Effect of time-restricted feeding and refeeding regimes on compensatory growth,body composition,and feed utilization in prawn (Macrobrachium rosenbergii) culture system

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.     

Evaluation of mixed feeding schedules with respect to compensatory growth and body composition in African catfish Clarias gariepinus

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.     

Effect of feed restriction on the growth performance of turbot (Scophthalmus maximus L.) juveniles under commercial rearing conditions

Two trials were performed to study the effect of periodic feed deprivation (trial 1) or feed restriction, followed by satiation feeding (trial 2) on the growth performance of turbot juveniles under commercial rearing conditions. In trial 1, duplicate groups of 350 fish with an initial weight of 62 g were fed a commercial diet to apparent visual satiation for 7, 6, 5 or 4 days a week for 83 days. At the end of the trial, fish weight was directly related to the number of feeding days but feed efficiency and protein efficiency ratio were not affected by treatments. At the end of the trial, there were no differences in whole‐body composition among groups. In trial 2, duplicate groups of 500 fish with an initial weight of 33 g were fed a commercial diet to satiation (100%) or feed restricted to 90%, 80% and 70% of satiation for 90 days. Thereafter, all groups were fed to satiation for 34 days. During the feed restriction period, growth was directly related to feed intake, while during the satiation feeding period, it was inversely related to the previous feeding level. At the end of the trial, the final weight was not different among groups. At the end of the feed restriction period, whole‐body lipid content showed a trend to decrease with an increase in the feed restriction level. The results of this study indicate that under practical conditions, turbot juveniles should be fed daily as even cycles of short periods of feed deprivation negatively affect growth, while not improving feed efficiency. On the contrary, even after a relatively long feed restriction period, fish shows compensatory growth, and this may be used as a feed management strategy for controlling fish production in commercial farms.     

Pilot Production of Hatchery-Reared Summer Flounder Paralichthys dentatus in a Marine Recirculating Aquaculture System: The Effects of Ration Level on Growth, Feed Conversion, and Survival

Pilot‐scale trials were conducted to evaluate growout performance of hatchery‐reared summer flounder fingerlings in a state‐of‐the‐art recirculating aquaculture system (RAS). The outdoor RAS consisted of four 4.57‐m dia × 0.69‐m deep (vol. =11.3 m³) covered, insulated tanks and associated water treatment components. Fingerlings (85.1 g mean initial weight) supplied by a commercial hatchery were stocked into two tanks at a density of 1,014 fish/tank (7.63 kg/m³). Fish were fed an extruded dry floating diet consisting of 50% protein and 12% lipid. The temperature was maintained between 20 C and 23 C and the salinity was 34 ppt. Under these conditions, growth, growth variation (CV_wt), feed utilization, and survival of fish fed to 100% and 82% of a satiation rate were compared. Due to clear changes in growth patterns during the study, data was analyzed in three phases. During phase 1 (d 1–d 196), fish showed rapid growth, reaching a mean weight of 288 g ± 105 and 316 g ± 102, with a CV_wt of 0.36 and 0.32 and FCR's of 1.38 and 1.36 in the subsatiation and satiation groups, respectively. During phase 2 (d 196–d 454), fish displayed slower growth reaching mean weights of 392 g ± 144 and 436 g ± 121, with a CV_wt of 0.37 and 0.28, and increasing FCR's of 3.45 and 3.12 in the subsatiation and satiation groups, respectively. During phase 3 (d 454–d 614), fish showed little growth reaching mean weights of 399 g ± 153 and 440 g ± 129, with a CV_wt of 0.38 and 0.29 in the subsatiation and satiation groups, respectively. Over the entire growout period (d 1–d 614), feed conversion ratios were 2.39 and 2.37 and survival was 75% and 81 % in the subsatiation and satiation treatments, respectively. The maximum biomass density reached during the study was 32.3 kg/m³. The satiation feed rate was superior to the 82% satiation rate, since it maximized growth rates, with no effect on FCR. The higher CV_wt in the subsatiation group suggests increased competition for a restricted ration led to a slower growth with more growth variation. The decrease in growth in phases 2 and 3 was probably related to a high percentage of slower growing male fish in the population and the onset of sexual maturity. This study demonstrated that under commercial scale conditions, summer flounder can be successfully grown to a marketable size in a recirculating aquaculture system. Based on these results, it is recommended that a farmer feed at a satiation rate to minimize growout time. More research is needed to maintain high growth rates through marketable sizes through all‐female production and/or inhibition of sexual maturity.     

Evaluation of dietary protein and lipid requirements of two-banded seabream (Diplodus vulgaris) cultured in a recirculating aquaculture system

The objective of this study is to investigate the effects of dietary protein and lipid levels on the growth performance and bioeconomic benefits of two-banded seabream (Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experimental diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial body weight of ~3.64 g were reared in a recirculating aquaculture system and hand fed twice a day until satiation for a period of 60 days. In the experiment, no difference in survival rate was found between the different groups. Relative growth rate (RGR), specific growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not significantly affected by increasing protein and/or lipid treatments in this present study. However, the RGR, SGR and FCR values showed slightly better efficiency in the experimental group (35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with those fed other diets. According to bioeconomic analyses results, the diet with the 35 % protein and 15 % lipid generated the best profit. The results suggest that two-banded seabream can be accepted as a promising alternative species for the aquaculture industry and optimum growth of two-banded seabream fingerlings can be obtained when they are fed a diet containing 35 % crude protein and 15 % crude lipid.     

Effect of protein and lipid dietary levels on the growth of juvenile meagre (Argyrosomus regius)

This study investigates the effects of dietary lipid and protein levels in the growth, feed utilization and body composition of meagre (Argyrosomus regius). Triplicate groups of juvenile fish (23.4 ± 4.9 g average weight ± SD) were fed four isolipidic diets (17.5% crude lipids) containing 40, 45, 50 and 54% of protein, while in a separate experiment, fish (21.8 ± 3.7 g average weight ± SD) were fed four isonitrogenous (50% crude protein, dry matter) each containing 12, 15, 17 or 20% of crude lipids. In the protein requirement experiment, the increase in crude protein in the diet from 40 up to 50% positively affected SGR (Specific growth rate) and FCR (Feed conversion ratio). The increase in crude lipids in the diet from 12 up to 17% showed a tendency for improvement in SGR and FCR. In both experiments, the fastest growing fish exhibited higher lipid depots. Overall, the present investigation showed that juvenile meagre has an estimated protein requirement of 50% and it does not seem to require high dietary lipid levels.     

Growth,Feed Conversion,and Nutrient Retention Efficiency of African Catfish,Clarias gariepinus, (Burchell) Fingerling Fed Diets with Varying Levels of Protein

Growth, feed conversion, and nutrient retention efficiencies of African catfish fingerling, Clarias gariepinus (5.22 ± .07 cm; 8.22 ± 0.03 g), fed diets with varying levels of protein were assessed by feeding seven casein/gelatin based isocaloric (17.62 kJ/g GE) experimental diets with graded levels of dietary protein (20%, 25%, 30%, 35%, 40%, 45%, and 50% of the diet) to triplicate groups of fish to apparent satiation for eight weeks. Effects of feeding these diets on live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE%), and energy retention efficiency (ERE%) were assessed. Maximum LWG% (867%), PER (2.01), highest PRE (32%), ERE (69%), best FCR (1.39), and maximum body protein were recorded in fish fed diet containing 35% protein. On the basis of the second-degree polynomial regression analysis of the above response variables, it is recommended that the inclusion of protein in the range of 34.4%–39.6% is optimum for maximizing growth potential, feed conversion, and nutrient retention in African catfish fingerling, Clarias gariepinus.     

Effects of dietary protein levels on growth,feed utilization,protein retention efficiency and body composition of young <Emphasis Type="Italic">Heteropneustes fossilis</Emphasis> (Bloch)

An 8-week growth trial was conducted to assess the effect of dietary protein on growth, feed utilization, protein retention efficiency, and body composition of young Heteropneustes fossilis (10.02 ± 0.09 g; 9.93 ± 0.07 cm). Isocaloric (4.15 kcal g⁻¹, GE) diets with varying levels of protein (25, 30, 35, 40, 45, and 50% of the diet) were fed near to satiation to triplicate groups of fish. Optimum dietary protein was determined by analyzing live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR%), and protein retention efficiency (PRE%) data. Maximum LWG% (167), best FCR (1.42), PER (1.75), SGR (1.76), and PRE (31.7%) were evident in fish fed 40% protein diet (Diet 4). Body protein data also supported the above level. However, second-degree polynomial regression analysis of the above data indicated that inclusion of dietary protein in the range of 40–43% is optimum for the growth of young H. fossilis.     

Performance of murray cod, Maccullochella peelii peelii (Mitchell) in response to different feeding schedules

The Australian freshwater fish Murray cod, Maccullochella peelii peelii (Mitchell) is gaining popularity as a suitable species for intensive culture, particularly in closed systems. The aim of this study was to evaluate the performance of Murray cod in response to different feeding schedules. Growth, survival, food conversion and a range of other related parameters including carcass proximate composition were evaluated for fish in five feed management regimes. The feeding regimes used in the experiment were hand fed to satiation twice daily (SAT), a pre‐determined ration of 1.2% of the body weight day^?1 which was hand fed twice daily (HFR), and belt fed through the day only (B/D), belt fed through the night only (B/N) and belt fed for 24 h (B/DN). Each of the five feeding regimes was randomly allocated to three tanks (triplicates). All of the feeding regimes used a commercially prepared diet formulated specifically for Murray cod, containing ≈50% protein and ≈16% lipid. The experiment was conducted for 84 days. Specific growth rate ranged from 0.89±0.01 to 1.07±0.04% day^?1. Food conversion ratio (FCR) ranged from 1.09±0.02 to 0.92±0.03. The fastest growth and greatest final body weight were observed in the SAT treatment; however, the highest FCR, visceral fat index (VFI %) and hepatosomatic index (HSI %) were also observed in this treatment. Significant differences were found in specific growth rate and final mean weight between fish in the B/D and SAT treatments. B/N and B/DN feeding regimes appeared to result in the most favourable fish performance.     

The effect of light intensity on growth of juvenile dusky kob Argyrosomus japonicus (Temminck & Schlegel 1843)

South African juvenile dusky kob Argyrosomus japonicus are more abundant in turbid estuaries than in clear marine‐dominated estuaries. Turbidity can reduce light penetration into the water and create an environment different from that experienced by fish under culture conditions in mechanically filtered clear water. In order to optimize rearing conditions of this species, the effects of light intensity (23–315 lx) and feeding method (restricted ration vs. feeding to apparent satiation) on growth and food conversion ratio (FCR) of juvenile A. japonicus were assessed in a 56‐day growth trial. Fish weight increased from 7.2±1.6 to 41.9±10.2 g fish^?1 at a growth rate of 3.25% body weight day^?1. Light intensity did not significantly affect growth or FCR. Feeding method did not significantly affect growth rate, but average FCR was significantly better in treatments fed a ration of 3.6% body weight day^?1 than in treatments fed to apparent satiation. Therefore, a light intensity range of 23–315 lx can be used to culture dusky kob juveniles. The better FCR in fish fed a restricted ration suggests that a ration of 3.6% body mass day^?1 allowed good growth of juvenile dusky kob.     

Effect of feeding frequency on growth,feed efficiency and nutrient utilization of juvenile flounder (Platichthys flesus luscus)

An experiment was conducted to determine the effects of optimal feeding frequency on growth performance, feed efficiency, nutrient utilization and body composition in juvenile flounder. Four feeding frequencies of one (F1), two (F2), three (F3) and four (F4) times a day were evaluated as treatments in triplicate for a period of 60 days. Forty-seven hatchery produced juveniles (2.5 ± 0.7 g) were stocked into 160-L rectangular fiberglass tanks and fed with a commercial diet containing 54 % protein to satiation. At the end of the experiment, the final weight of F1, F2, F3 and F4 were 5.06 ± 0.29, 5.91 ± 0.42, 6.24 ± 0.42 and 6.16 ± 0.46 g, respectively. Growth rates and feed consumption were highest in F3 and lowest in F1. Feed conversion ratios ranged between 0.83 ± 0.04 and 0.90 ± 0.03. There were no significant differences in either moisture or ash content of the fish groups. Protein content decreased with increasing feeding frequency, while lipid content partly increased with increasing feeding frequency. Nitrogen intake and lipid intake were significantly higher in fish fed under F3 and F4 treatment, whereas the nitrogen gain decreased and lipid gain increased with increasing feeding frequency. It is concluded that the flounder juveniles can achieve maximum growth performance and better nutrient utilization when they are fed a given ration two times a day. The findings have practical significance toward establishing an appropriate flounder nursery rearing and will directly benefit the nursery operations.     

Determination of the optimal feeding rate and light regime conditions in juvenile burbot, Lota lota (L.), under intensive aquaculture

The aim of the study was to optimize burbot juveniles rearing in recirculating aquaculture system. In experiment 1 (17 °C, photoperiod 24L:0D), the fish (initial: body weight [W] = 15.36 ± 3.72 g, standard length [SL] = 12.48 ± 1.09 cm) were divided into four groups (I, II, III and IV). Different feeding levels were applied: 1, 2, 3 and 4 % of biomass daily (counted based on dry feed weight). The feed conversion ratio (FCR) and specific growth rate (SGR) were recorded. In experiment 2 (17 °C, feeding level of 2 % of biomass day^?1), fish (W = 5.24 ± 2.43 g and SL = 8.54 ± 1.24 cm) were divided into two groups where different light conditions were applied (I: 24 h light [1,800 lx] and II: 24 h darkness [4 lx]). In experiment 1, the highest SGR was recorded in group II (1.93 % day^?1), whereas the lowest SGR (1.27 % day^?1) and final W (P < 0.05) was in I group. The lowest (P < 0.05) FCR (0.63) was in group II. In the remaining groups, FCR was similar (0.68–0.70, P > 0.05). The feed consumption in group I reached 100 %, in group II, it was 71.3 % (P < 0.05) and it was the lowest in groups III (39.26 %) and IV (36.93 %). In experiment 2 no differences in the growth and survival rate were recorded (final SL between 14.16 and 14.19 cm, P > 0.05; W between 23.33–23.35 g; P > 0.05). The results from experiment 1 indicate that the feeding 2 % of biomass day^?1 was the most efficient. Also, it was proven, for the first time, that there was no effect of using different constant light conditions.     

The effect of dietary cricket meal (<Emphasis Type="Italic">Gryllus bimaculatus</Emphasis>) on growth performance,antioxidant enzyme activities,and haematological response of African catfish (<Emphasis Type="Italic">Clarias gariepinus</Emphasis>)

This study was conducted to investigate the growth performance, biomarkers of oxidative stress, catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST) as well as the haematological response of African catfish after being fed with fish feed containing different levels of cricket meal. The juvenile fish were assigned to three different treatments with isonitrogenous (35 %) and isoenergetic (19 kJ g^?1) diets containing 100 % cricket meal (100 % CM), 75 % cricket meal (75 % CM), and 100 % fishmeal (100 % FM) as control groups for 7 weeks. The results indicated that a diet containing 100 % CM and 75 % CM improved growth performance in terms of body weight gain and specific growth rate, when compared to 100 % FM. The feed conversion ratio (FCR) and protein efficiency ratio (PER) did not differ significantly between all diets, but reduced FCR and increased PER were observed with a higher inclusion of cricket meal. A haematological examination of fish demonstrated no significant difference of red blood cells in all diets and white blood cells showed a significantly higher value in fishmeal-fed fish. On the other hand, haemoglobin and haematocrit significantly increased with increasing amounts of cricket meal in the diet. Antioxidant activity of CAT was higher in the 100 % CM group compared to fish fed other diets, whereas GST and SOD showed increasing trends with a higher incorporation of cricket, although insignificant differences were observed between all diets. These results suggest that cricket meal could be an alternative to fishmeal as a protein source in the African catfish diet.     

Hybrid sturgeon ‘AL’ (Acipenser naccarii×Acipenser baeri) diets: the use of alternative plant protein sources

In this experimentation, corn gluten (CG) and pea meal (PM) were tested as potential protein sources in hybrid sturgeon ‘AL’. One hundred and twenty‐eight hybrid sturgeons ‘AL’ (Acipenser naccarii × Acipenser baeri) (initial body weight 364.8 ± 4.5 g) were utilized with four experimental diets and four replicates each; the experimental design was 4 × 4. Four isonitrogenous [crude protein=40% dry matter (DM)] and isoenergetic (gross energy=20 MJ kg^?1 DM) diets were formulated containing different levels of CG with or without PM and tested against a control diet that was fish meal (FM) based. Diets were as follows: CG55 contained 55% of corn gluten; diet CG55PM25 contained 55% CG and 25% PM; diet CG45PM25 contained 45% of corn meal and 25% of PM; and diet FM was control, based on FM. Fish fed with the PM diet showed lower values of feed conversion ratio (FCR) and specific growth rate (SGR) (FCR=4.53 ± 2.51 in the CG55PM25 diet; FCR=4.09 ± 1.45 in the CG45PM25 diet; SGR=0.20 ± 0.07 in the CG55PM25 diet; SGR=0.19 ± 0.11 in the CG55PM25 diet). The results of tissue proximate composition confirmed the results obtained from productive traits. This study indicates that CG meal but not PM could be utilized as a substitute of FM in hybrid sturgeon ‘AL’ nutrition.     

Growth and feed utilization of gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis>, L.) fed to satiation and restrictively at increasing dietary energy levels

Three isoproteic (47% protein) diets were formulated to contain graded levels of crude fat (diet D16:16%, diet D24: 24% and diet D32: 32%). Each diet was fed to satiation in three and to 80% satiation in two replicate groups of gilthead sea bream (Sparus aurata), having an initial body weight of 72–74 g. The trial lasted 81 days. Groups fed to satiation showed higher final body weight (FBW; 238.8–252.3 g vs. 218.0–229.3 g) and daily growth index (DGI; 2.49–2.65%/day vs. 2.27–2.34%/day) than those fed to 80% satiation. Feed intake was significantly different both for feeding level and for diet composition. Fish fed to satiation had higher feed conversion rate (FCR) compared to the 80% satiation groups (1.33–1.44 vs. 1.13–1.17; P ≤ 0.001). Within satiation groups, FCR was significantly lower in fish fed D16 compared to fish fed D32 (1.33 vs. 1.44, P ≤ 0.05), whereas no statistical differences were found within the 80% satiation groups. The increase in dietary lipid level did not improve growth performance, feed efficiency and protein utilization but decreased gross lipid efficiency. Conversely, a reduction in ration from satiation to 80% satiation decreased DGI, thus improving FCR. Feed costs were influenced by dietary energy level and feeding ratio, the lowest energy diet at 80% satiation being the most profitable combination among the variables.     

Additional feeding of vitamin–mineral‐based nutraceutical to stress‐exposed rohu,Labeo rohita,enhances the IGF‐1 gene expression and growth

One thousand and eighty rohu fingerlings with an average size of 8.5 ± 0.5 g were randomly distributed in 6 distinct experimental groups in triplicates, where the first three groups were exposed to high stocking density (HSD; 20 nos/ 75 L water) with restricted feeding (RF), viz. THR0 (HSD, RF, 0% nutraceutical), THR1 (HSD, RF, 0.1% nutraceutical) and THR5 (HSD, RF, 0.5% nutraceutical), and second three groups were exposed to normal stocking density (NSD; 10 nos /75 L water) with satiation feeding (SF) and designated as TNS0 (NSD, SF, 0% nutraceutical), TNS1 (NSD, SF, 0.1% nutraceutical) and TNS5 (NSD, SF, 0.5% nutraceutical). The weight gain (WG) %, specific growth rate (SGR), protein efficiency ratio (PER) and IGF‐1 expression were significantly lower, whereas feed conversion ratio (FCR), serum superoxide dismutase (SOD) and catalase activities were significantly higher in fish exposed to HSD with RF at monthly sampling. Feeding of 0.1% dietary nutraceutical resulted in a significantly higher WG%, SGR, PER and IGF‐1 expression and lower FCR, SOD and catalase activities at the end of the third and fourth month of feeding in HSD with RF groups. The present study concluded that 3‐month feeding of 0.1% nutraceutical could improve growth and reduce stress in fish.     

Dietary lysine requirement of fingerling Catla catla (Hamilton) based on growth, protein deposition, lysine retention efficiency, RNA/DNA ratio and carcass composition

A 12-week experiment was conducted to quantify dietary lysine requirement of fingerling Catla catla (3.65 ± 0.05 cm; 0.58 ± 0.02 g) by feeding casein–gelatine-based diets (33.0 % crude protein; 14.3 kJ/g digestible energy) with six levels of l-lysine (1.25, 1.50, 1.75, 2.00, 2.25 and 2.50 % dry diet). The experiment was conducted in eighteen 70-L indoor polyvinyl circular troughs provided with a water flow-through system (1–1.5 L/min). Live weight gain (LWG), feed conversion ratio (FCR), protein deposition (PD), lysine retention efficiency (LRE%) and RNA/DNA ratio were used as the response criteria. Second-degree polynomial regression analysis at 95 % maximum and minimum response of LWG and FCR data exhibited the lysine requirement between 1.8 and 1.9 % dry diet, corresponding to 5.5–5.7 % dietary protein. Regression analysis of PD, LRE and RNA/DNA ratio yielded the requirement between 1.7 and 1.8 % dry diet, corresponding to 5.2–5.5 % dietary protein. Since live weight gain and protein deposition are the key parameters for estimating nutrient requirement, these tools were used to recommend the lysine requirement of fingerling C. catla which ranges between 1.7 and 1.8 % dry diet. Data generated during this study will be useful to formulate lysine-balanced feed for intensive culture of this fish.     

不同饲料蛋白水平下点带石斑鱼对鸡肉粉、羽毛粉和血粉混合物的利用能力

通过10周网箱养殖实验,评价了不同饲料蛋白水平下点带石斑鱼对1种鸡肉粉、羽毛粉和血粉混合物的利用能力。采用2×4实验设计,设2个饲料蛋白水平(490 g/kg和530 g/kg粗蛋白),每个饲料蛋白水平下设4个鱼粉水平,其中1组饲料中加入500 g/kg鱼粉(对照),另外3组饲料中分别加入139、278、416 g/kg的鸡肉粉、羽毛粉和血粉混合物(鸡肉粉∶羽毛粉∶血粉=65∶20∶15)替代对照饲料中30%、60%、90%的鱼粉。实验鱼初始体重为(33.4±0.1) g。实验期间,除恶劣天气外,每天分两次按饱食量投喂实验鱼。实验结果表明,饲料蛋白水平对摄食量、增重,饲料系数、氮储积效率、能量储积效率和鱼体组成无显著影响;饲料鱼粉含量显著影响增重,饲料系数、氮储积效率和能量储积效率,但对摄食量和鱼体组成无显著影响。在相同饲料蛋白水平下,特定生长率(SGR)随鱼粉含量降低而下降;当鱼粉含量相同时,摄食高蛋白饲料的鱼SGR略高于摄食低蛋白饲料的鱼。本实验结果显示,通过添加鸡肉粉、羽毛粉和血粉混合物可将点带石斑鱼饲料鱼粉含量降低到200 g/kg,在490~530 g/kg范围内提高饲料蛋白水平无助于降低点带石斑鱼饲料鱼粉含量。     

Nutritional evaluation of autoclaved Salicornia bigelovii Torr. seed meal supplemented with varying levels of cholesterol on growth, nutrient utilization and survival of the Nile tilapia (Oreochromis niloticus)

A 7-week feeding trial was conducted to investigate the effects of replacing fish meal by autoclaved Salicornia bigelovii seed meal (SSM), supplemented with varying cholesterol levels, on feed intake, growth performance, body composition and survival of Nile tilapia Oreochromis niloticus fingerlings under laboratory conditions. SSM was tested at different inclusion levels (0, 25, 50 and 65 % of total protein), using different levels of cholesterol supplementation (0, 1, 2 and 2.6 %) in isonitrogenous (420 g Kg^?1 DM crude protein) and isocaloric (18.52 MJ Kg^?1 DM) fish meal–Soybean meal-based diets. Triplicate groups of fish (374 ± 15 mg, initial fresh body weight) were randomly stocked in 18 20-L plastic tanks at a stocking density of 20 fish per tank and were fed to satiation by hand five times a day, 7 days per week. Feed intake, growth performance and survival were significantly affected by the SSM inclusion level and the cholesterol supplementation. The lower growth performance of fish fed diets containing SSM without cholesterol is thought to result from the presence of saponins in the meal. When cholesterol is added, the saponin-induced toxicity is ameliorated, which is evident from growth and survival responses, up to 50 % of SSM protein inclusion. At the highest level of SSM inclusion (65 %), growth and survival were very poor, despite the addition of cholesterol. The results of the present work suggest that autoclaved SSM can partially substitute fish protein in diets for O. niloticus fingerlings at levels up to 50 % of the dietary protein if 2 % cholesterol is added in fish meal–SBM-based diets.     

Effects of safflower oil supplementation in diet on growth performance and body fatty acid composition of turbot (Psetta maxima)

The aim of the study was to investigate the effects of the diets that contain safflower oil and fish oil as lipid sources, on growth, feed conversion and body composition in turbot (Psetta maxima). Two iso-nitrogenous and iso-lipidic diets (55 % protein and 14 % lipid) were prepared that include 100 % fish oil (FO group) and 100 % safflower oil (SFO group) for turbots with average weight of 62.21 ± 1.28 g, and fish were fed with these diets for 104 days. At the end of the experiment, the weight gain, specific growth rate and feed conversion ratio were the highest in SFO group than in FO group (p < 0.05). Fatty acid composition of fish body reflected the fatty acid composition determined in the experimental diets. The amounts of palmitic acid (PA; C16:0), oleic acid (OA; C18:1n-9), linoleic acid (LA; C18:2n-6) and docosahexaenoic acid (DHA; C22:6n-3) were dominant fatty acids in fish body. It was confirmed that the usage of safflower oil instead of fish oil in turbot feed did not generate any negative effects on growth, feed conversion and the values regarding the growth performance.