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1.
Largemouth bass (LMB), Micropterus salmoides, are a highly desirable food fish especially among Asian populations in large cities throughout North America. The primary production method for food‐size LMB (>500 g) has been outdoor ponds that require two growing seasons (18 mo). Indoor, controlled‐environment production using recirculating aquaculture system (RAS) technologies could potentially reduce the growout period by maintaining ideal temperatures year‐round. Researchers conducted a 26‐wk study to evaluate optimal stocking densities for growout of second‐year LMB to food‐fish size in an indoor RAS. LMB fingerlings (112.0 ± 38.0 g) were randomly stocked into nine 900‐L tanks to achieve densities of 30, 60, or 120 fish/m3 with three replicate tanks per density. The RAS consisted of a 3000‐L sump, ¼ hp pump, bead filter for solids removal, mixed‐moving‐bed biofilter for nitrification, and a 400‐watt ultraviolet light for sterilization. Fish were fed a commercially available floating diet (45% protein and 16% lipid) once daily to apparent satiation. At harvest, all fish were counted, individually weighed, and measured. Total biomass densities significantly increased (P ≤ 0.05) with stocking rate achieving 6.2, 13.2, and 22.9 kg/m3 for fish stocked at 20, 60, and 120 fish/m3, respectively. The stocking densities evaluated had no significant impact (P > 0.05) on survival, average harvest weight, or feed conversion ratio which averaged 92.9 ± 5.8%, 294.5 ± 21.1 g, and 1.8 ± 0.3, respectively. After approximately 6 mo of culture, LMB did not attain target weights of >500 g. Observed competition among fish likely resulted in large size variability and overall poor growth compared to second‐year growth in ponds. Additional research is needed to better assess the suitability of LMB for culture in RAS.  相似文献   

2.
An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate compensatory growth and body composition in African catfish Clarias gariepinus (13.05 ± 0.05 g). A fishmeal‐based diet containing 350 g kg?1 protein and 17.5 kJ g?1 gross energy was fed to triplicate groups of 20 fish (per 30‐L tank). Fish were fed the diet either to satiation or feed restricted in six feeding schedules as satiation 56 days; restricted 28 days + satiation 28 days; restricted 14 days + satiation 14 days; restricted 7 days +satiation 7 days; restricted 3 days + satiation 4 days; and restricted 2 days + satiation 2 days. The restricted regime was achieved by offering fish 1% (maintenance ration) of their body weight per day adjusted after fortnightly weighing. African catfish showed partial compensatory growth under alternating periods of feed restriction and satiation feeding with significantly different values (P < 0.05) from fish fed in satiation throughout. However, significantly indifferent (P > 0.05) values of feed, protein, lipid and energy utilization were found under alternating periods of feed restriction and satiation feeding. Significantly higher (P < 0.05) feed intake was observed in treatment with satiation throughout than those in other treatments. All the feeding schedules showed no significant differences (P > 0.05) on body composition, organ indices, eviscerated carcass composition, viscera lipid and liver lipid. These studies reveals that C. gariepinus showed partial compensatory growth responses at alternating periods of restricted and satiation feeding.  相似文献   

3.
A study to determine the effects of four stocking densities on growth and feed utilization of wild‐caught black sea bass Centropristis striata was conducted in a pilot‐scale recirculating tank system. The outdoor system consisted of 12 insulated fiberglass tanks (dia. = 1.85 m; vol. = 2.17 m3) supported by biological filters, UV sterilizers, and heat pumps. Subadults (N= 525; ×± SD = 249 ± 16.8 g) were stocked at densities of 4.6 fish/m3 (1.18 kg/m3), 16 fish/ m3 (3.91 kg/m3), 25.3 fish/m3 (6.83 kg/m3), and 36 fish/m3 (7.95 kg1m3), with three replicate tanks per treatment. Fish were grown under 35 ppt salinity, 21‐25 C, and under ambient photoperiod conditions. A commercial flounder diet containing 50% protein and 12% lipid was hand‐fed twice daily to satiation for 201 d. Mean (range) total ammonia‐nitrogen, 0.61 (0‐2.1) mg/L, nitrite‐nitrogen, 0.77 (0.04‐3.6) mg/L, and nitrate‐nitrogen 40.1 (0‐306) mg/L were significantly higher (P < 0.0001) in the 25.3 and 36 fish/m3 treatments than in the 4.6 and 16 fish/m3 treatments [0.19 (0.05‐0.5), 0.1 (0.24‐0.63), and 11.9 (1.3‐82.2) mg/L, respectively]. However, there were no significant differences (P > 0.05) in growth (RGR = 196.8‐243.1%; DWG = 2.55‐2.83 g/d; and SGR = 0.55‐0.61%/d), coefficient of variation of body weight (CwtV., = 0.24‐0.25), condition factor (K = 2.2‐2.4), feed consumption (FC = 1.45‐1.65%/d), and feed conversion ratio (FCR = 1.45‐1.52) among stocking densities. Final biomass densities on day 201 reached 3.48, 12.0, 21.1, and 27.2 kg/m3 at stocking densities of 4.6, 16, 25.3, and 36 fish/m3, respectively. Survival (83.8‐99.1%) did not differ among treatments. Apparent net protein retention (ANPR) was significantly higher (P < 0.005) for fish stocked at the lower densities of 4.6 and 16 fish/m3 (22.5‐23.7%) than for those stocked at 25.3 and 36 fish/m3 (21‐20.1%). There were no significant differences (P > 0.05) in apparent net energy retention (ANER = 55.9‐59.1 %) among stocking densities. Final whole body protein (15.3‐16.3%) and lipid (23.1‐26.4%) levels did not differ significantly (P > 0.05) among treatments. The results demonstrated that growth, survival, and feed utilization were not impaired under stocking densities ranging from 4.6‐36 fish/m3 (3.48‐27.2 kg/m3), despite a slight reduction in water quality at the higher densities. In addition, growth variation and final whole body protein and lipid levels were not influenced by these densities. The results suggest that black sea bass are tolerant of crowding and moderate variations in water quality during intensive culture in recirculating tank systems and that higher stocking densities are possible.  相似文献   

4.
Development of efficient cost‐effective diets is a critical component in the refinement of production technologies for the largemouth bass, Micropterus salmoides (LMB). One of the first steps in reducing feed costs can be to decrease the amount of fish meal in the diet. The objective of this study was to evaluate reduced levels of fish meal, and a least‐cost formulation diet, for second year growout of LMB under practical pond conditions. Twelve 0.04‐ha ponds were stocked with juvenile LMB (210.1 ± 3.3 g) at a stocking density of 8650 fish/ha (350 fish/pond). Each pond was randomly assigned one of the four dietary treatments with three replicate ponds per treatment. The three experimental diets contained varying levels of fish meal. Diets FM‐45, FM‐24, and FM‐8 contained 45, 23.5, and 8% fish meal, respectively. In diets FM‐24 and FM‐8, fish meal was replaced by varying levels of poultry by‐product meal, soybean meal, and blood meal. The fourth diet was a commercial salmonid diet widely used as a LMB growout feed (Nelson and Sons, Inc., Silvercup TM , Steelhead, Murray, UT, USA). This diet served as a commercial control (CC) and contained 46% crude protein. The experimental diets were formulated to be isonitrogenous and isocaloric with the CC diet and were fed once daily to apparent satiation for 180 d. At harvest, there were no significant differences between treatments ( P > 0.05 ) in terms of survival, which averaged 95% overall. Mean weights of fish fed the three experimental diets FM‐45, FM‐24 and FM‐8 were not significantly different ( P > 0.05 ) and averaged 518, 546, and 529 g, respectively, but were all significantly greater ( P≤ 0.05 ) than those fed the CC (488 g). Feed conversion ratio (FCR) of fish fed the FM‐45 and FM‐8 diets (1.43 and 1.46, respectively) was significantly greater ( P≤ 0.05 ) than those fed the FM‐24 diet (1.34). The FCR of fish fed the CC diet (1.39) was not significantly different ( P > 0.05 ) from fish fed other diets. Feed cost per unit of weight gain ($US/kg) was significantly lower ( P≤ 0.05 ) in fish fed the FM‐24 and FM‐8 diets ($0.73 and $0.72/kg, respectively) than in fish fed other diets. Feed cost per unit gain of fish fed the FM‐45 diet ($0.83/kg) was significantly lower ( P≤ 0.05 ) than those fed the CC diet ($1.04/kg). There were no significant differences ( P > 0.05 ) in dress‐out percentages or proximate composition among fish fed the four diets. This study indicates that fish meal levels in feeds used for the second year growout of LMB can be reduced to ≥ 8% of the formulation without reducing survival or growth and without negatively impacting body composition.  相似文献   

5.
The role of restricted feeding on the growth and feed efficiency (FE) of juvenile walleye, Sander vitreus, was investigated through two experiments. In the summer/fall experiment, 7.44‐g walleye were fed on one of the three schedules for 84 days: control (daily satiation feeding at 6% BW day?1), D2 (2 days of feed deprivation, then fed at 12% BW day?1 for 7 days, repeated throughout the study) and SS80 (subsatiation feeding involving 2 weeks of maintenance ration, then fed at 80% of the control group's feeding level). Juvenile walleye growth rates were significantly higher in the SS80 than in the control group, however, their growth rates in the D2 group were no different than in the control. Mean FE of the SS80 group (0.49), significantly exceeded those of the control (0.36) and D2 (0.28) groups. In contrast with the summer/fall experiment, no differences in growth rate were detected among the control, SS80 and D2 groups in the subsequent 84‐d spring experiment, where the juvenile walleye (97.45 g) were substantially larger, and their mean FE values were generally lower, with less distinction observed among the groups. Our findings indicate potential to increase growth and FE of juvenile walleye in advance of fall, by applying restrict‐feed schedules.  相似文献   

6.
Effects of varying protein‐to‐energy (P/E) ratios on growth performance, nutrient retention, body composition, and digestive enzyme activities of Singhi, Heteropneustes fossilis (7.90 ± 0.40 g; 9.40 ± 0.20 cm) were evaluated. Six experimental diets (350Low, 350High, 400Low, 400High, 450Low, and 450High) in a 3 × 2 factorial design were formulated to contain three protein levels (350, 400, and 450 g/kg crude protein) and two energy levels (4.07 and 4.54 kcal/g gross energy [GE]) to provide six different dietary P/E ratios (86.1, 77, 98.3, 88, 110.6, and 99 mg protein/kcal GE). The diets were hand‐fed to triplicate groups of fish for 84 d to apparent satiation at two feeding frequencies. Live weight gain, feed conversion ratio, protein retention efficiency, energy retention efficiency, somatic indices, and digestive enzyme activities were maximized by the groups fed on 400 g/kg protein with 4.07 kcal/g GE in diet 400Low with a P/E ratio of 98.3 mg/kcal energy. The results indicate that 400 g/kg of dietary protein and 4.07 kcal/g of dietary GE with a P/E ratio of 98.3 mg protein/kcal energy is optimum for achieving efficient growth, feed conversion, and nutrient retention in H. fossilis.  相似文献   

7.
Effect of varying dietary lysine levels on growth, feed conversion, nutrient retention, lysine retention efficiency and haematological indices of Heteropneustes fossilis fry (2.97 ± 0.11 cm; 4.78 ± 0.31 g) was studied by conducting a 12‐week feeding trial. Isonitrogenous (450 g kg?1 CP) and isocaloric (17.97 kJ g?1 GE) amino acid test diets with graded concentrations of l ‐lysine (18, 20, 22, 24, 26, 28 g kg?1 dry diet) were fed to triplicate groups of fish to apparent satiation twice daily at 17 and 17:30 h. Maximum thermal growth coefficient (TGC, 0.82), best feed conversion ratio (FCR, 1.28) highest protein retention efficiency (PRE, 36%), energy retention efficiency (ERE, 79%) and lysine retention efficiency (LRE, 75%) were noted at 24 g kg?1 lysine of dry diet. Body protein was also found to be in line with growth data and peaked at 24 g kg?1 lysine of dry diet. Similarly, superior somatic and haematological indices were exhibited by the groups fed dietary lysine at 24 g kg?1 of the dry diet. However, exponential analysis of dietary lysine intake against TGC, lysine retention and protein retention indicated that inclusion of dietary lysine in the range of 13.24–14.14 g kg?1 dry diet, corresponding to 29.42–31.42 g kg?1 dietary protein, is essential for faster growth of this fish.  相似文献   

8.
An assessment of the nutritive value of palm kernel meal (PKM) and aflatoxin‐contaminated PKM (obtained by fermenting PKM with Aspergillus flavus) as a dietary ingredient in pelleted feed for tilapia, Oreochromis mossambicus Peters, was carried out in a 12‐week feeding trial. Seven isonitrogenous (40% crude protein) and isoenergetic (15.1 kJ g?1) practical diets were formulated and fed close to apparent satiation to triplicate groups of 12 fish (mean initial weight 8.4 ± 0.1 g). The control diet contained 30% fish meal and 10% soybean meal (SBM) proteins. Four other experimental diets containing 20% and 50% of the SBM protein replaced by either PKM or fermented PKM, respectively, were formulated. Two additional diets containing either PKM or fermented PKM supplemented with a commercial aflatoxin adsorber (0.5% SorbatoxTM) were also formulated. Measured aflatoxin B1 levels in the fermented PKM‐based diets ranged from 75 to 100 µg kg?1 diet. The growth performance and feed utilization efficiency of tilapia fed fermented PKM‐based diets were significantly lower than in fish fed the control diet at all inclusion levels (P < 0.05). Despite a small reduction, weight gains of tilapia fed PKM‐based diets were not significantly different compared with fish fed the control diet. The addition of 0.5% Sorbatox did not produce any beneficial or negative effects to the growth of tilapia. Under the dietary conditions of the present experiment, it was concluded that PKM can substitute up to 50% SBM in practical diets for O. mossambicus without much adverse effect to fish growth. However, when PKM was contaminated with A. flavus, its' incorporation into tilapia diets resulted in growth depression as a result of decreased diet digestibility and also possibly because of the presence of anti‐nutrients found in the contaminated PKM.  相似文献   

9.
Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day?1 and satiation (5.52% BW day?1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day?1 and satiation (4.12% BW day?1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day?1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day?1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day?1 whereas FE reached a plateau at 3.0% BW day?1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day?1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day?1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day?1 for 5.0 g, and it could be >3.0 but <3.47% BW day?1 for 20 g size of juvenile olive flounder at the optimum rearing temperature.  相似文献   

10.
An experiment to investigate the compensatory growth (CG) response of Labeo rohita was conducted in two phases: a first phase (6 weeks) in which triplicate groups of fish were subjected to feed restriction (5, 25, 50 and 75 % of satiation) or satiation feeding (control) and a second phase (6 weeks) of satiation feeding for all treatment groups. CG in body weight occurred in groups which were under moderate feed restriction (50–75 % of satiation) under phase 1, but more severe feed restrictions resulted in lower weight gain. Improved feed conversion ratio (FCR) (1.6 ± 0.05 and 1.9 ± 0.03) relative to control (2.1 ± 0.06) was observed in the fish that displayed CG following moderate feed restriction (50–75 % of satiation). At the end of the experiment, body moisture, lipid and protein content were not significantly different between moderately restricted fish and the control. After the first phase, there was no significant difference in the expression of pituitary growth hormone (GH) gene between groups, but at the end of the experiment, significantly lower GH expression was observed in the fish subjected to a restriction of 25 and 50 % of satiation during phase 1. Exploiting the ability of fishes to undergo CG in terms of weight gain and improved FCR without major changes in body composition can be considered as an effective management practice.  相似文献   

11.
The potential of rapeseed protein concentrate as fish meal alternative in diets for wels catfish (initial average weight 86.5 ± 1.9 g) was evaluated. Sixteen fish were stocked into each of 12 experimental tanks being part of a freshwater recirculation system. Fish were organized in triplicate groups and received isonitrogenous (603 ± 3 g CP kg?1) and isocaloric (23.0 ± 0.3 kJ g?1) experimental diets with 0%, 25%, 50% and 75% of fish meal replaced with rapeseed protein concentrate (710 g CP kg?1). At the end of the 63‐day feeding period, weight gain, standard growth rate, feed intake, feed conversion ratio and protein efficiency showed no significant difference between control group and fish fed on diets with 25% reduced fish meal content by inclusion of rapeseed protein concentrate. Higher dietary fish meal replacement negatively affected diet quality and palatability resulting in reduced feed intake, feed efficiencies and fish performance. However, blood serum values of triglycerides, glucose and protein were not significantly different between treatment groups, still indicating a favourable nutrient supply from all experimental diets.  相似文献   

12.
Growout production of the camouflage grouper, Epinephelus polyphekadion (Bleeker), in a 10-m3-capacity fibreglass tank culture system was evaluated, using hatchery-produced fingerlings (56-59 g initial weight) at stocking densities of five, 15 and 45 fish m?3. During the first 9 months of a 12-month growout period, the fish were fed twice a day with a moist pellet feed containing 40.9% protein. From month 10 onwards until harvest, the fish were fed moist pellets in the morning and trash fish in the evening at a 1:1 ratio. The final weight of fish at harvest was up to 900 g, with mean weights of 544.6 ± 170.72 g at five fish m?3, 540.2 ± 150.82 g at 15 fish m-?3 and 513.3 ± 134.52 g at 45 fish m?3. The results showed no significant differences (P > 0.05) in growth rate and fish size between the different stocking densities tested. The average daily growth rate ranged from 0.62 to 3.38 g fish?1 day?1, with mean weights of 1.49 ± 0.74 g fish?1 day?1 at five fish m?3 through 0.53 to 2.38 g fish?1 day?1, 1.32 ± 0.57 g fish?1 day?1 at 15 fish m?3 to 0.48-3.32 g fish?1 day?1 and 1.31 g fish?1 day?1 at 45 fish m?3 stocking density. Although up to 100% survival was observed at the lowest stocking density, the survival rate significantly decreased (P < 0.05) with increasing stocking density. The food conversion ratio (FCR) significantly decreased (P <0.05) with increasing stocking densities, showing efficient feed utilization with increasing stocking densities of E. polyphekadion. The FCR averaged 2.1 at a stocking density of 45 fish m?3. The yield in terms of kg fish produced m?3 of water used in the culture system significantly increased (P < 0.001) from five to 45 fish m?3. The yield averaged 17.3 ±0.53 kg m?3 at a stocking density of 45 fish m?3. The present results show that the present tank culture system could sustain more biomass in terms of increasing fish stocking densities. The growth performance of E. polyphekadion observed during this investigation has been reviewed with other grouper species.  相似文献   

13.
Critical evaluation of the nutrient requirements of an animal requires the use of a purified reference diet. In this study, the effects of either a purified reference experimental diet, a practical experimental diet and an imported commercial diet on the growth and nutritional condition of the prawn Penaeusmonodon were compared. The reference diet, based on widely available ingredients of consistent and known nutrient content, supported excellent prawn growth when fed either ad libitum or subsatiation (≈ 75% of the mean initial satiation intake). In a 6-week experiment, growth (as percentage increase in weight, ± SEM) of the prawns fed ad libitum differed significantly (P < 0.05) between each diet in the order: practical (142 ± 10%), reference (121 ± 9%) and commercial (91 ± 16%). Growth for the reference diet fed subsatiation was 116 ± 4%, and was not significantly (P > 0.05) different from that obtained with the same diet fed ad libitum. Dry matter food conversion for the reference diet was significantly (P < 0.05) better when fed subsatiation (1.58 ± 0.08) rather than ad libitum (2.08 ± 0.06) and better than that obtained with either the practical (3.40 ± 0.15) or commercial (3.02 ± 0.28) diets, which were not significantly (P > 0.05) different from each other. The lipid content (mg g–1 of prawn) of the digestive gland of prawns fed ad libitum was similar for reference, practical and commercial diets (6.03 ± 0.38, 4.92 ± 0.90 and 4.92 ± 0.95 mg g–1 of prawn, respectively), but significantly (P < 0.05) higher than that for the reference diet fed subsatiation (4.73 ± 0.38 mg g–1 of prawn).  相似文献   

14.
A 6‐wk feeding trial was conducted to evaluate the effects of different dietary lipid levels and feeding frequencies on the growth performance, feed utilization, and body composition of juvenile spotted seabass, Lateolabrax maculatus. Two experimental diets were prepared with two different dietary lipid contents, low lipid (7%; LL) and high lipid (14%; HL). Each diet was fed to triplicate groups of fish (5.5 ± 0.01 g) to apparent satiation at three meals per day, two meals per day, one meal per day, and one meal every 2 d, respectively, for 6 wk. Fish growth performance in terms of weight gain (WG) and specific growth rate (SGR) was significantly affected by frequency of feeding, with increasing values as feeding frequency increased up to twice daily, regardless of dietary lipid content. In addition, fish fed the diet with the HL level (14%) showed significantly higher WG and SGR than those fed the LL diet (7%) at all the feeding frequencies tested. Feed efficiency (FE) and protein efficiency ratio (PER) were affected by both dietary lipid level and feeding frequency. FE and PER values were significantly higher in fish fed the HL diet and/or when fish were fed twice or thrice a day. However, daily feed intake and daily energy intake were significantly affected only by feeding frequency and were significantly reduced when the fish were fed only once every 2 d compared with those fed more frequently. Whole‐body moisture content of fish tended to decrease with increasing dietary lipid level and frequency of feeding. In contrast, whole‐body lipid content increased in fish as dietary lipid level and feeding frequency increased. Consequently, we can conclude that feeding spotted seabass twice daily to apparent satiation is acceptable and sufficient to achieve good growth and FE, as fish performance was not significantly enhanced when feeding was increased from two to three times daily.  相似文献   

15.
A 2 ± 4 factorial experiment was conducted to examine effects of dietary protein level (28, 32, 36, and 40%) and feeding rate (satiation or ± 90 kg/ha per d) on production characteristics, processing yield, body composition, and water quality for pond-raised channel catfish Ictalurus punctatus. Fingerling channel catfish with a mean weight of 64 g/fish were stocked into 40 0.04-ha ponds at a rate of 17,290 fish/ha. Fish were fed once daily to apparent satiation or at a rate of ± 90 kg/ha per d for 134 d during the growing season. Dietary protein concentration had no effect on feed consumption, weight gain, feed conversion, survival, aeration time, or on fillet moisture, protein, and fat levels. Fish fed to satiation consumed more feed, gained more weight, had a higher feed conversion, and required more aeration time than fish fed a restricted ration. Visceral fat decreased, and fillet yield increased as dietary protein concentration increased to 36%. Carcass yield was lower for fish fed a diet containing 28% protein. Increasing feeding rate increased visceral fat but had no major effect on carcass, fillet, and nugget yields. Fish fed to satiation contained less moisture and more fat in the fillets that those fed a restricted ration. Nitrogenous waste compounds were generally higher where the fish were fed the higher protein diets. Although there was a significant interaction in pond water chemical oxygen demand between dietary protein and feeding rate, generally ponds in the satiation feeding group had higher chemical oxygen demand than ponds in the restricted feeding group. There was a trend that pond water total phosphorus levels were slightly elevated in the satiation feeding group compared to the restricted feeding group. However, pond water soluble reactive phosphorus and chlorophyll-a were not affected by either diet or feeding rate. Results from the present study indicate that a 28% protein diet provides the same level of channel catfish production as a 40% protein diet even when diet is restricted to 90 kg/ha per d. Although there was an increase in nitrogenous wastes in ponds where fish were fed high protein diets, there was little effect on fish production. The long term effects of using high protein diets on water quality are still unclear. Feeding to less than satiety may be beneficial in improving feed efficiency and water quality.  相似文献   

16.
ABSTRACT

A 14-week feeding experiment was conducted to determine the effect of a time-restricted feeding and refeeding regime on compensatory growth, body composition, and feed utilization in improved traditional prawn (Macrobrachium rosenbergii) culture systems. Three groups of prawn were used in which the control group (C) received feed regularly at ad libitum and the other two groups, Treatment 1 (T1) and Treatment 2 (T2), consumed feed 4 and 5 days per week respectively throughout the first 9 weeks. After feeding restriction, satiation of feed was given in the last 5 weeks. At the end of the experiment, the final weight of prawn in C, T1, and T2 were found to be 17.23 ± 6.56g, 16.04 ± 6.18g, and 15.64 ± 6.34 g respectively, which was insignificant. FCR decreased with increased restriction of feeding, while PER and NPU increased. Moisture content increased significantly, while protein and lipid content decreased significantly with increasing restriction time of feeding. After the satiation period, only the T2 group was able to replenish the lipid content. Water quality parameters didn’t vary significantly among the experimental groups and remained within optimum level. Therefore, time restriction could be applied in Macrobrachium rosenbergii culture without detrimental effects on growth, feed efficiency, and nutrient utilization.  相似文献   

17.
Two experiments were conducted to examine the effect of commercially available beta‐glucan (Macrogard) and nucleotide (Aquagen) on the resistance to Streptococcus iniae infections in vaccinated or nonvaccinated juvenile red‐tail black sharks (Epalzeorhynchos bicolor, RTB) (1.4 ± 0.4 g weight total (WT), 5.6 ± 0.5 cm total length (TL)). The immunostimulants were added to a control diet formulated without any yeast source following the recommended doses of 1 g/kg feed for the beta‐glucan and 2 g/kg feed for the nucleotide. Beginning 4 d after introduction into tanks, fish were fed the experimental diets for 24 d, at 3% body weight per day, divided into two feedings. At the end of this period, fish were challenged by an intracoelomic injection of S. iniae. In the first experiment, both vaccinated and nonvaccinated fish were fed one of the two immunostimulants. In the second experiment, only vaccinated fish were fed the immunostimulants. Fish were vaccinated a week after being introduced into the system and challenged by intracoelomic injection with 1.5 × 105 S. iniae colony‐forming units /fish after three additional weeks; mortality was recorded for 2 wk after the bacterial challenge. In the first experiment, the mortality of both vaccinated and nonvaccinated fish fed beta‐glucan (23 ± 7% and 82 ± 1%, respectively) or nucleotide (28 ± 6% and 86 ± 5%, respectively) was significantly lower than the mortality of the control groups (35 ± 4% and 93 ± 5%, respectively), but there was no significant difference in mortality between fish fed beta‐glucan or nucleotide. In the second experiment, the mortality of vaccinated fish fed beta‐glucan (25 ± 7%) or nucleotide (43 ± 9%) was significantly lower than that of vaccinated fish fed the control diet (69 ± 7%). In both experiments, there was no significant difference in growth rate among fish fed immunostimulants or the control diet. The results of this investigation demonstrated the efficacy of beta‐glucans and nucleotides in increasing resistance to S. iniae in RTB sharks.  相似文献   

18.
This study evaluated the growth (first phase) and feeding responses (second phase) of juvenile mutton snapper fed four isonitrogenous and isoenergetic diets with increasing levels of soy protein concentrate (SPC) in substitution to fish meal (FM). The FM was replaced by SPC at 0% (basal diet, SPC000), 33% (SPC130), 57% (SPC214) and 77% (SPC300). After 95 days of rearing, fish fed SPC300 attained a significantly lower body weight (54.9 ± 13.2 g) compared with those fed diets SPC000, SPC130 and SPC214 (76.5 ± 14.0 g, 73.9 ± 13.8 g and 70.5 ± 14.0 g respectively). Fish yield increased significantly from 891 ± 36 g m?3 for fish fed SPC300 to an average of 1099 ± 111 g m?3 for other diets. A maximum fish body weight gain of 0.60 ± 0.05 g day?1 and a maximum specific growth rate of 1.47 ± 0.07% day?1 were achieved for SPC000. Behavioural assays conducted during 10 days revealed the loss in fish growth with diets containing higher levels of SPC was due to a decline in feed intake. Low feed intake driven by a poor feed palatability appeared to have been a major obstacle against higher inputs of SPC in diets for mutton snapper.  相似文献   

19.
The aim of this study was to evaluate whether pretreatment of palm kernel meal (PKM) with a commercial feed enzyme (Allzyme Vegpro?) or solid‐state fermentation of PKM with the cellulolytic fungus Trichoderma koningii (Oudemans) could improve the nutritive value of raw PKM in the diets of red hybrid tilapia, Oreochromis sp. Seven isonitrogenous (30% crude protein) and isoenergetic (15.1 kJ g?1) practical diets were formulated and fed close to apparent satiation to triplicate groups of 14 fish (mean initial weight 5.1 ± 0.1 g) for 10 weeks. The diets consisted of a control diet which did not contain any PKM, raw PKM diets, enzyme‐treated PKM (EPKM) or fermented PKM (FPKM) diets at 20% and 40% (dry weight basis) inclusion rates. The growth performance and feed utilization efficiency of tilapia fed 20% PKM or 20% EPKM were not significantly different (P > 0.05) from those of fish fed the control diet. Fish fed diets containing 40% EPKM showed significantly higher growth and feed utilization efficiency than fish fed 40% raw PKM owing to the improved dry matter, protein, lipid and energy digestibility of the enzyme‐treated PKM diets. The apparent protein and lipid digestibility of the 20% EPKM and 40% EPKM diets were not significantly different, and nor was the growth and feed utilization efficiency of fish fed these two diets. Hybrid tilapia fed FPKM‐based diets at all dietary inclusions tested showed the poorest growth, and this might indicate the presence of antinutrients in the resultant fungal biomass. In conclusion, it is anticipated that, with further optimization of enzyme pretreatment of PKM, higher levels of PKM could be included in the diets of hybrid tilapia, thereby reducing the impact of rising costs to feed tilapia.  相似文献   

20.
Previous research and experience has linked elevated dissolved carbon dioxide (CO2) to reduced growth performance, poor feed conversion, and a variety of health issues in farm-raised fish, including Atlantic salmon Salmo salar. Supplemental control measures in water recirculation aquaculture systems (RAS) to reduce CO2 accumulation, however, such as increased water pumping to decrease tank hydraulic retention time, can represent significant costs for operators. We exposed post-smolt S0 Atlantic salmon (197 ± 2 g, 423 days post-hatch) to either high (20 ± 1 mg/L) or low (8 ± <1 mg/L) dissolved CO2 in six replicated freshwater RAS for 384 days to investigate differences in performance and health as the salmon were grown to harvest size. All RAS were operated at moderate water exchange rates (1.0% of the total recirculating flow), a 24-h photoperiod was provided, fish were fed to satiation, and densities were maintained between 40 and 80 kg/m3. Over the study period, dissolved oxygen was kept at saturation, mean water temperature was 14.1 ± 0.1 °C, and alkalinity averaged 237 mg/L as CaCO3. At study’s end, no significant differences in fish weight (high CO2 mean weight = 2879 ± 35 g; low CO2 mean weight = 2896 ± 12 g), feed conversion ratio (1.14 ± 0.12 vs. 1.22 ± 0.13, respectively), or thermal growth coefficient (1.45 ± 0.01 vs. 1.46 ± 0.01, respectively), were observed. No significant differences in survival (high CO2 mean survival = 99.1 ± 0.4%; low CO2 mean survival = 98.9 ± 0.3%) or culls due to saprolegniasis (3.5 ± 1% vs. 3.0 ± 1%, respectively) were determined, and no nephrocalcinosis was observed through histopathological evaluation. Blood gas and chemistry evaluation revealed higher pCO2, bicarbonate, and total CO2, and lower chloride and glucose, in the high CO2 cohort. Molecular analyses of gill enzyme regulation showed significantly higher expression of Na+/K+ ATPase α1a in high CO2 fish at 3-weeks post-challenge, indicating physiological adaptation to the higher CO2 environment without any noticeable long-term impacts on health or performance. Overall, the results of this study suggest that, at 237 mg/L as CaCO3 mean alkalinity, post-smolt Atlantic salmon can be raised in freshwater RAS to harvest size with up to 20 mg/L CO2 without significantly impacting fish health and performance.  相似文献   

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