the experiment, fish subjected to feed deprivation had lower body weight but similar body composition, relative to those of the control fish. No significant differences were found in final body weight, NRE and body composition between the fish subjected to different cycles of deprivation and refeeding, but the fish subjected to one cycle of deprivation and refeeding exhibited high mortality. Our results indicate that partial growth compensation induced by various cycles of feed deprivation and refeeding does not confer a huge advantage in terms of enhancing the production efficiency and reducing the nitrogen waste output in Nile tilapia farming 29–30 °C.     

Compensatory Growth of Olive Flounder,Paralichthys olivaceus,Fed the Extruded Pellet with Different Feeding Regimes

This study was performed to determine compensatory growth of juvenile olive flounder fed the extruded pellet (EP) with different feeding regimes. Seven treatments with triplicates of different feeding regimes were prepared; α fish was daily fed for 6 d a week throughout 8 wk (8WF); α fish was starved for 1 wk and then fed for 3 wk twice [(1WS + 3WF) × 2]; β fish was starved for 2 wk and then fed for 6 wk (2WS + 6WF); χ fish was starved for 5 d and then fed for 9 d four times [(5DS + 9DF) × 4]; δ fish was starved for 10 d and then fed for 18 d twice [(10DS + 18DF) × 2]; δ fish was starved for 2 d, fed for 5 d, starved for 3 d, and then fed for 4 d four times [(2DS + 5DF + 3DS + 4DF) × 4]; and φ fish was starved for 4 d, fed for 10 d, starved for 6 d, and then fed for 8 d twice [(4DS + 10DF + 6DS + 8DF) × 2], respectively. Total feeding day was all same, 36 d except for control group (48 d). Weight gain of flounder in the 8WF treatment was higher than that of fish in other treatments. And weight gain of flounder in the 2WS + 6WF treatment was higher than that of fish in the (5DS + 9DF) × 4 and (4DS + 10DF + 6DS + 8DF) × 2 treatments. Feed consumption of flounder in the 8WF treatment was higher than that of fish experienced feed deprivation. Feed efficiency ratio (FER), protein efficiency ratio (PER), and protein retention (PR) were not significantly different among treatments. Chemical composition of the whole body of fish with and without liver, except for moisture content of liver, was not different among treatments. T₃ level of fish in the 8WF and 2WS + 6WF treatments was higher than that of fish in the (5DS + 9DF) × 4 treatment. It can be concluded that juvenile olive flounder achieved better compensatory growth at 6‐wk refeeding after 2‐wk feed deprivation compared with that of fish with different feeding regimes. And T₃ level of fish seemed to partially play an important role in achieving compensatory growth.     

Compensatory Growth in Juvenile Freshwater Turtles,Chinemys reevesii,Following Feed Deprivation

The compensatory growth response of juvenile three‐keeled pond turtles, Chinemys reevesii, was investigated by food deprivation for 1–4 wk and then refeeding for 4 wk. After feeding resumed, only turtles that were deprived over 2 wk displayed higher specific growth rates than the continuously fed turtles for 1 wk, but their weights were lower than the control at the end of refeeding, showing a partial compensatory growth pattern. Their feeding rate, rather than the feed conversion efficiency and apparent digestibility of energy, was higher than the control during the compensatory phase, indicating that hyperphagia was responsible for the compensatory growth. As starvation intensified, protein concentrations of deprived turtles increased significantly, whereas the contents of fat tissues decreased sharply. After 4 wk of refeeding, the contents of fat tissues in deprived turtles returned to the control level, whereas protein concentrations did not, indicating that lipid rather than protein was the main fuel utilized during short‐term starvation for juvenile turtles aged over 2 mo.     

Fasting and refeeding lead to more efficient growth in lean pacu (Piaractus mesopotamicus)

We evaluated whether body fat content affects the energetic metabolism and growth in pacu submitted to daily feeding, fasting and refeeding. For 15 days, fish were fed different diets to obtain lean and fat conditions, and then subjected, for 20 days to: (1) continuously feeding (control), or (2) fasting for 15 days and refeeding for 5 days. Blood (glucose, triglycerides, cholesterol, non‐esterified fatty acids and total protein) and tissue (liver lipid and glycogen, muscle lipid and mesenteric fat) metabolic indicators, and growth performance parameters (weight gain, specific growth rate, daily feed intake and feed conversion ratio) were measured. Fasting led both lean and fat pacu to make notable use of their energy reserves, through glycogenolysis and lipolysis, reflected in reduced blood glucose and triglycerides, liver glycogen and muscle lipid levels. Lipolysis was confirmed by the high levels of non‐esterified fatty acids, especially in fat pacu. Refeeding led to higher plasma glucose and liver lipid in lean fish. Muscle fat increased in fat fish but was not restored in lean fish, while mesenteric fat index (MFI) remained the same in fat fish and increased in lean fish. Although refeeding occurred only for 5 days, lean fish grew more and were more efficient at utilizing food (higher weight gain and better feed conversion ratio). In conclusion, our results suggest that fat pacu have higher glycogenic and lipogenic abilities, and the higher deposition of lipids in fish does not mean higher availability of energy for growth when compensatory growth is stimulated by refeeding after fasting.     

Effects of natural feeding stimulants and glutamic acid supplementation on the feed intake,growth performance and digestive enzyme activities of red sea bream (Pagrus major) fed fish meal‐free soy protein concentrate (SPC)‐based diet

Two experiments were conducted for red sea bream (Pagrus major). In experiment 1, the optimum level of glutamic acid and natural feeding stimulants to enhance feed intake were determined and found that glutamic acid level of 0.5% and fish meat hydrolysate (FMH) were effective. In experiment 2, fish were fed with soy protein concentrate (SPC)‐based diet with synthetic feeding stimulants (Basal diet), the Basal diet with FMH (FMH diet), the FMH diet with glutamic acid (FMHG diet) and with fish meal diet (FM diet) as a control until satiation for 8 weeks. Feed intake of FMHG‐fed fish was significantly higher than others (p < 0.05). Specific growth rate and the feed conversion ratio of FMHG were comparable to those of FM‐fed fish (p > 0.05). Relative visceral fat ratio and crude lipid content of any SPC‐based diet‐fed fish tended to be lower than those of FM diet‐fed fish. There were no significant differences in trypsin and lipase activities hepatopancreas among treatments. SPC can be utilized as a sole protein source in a diet for red sea bream. The lower growth performance in SPC‐based diet‐ fed fish was not due to poor digestive enzyme secretion but could be associated with lipid utilization disorder.     

Effects of Periodic Feed Deprivation on Growth, Feed Efficiency, Processing Yield, and Body Composition of Channel Catfish Ictalurus punctatus

Two studies were conducted in 110‐L flow‐through aquaria and 0.4‐ha ponds to evaluate effects of periodic feed deprivation on the growth performance of channel catfish Ictalurus punctatus. Fish were deprived of feed 0, 1, 2, or 3 consecutive d/wk, l d per 5‐d period, or 3 consecutive d per 10‐d period and fed to satiation on days fish were fed. In Experiment 1, fish fed less frequently than daily consumed significantly less feed (over the experimental period) and gained significantly less weight than fish fed daily, except that feed consumption of fish deprived of feed 1 d/wk was not significantly different from that of fish fed daily. Compared with fish fed daily, fish deprived of feed 2 d/wk had significantly lower feed conversion ratio (FCR). Visceral fat of fish deprived of feed 1 or 2 d/wk was similar to that of fish fed daily, but fish deprived of feed for longer periods had significantly lower visceral fat than fish fed daily. Regression analysis indicated that feed consumption, weight gain, and visceral fat increased linearly as the number of days that fish were fed increased. In Experiment 2, there were no significant differences in the amount of feed fed between fish deprived of feed 1 d/wk and those fed daily. Net production of fish deprived of feed 1 or 2 d/wk or 1 d per 5‐d period was not significantly different from that of fish fed daily, but fish deprived of feed for longer periods had significantly lower net production than fish fed daily. Visceral fat of fish deprived of feed 1 d/wk or 1 d per 5‐d period was similar to that of fish fed daily, but fish on other treatments had significantly lower visceral fat than fish fed daily. Regression analysis showed that as the number of days fed increased the amount of feed fed and net production increased quadratically. Feed conversion ratio, carcass yield, visceral fat, and fillet fat increased, while fillet moisture decreased linearly as the number of days fed increased. Although feeding less frequently than daily may improve feed efficiency, and fish deprived of feed may demonstrate compensatory growth when a full feeding regime is resumed, it may be difficult to provide enough feed to satiate all size‐classes of fish under a multiple‐batch cropping system without causing water quality problems. Under normal economic conditions, fish should be fed daily to apparent satiation without waste and without causing water quality problems. However, during periods of unfavorable economic conditions, channel catfish raised from advanced fingerlings to market size may be fed less frequently than daily to reduce production cost. Results from the present study indicated that feeding channel catfish to satiation 5 or 6 d/wk (not feeding on one or two weekend days) could provide some benefits in reducing production cost through reduced feed and labor costs for food‐sized channel catfish during periods of low fish prices and high feed prices.     

Physiological Response to Dolops carvalhoi (Crustacea: Branchiura) Infection by Pacu,Piaractus mesopotamicus,Subjected to Short Cycles of Food Restriction and Refeeding

Feeding strategies that reduce feed and promote compensatory growth could be an interesting tool to reduce costs in the fish production. However, fish health must be monitored to evaluate if their physiological response to adverse conditions, such as parasite infection, does not become compromised. A 12‐wk growth trial was conducted to determine the physiological responses of pacu, Piaractus mesopotamicus, that were subjected to different fasting/refeeding cycles and infected with the Dolops carvalhoi. The schemes were: (i) control group fish (FD), (ii) food‐restricted and controlled refeeding group (FR/Rc), and (iii) food‐restricted and refeeding to satiation group (FR/Rs). After 84 d, the fish were exposed to D. carvalhoi for 30 h. The fish subjected to food restriction did not exhibit compensatory growth. Cortisol levels decreased in all groups within 30 h after infection. Glucose levels increased 6 h after the D. carvalhoi in the FR/Rs and 30 h after infection in the FD. In all of the fish groups, the hematocrit values were reduced after infection, and it was associated with a reduction in the mean corpuscular volume and erythrocytes. At 30 h after infection, the number of erythroblasts increased. The use of the feeding schemes does not indicate a failure of the pacu physiological responses.     

Dietary supplementation with Mannanoligosaccharides (MOS) from Bio‐Mos enhances growth parameters and digestive capacity of gilthead sea bream (Sparus aurata)

Dietary mannanoligosaccharide (MOS) from commercial product, Bio‐Mos supplementation, has been examined for its effects on weight gain and feed conversion of domestic mammals and birds, but very few studies have evaluated the responses of aquacultural species to MOS. A feeding and digestibility trial was performed to asses the potential beneficial effect of two levels of Bio‐Mos on growth, feed utilization, survival rate and nutrients’ digestion of gilthead sea bream (Sparus aurata) with an initial average weight of 170 g. Bio‐Mos was added at 2 or 4 g kg^?1 to a fish meal–based control diet, and each diet was fed to triplicate groups of 1‐year‐old gilthead sea bream. After 12 weeks, there were no differences in survival rate among fish fed experimental diets (P > 0.05). It was observed that a significant improvability existed for both growth and feed utilization in fish fed diets supplemented with Bio‐Mos (P < 0.05). Body proximate composition remained unaffected by Bio‐Mos supplementation in fish fed experimental diets (P > 0.05). Apparent digestibility values for protein, carbohydrate and energy were appreciably affected by the inclusion of two different levels of Bio‐Mos, only lipid digestibility was the exception. In conclusion, the results of this trial indicate that 2 g kg^?1 dietary supplementation with BIO‐MOS seem to be most positive for gilthead sea bream production.     

Effects of cyclic feeding on compensatory growth of hybrid striped bass (Morone chrysops×M. saxitilis) foodfish and water quality in production ponds

An 18‐week study was conducted in 12, 0.1 ha ponds to evaluate the impacts of cyclic feeding regimes on hybrid striped bass (HSB) foodfish production and pond water quality. Approximately 840 HSB [mean weight (std.); 91.08 g (8.18)] were stocked into each pond (8400 fish ha^?1; 3360 fish acre^?1) and fed according to one of three feeding regimes. The three feeding regimes included a control (fed twice daily to apparent satiation), and cycles of 3 weeks feed deprivation followed by 3 or 6 weeks of feeding to apparent satiation (3/3 and 3/6 respectively). Compensatory growth (CG) was observed in both cyclic feeding treatments; however, the response was insufficient for the fish to completely regain lost weight. Final mean weight of control fish (477.9 g) exceeded (P<0.05) that of fish receiving the two cyclic treatments: 3/6 (404.7 g) and 3/3 (353.8 g). Specific growth rate (SGR) of fish in the 3/3 treatment increased during all three refeeding periods, and was significantly greater than controls during weeks 9–12 and weeks 15–18, which represent the refeeding phase of the second and third feeding cycles. Specific growth rate for fish in the 3/6 treatment was significantly higher than controls only during the first 3 weeks of the first feeding cycle. Hepatosomatic index and condition factor were highly responsive measures that closely followed the metabolic state of fish on the feeding cycle. Of the water quality variables measured, total phosphorus was 32% lower in ponds receiving cyclic feeding versus control ponds. Soluble reactive phosphorus was 41% and 24% lower in ponds offered the 3/3 and 3/6 cyclic feeding treatments, respectively, although, significant differences (P<0.10) were only observed between control and 3/3 treatment ponds. Overall, CG was observed in HSB foodfish grown in ponds, although 3 weeks of feed deprivation was excessive and did not allow for complete growth compensation. Weight loss during feed deprivation was influenced by pond water temperatures. Early season feed deprivation did not cause as much weight loss as during the second cycle later in the season. Further studies on shorter deprivation periods applied during moderate to low water temperatures are needed to identify feeding regimes that minimize weight loss and result in a complete CG response.     

Combined Effects of Cycled Starvation and Feeding Frequency on Growth and Oxygen Consumption of Gilthead Sea Bream,Sparus aurata

Triplicate groups of gilthead sea bream, Sparus aurata (10.4 g), were distributed among 27 tanks (12 fish per tank) and reared in flow‐through seawater. A factorial experiment (3 × 3) was designed to include a continuously fed control group and two cycled starvation groups: 1 + 3 (starved 1 d, fed 3 d), 1 + 5 (starved 1 d, fed 5 d). Each of the feeding groups was subjected to one of three feeding frequencies (2, 4, and 6 times per day) over the 60‐d experiment duration. The average final weight of fish in 1 + 3 and 1 + 5 groups were significantly lower than that of the control group. Partial compensation was observed in the starved groups subjected to any of the three feeding frequencies. Regardless of the feeding frequency, control fish consumed less feed than the starved groups. The highest body protein content was found in the control group. The rate of oxygen consumption significantly increased 30 min after the feeding and the magnitude of the effect increased with the feeding frequency. These results suggest that the present cycling starvation schedules did not invoke a full compensation in gilthead sea bream.     

Application of Compensatory Growth to Enhance Production in Channel Catfish Ictalurus punctatus

Four treatment groups that received repeating cycles of fixed feed deprivation for either 0, 1, 2, or 3 d (control, treatment 1, treatment 2, and treatment 3, respectively), followed by periods of refeeding with a 36% protein commercial catfish feed once daily as long as the active phase of compensatory growth (CG) persisted, were assessed in flow-through aquaria. No-feed periods elicited the CG state and were immediately followed by days of ad libatum refeeding. At the end of 10 wk, average growth rate (AGR) of fish was higher ( P < 0.05) than the control by 40%, 180%, and 191% for treatment 1, treatment 2, and treatment 3, respectively. The average weight of fish in treatment 3 was heavier ( P < 0.05) than the average control group at the end of the study period. Mean daily feed consumption was 3.91%, 5.03%, 5.36%, and 5.98% for control, treatment 1, treatment 2, and treatment 3, respectively. Mean feed consumption per fish per day was 24%, 71.3%, and 70.7% higher than the control in treatment 1, treatment 2, and treatment 3, respectively. Restricted feeding is one of the effective methods to contain ESC-related losses in commercial channel catfish fingerling operations. The mean cumulative survival of treatment groups registered higher ( P < 0.05) survival to Edwardsiella ictaluri infection compared to the daily fed control fish. Results from this study show that compensatory growth response triggered by periodic non-feeding days can improve growth rate, feed consumption, and improved survival to ESC infections in channel catfish fingerlings.     

Effect of the squid viscera hydrolysate on growth performance and digestion in the red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

The improvement in feed efficiency is one of the most important subjects in fish culture. The development of feed, in terms of good intake, high growth performance, and high feed efficiency is needed. Squid viscera are one of the candidates for alternative material in improving feed efficiency in fish culture. In the present study, we described the dietary effect of the squid viscera hydrolysate (SVH) on the growth performance of the red sea bream. The addition of SVH to feed caused significant increases in feed intake, fork length, and body weight and produced a marked improvement in feed conversion after 4 weeks of feeding. Furthermore, the results of this feeding revealed that low dietary levels of SVH promote growth performance in the red sea bream. We physiologically analyzed digestion and appetite in fish fed diet containing SVH. SVH promoted the activity of hepatic trypsin and lipase, gene expression of stomach pepsin, hepatic lipase, and pyloric caeca trypsin, thereby improving the nutrient availability in red sea bream. Moreover, the mRNA expression of appetite regulating factor, such as brain NPY and stomach ghrelin was significantly improved by dietary SVH. Our current results indicate that dietary SVH as alternative material produced excellent effects on growth performance, which is dependent on the promoting effect on digestion and appetite in red sea bream.     

Effects of dietary mannan oligosaccharides in early weaning diets on growth,survival, fatty acid composition and gut morphology of gilthead sea bream (Sparus aurata,L.) larvae

Early weaning of marine fish larvae with dry diets delays gut maturation and reduces growth rates. In juvenile and adult forms of several marine fish species, inclusion of dietary mannan oligosaccharides (MOS) improves gut integrity and functionality, but the effects of MOS inclusion in gilthead sea bream (Sparus aurata, L.) larval diets have not been addressed yet. Thus, this study assesses the effects of dietary MOS inclusion on survival, growth performance, gut morphology, feed acceptance and quality of gilthead sea bream larvae. For that purpose, 16 days post‐hatched gilthead sea bream larvae were fed four graded levels of MOS (Biomos^®, Alltech, Nicholasville, KY, USA) in weaning diets as follows: 0 g kg^?1 MOS, 0.5 g kg^?1 MOS, 1.5 g kg^?1 MOS and 2 g kg^?1MOS. Dietary MOS did not affect feed acceptance in gilthead sea bream larvae (P > 0.05). MOS supplementation was correlated in a dose‐dependent way with higher larval survival (P = 0.026). After 15 days of feeding, dietary MOS increased whole larvae (P < 0.01) arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Gilthead sea bream larvae fed 2 g kg^?1 MOS presented higher gut occupation with goblet cells after feeding compared with larvae fed the other dietary treatments. Overall, the results suggest that inclusion of MOS in early weaning diets for gilthead sea bream improves essential fatty acid utilization and may promote growth and final survival.