Effect of Dietary Lipid Level and Feeding Frequency on the Growth,Feed Utilization,and Body Composition of Juvenile Spotted Seabass,Lateolabrax maculatus

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.     

Relationship Between Dietary Protein Source and Feeding Frequency During Feeding Nile Tilapia,Oreochromis niloticus (L.) Cultured in Concrete Tanks

ABSTRACT

A 24-week feeding trial was conducted in concrete tanks with Nile tilapia, Oreochromis niloticus (L.) with an average initial weight and length of 50.87 ± 6.03 g and 14.4 ± 0.45 cm, respectively, to examine the effect of two protein sources and two feeding frequencies on growth performance, production traits, and body composition. Twelve 4 m³ concrete tanks (2 × 2 × 1.25 m, long, width, and height) were each stocked with 100 fish and fed diets containing either fish meal protein or soybean meal protein at two feeding frequency of two times daily or four times daily (2 × 2 × 3 factorial experiment). The results revealed that there was no significant effect of dietary protein sources on growth rate, whereas there was a significant increase in growth rate with increasing feeding frequency (P < 0.05). The same trend was also observed for mean body weight (g), production rate (kg/m3), specific growth rate (SGR % day^?1). The best final mean body weight (g), specific growth rate (SGR % day^?1), and production rate (kg/m3) were recorded in groups of fish fed with feeding frequency four times daily. Whole fish moisture, protein, fat, and ash contents were significantly influenced (P ≤ 0.05) by protein sources and feeding frequency, except protein not influenced with feeding frequency. Energy was significantly (P < 0.05) influenced by feeding frequency, but not by dietary protein sources. Economic evaluation indicated that soybean meal (Diet B) at four times feeding daily was the most cost-effective and affordable feed strategy for farmers. We conclude that a soybean diet fed four times daily is recommended for adult Nile tilapia reared in concrete tanks.     

投喂频率对尼罗系吉富罗非鱼幼鱼胃排空、生长性能和体组成的影响

通过胃排空试验与养殖试验研究了不同投喂频率对尼罗系吉富罗非鱼幼鱼的胃排空、生长性能以及体组成的影响.在试验开始时,观测尼罗系吉富罗非鱼幼鱼的胃内饲料排空情况,胃排空试验结果表明,胃排空率的最佳描述为平方根函数,胃内饲料在饱食投喂后15 h左右完全排空,达到投喂前水平,80％胃排空为9h,也就是投喂后大约9h恢复食欲.360尾试验鱼(初始体质量3.72 g)以不同的投喂频率(1d4次、1d3次、1d2次、2d4次、2d3次、2d2次)分组,每组设立3个平行组,随机养殖于18个网箱中,每箱养殖20尾鱼,按饱食量投饲膨化饲料.养殖期为6周.尼罗系吉富罗非鱼幼鱼在投喂频率为1d4次、1d3次和1d2次时特定生长率和饲料效率显著高于投喂频率为2d4次、2d3次和2d2次时(P＜0.05)；投喂频率为1d2次、2d4次、2d3次和2d2次时其摄食量显著低于1d4次和1d3次时(P＜0.05).随着投喂频率降低,鱼体水分含量逐步上升,脂肪和蛋白质含量逐步下降,其中1d4次、1d3次组鱼与2d2次组鱼有显著性差异(P＜0.05).各投喂频率组间的肝体指数无显著性差异(P＞0.05).3.7～48.0 g尼罗系吉富罗非鱼幼鱼的适宜投喂频率为1d2次,较2d2次、2d3次和2d4次时明显提高了生长速度和饲料效率,较1d3次、1d4次摄食量显著降低.2种试验结果较为一致.     

饲料蛋白质水平与投喂频率对吉富罗非鱼幼鱼生长及部分生理生化指标的影响

为探讨饲料蛋白质水平与投喂频率对罗非鱼生长及生理健康的影响,采用2×3双因子实验,研究饲料蛋白质水平(36.27%和26.02%)与投喂频率(1、2和3次/d)对吉富罗非鱼幼鱼生长、体成分、血清指标和肝胰脏结构的影响。养殖周期为42 d,结果表明:随饲料蛋白质水平的增加,实验鱼的末体质量(FW)、增重率(WGR)、特定生长率(SGR)、饲料效率(FE)、肥满度(CF)、去内脏全鱼灰分(EWA)、内脏水分(VM)、高密度脂蛋白胆固醇(HDLC)水平显著升高(P0.05),而摄食率(FI)、脏体比(VSI)、饲料成本(FC)、去内脏全鱼粗脂肪(EWF)、内脏粗脂肪(VF)、肝胰脏粗脂肪(HF)显著降低(P0.05);随投喂频率的增加,实验鱼的FW、WGR、SGR、肝体比(HSI)、CF、FC、EWF、VF、HF,血清中的总胆固醇水平(TCHO)、HDLC、低密度脂蛋白胆固醇(LDLC)、总蛋白(TP)、甘油三酯(TGK)水平显著升高(P0.05),而FE、蛋白质效率(PER)、去内脏全鱼水分(EWM)、EWA、VM、肝胰脏水分(HM)显著降低(P0.05)。饲料蛋白质水平和投喂频率对实验鱼的FW、WGR、SGR、VM和HDLC的交互作用显著(P0.05)。投喂26.02%蛋白质水平饲料的实验鱼,肝胰脏细胞肿大变形,呈现透明的空泡化,出现细胞核偏移;而投喂36.27%蛋白质饲料的实验鱼,大多数肝细胞胞浆清晰,可观察到的肝细胞空泡面积较小。综合考虑,饲料蛋白质含量为36.27%是适合吉富罗非鱼幼鱼的,其适宜的投喂频率为2次/d以上,可根据罗非鱼市场情况进行调节。     

Effect of partial replacement of fish meal with soybean meal and feeding frequency on growth,feed utilization and body composition of juvenile Chinese sucker,Myxocyprinus asiaticus (Bleeker)

A factorial (2 × 4) feeding trial was conducted to investigate the effects of feeding frequency and partial replacement of fish meal (FM) with soybean meal (SBM) on the growth performance, feed utilization and body proximate composition of juvenile Chinese sucker. Two feed types including replacement of 30% FM (diet 1) with SBM (diet 2) were used. Triplicate groups of fish (average weight, 11.80 ± 0.19 g) were fed each feed type to visual satiation at four meals per day, three meals per day, two meals per day and one meal per day for 8 weeks. At the end of the feeding trial, the survival of fish was not significantly different among the treatments. Weight gain was affected by the feeding frequency. The highest weight gain was observed in fish fed with diet 1 at three meals per day. There existed a significant difference in daily feed intake (DFI), daily protein intake (DPI), feed conversion ratio (FCR) and protein efficiency ratio (PER) when the feeding frequency was increased from one or two to three or four meals per day (P < 0.001), but not by the feed types. For both two feed types, the highest DFI and DPI were observed at three meals per day. The highest PER was gained at four meals per day, while FCR was the least. The body proximate composition of fish was altered by feeding frequency. The crude lipid content increased with the increase in feeding frequency. Essential amino acids (EAAs) content showed no significant differences among different treatments. The present findings suggest that three feedings per day at visual satiation may be sufficient for the maximal growth performance of Chinese sucker grown from 11 to 45 g. Results also indicate that about 30% of FM protein can be replaced by SBM protein in Chinese sucker diets without adversely affecting growth.     

Effects of feeding frequency on food intake,growth and body composition of rainbow trout (Salmo gairdneri)

The effects of feeding frequency on food intake, weight change and relative proportions of the major body components were investigated at 10°C in a strain of hatchery-reared rainbow trout. Feeding frequencies were from one meal every second day to six meals per day, within the range common to current piscicultural techniques. Fish were fed a dry, pelleted diet either to satiation at each meal, or in restricted total daily amounts based on a percentage of their wet body weight. All fish were forced to swim at a constant speed of approximately one body length per second to minimize variability in growth and body composition.Maximum daily food intake occurred with just two feedings to satiation per day. Growth closely paralleled food intake. Neither specific growth rate nor whole body levels of moisture, lipid or protein were affected significantly by differences in feeding frequency. A trend towards increased body fat with more frequent feeding was observed among fish fed to satiation at each meal; this was believed to be the result of a somewhat higher total food intake than among less frequently fed fish. Fish fed a restricted daily ration divided into a number of meals exhibited smaller differences in lipid content.The general lack of response to feeding frequency was attributed primarily to the low metabolic rate of trout and to the characteristically slow rate of food passage in the digestive tract.     

Effects of feeding frequency and feed type on the growth,feed utilization and body composition of juvenile olive flounder,Paralichthys olivaceus

A factorial (3 × 4) feeding trial was conducted to investigate the effects of feeding frequency and feed type on the growth performance, feed utilization and body proximate composition of juvenile olive flounder. Three feed types including a sinking moist pellet (MP), a sinking dry pellet (DP) and a floating extruded pellet (EP) were used. Fish (average weight, 11.1 ± 0.4 g) were randomly distributed in thirty‐six 300 L tanks in a flowthrough system. Triplicate groups (30 fish per tank) of fish were fed each feed type to visual satiation at three meals per day, two meals per day, one meal per day and one meal every 2 days for 7 weeks. At the end of the feeding trial, the survival of fish was not significantly different among the treatments. Weight gain was affected by the feeding frequency. The highest weight gain was observed in fish fed the EP at three meals per day. The daily feed intake of fish fed the MP and DP tended to be higher than that of fish fed the EP at each feeding frequency. The feed efficiency and the protein efficiency ratio of fish fed the EP were higher than those of fish fed the MP and DP. The body proximate composition of fish was altered by the feeding frequency. The crude lipid content increased with the increase in the feeding frequency. The present findings suggest that three feedings per day at visual satiation of the floating EP may be sufficient for the maximal growth performance of olive flounder grown from 11 to 60 g.     

Effect of feeding frequency on growth,feed utilization,body composition and waste output of juvenile golden pompano (Trachinotus ovatus) reared in net pens

A 6‐week feeding trial was conducted to examine the effect of feeding frequency on growth, feed utilization efficiency, body composition and waste output of juvenile golden pompano Trachinotus ovatus reared in net pens. Fish (10.3 ± 0.5 g) were either fed a formulated diet containing 48.4% crude protein and 5.7% crude lipid at 0.5, 1, 2, 3 or 4 meals per day or fed a raw fish feed at two meals per day as a control. The weight gain (WG) increased with increasing feeding frequency from 0.5 to 3 meals per day (P < 0.05), but did not significantly change with the further increase in feeding frequency from 3 to 4 meals per day (P > 0.05). The feed intake (FI) was lower in fish fed at 0.5 or 1 meal per day than in fish fed at 2, 3 or 4 meals per day (P < 0.05). No significant differences were found in the feed conversion ratio (FCR), nitrogen retention efficiency (NRE), condition factor (CF), nitrogen waste output (NWO) and phosphorus waste output (PWO) between fish fed at 1, 2, 3 or 4 meals per day (P > 0.05), whereas no significant difference was found in the phosphorus retention efficiency (PRE) among the feeding treatments (P > 0.05). The body lipid content increased, whereas the contents of moisture and ash decreased, with the increase in feeding frequency (P < 0.05). At the same feeding frequency, fish fed the formulated diet exhibited lower FI, FCR, HSI, body moisture content, NWO and PWO, but higher NRE, PRE, body lipid content and body phosphorus content than those of fish fed the raw fish feed (P < 0.05). These results suggest that the formulated diet can satisfy nutrient requirements of juvenile golden pompano reared in net pens, and the suitable feeding frequency is 3 meals per day.     

Response of African Catfish, Clarias gariepinus (Burchell, 1822), to Diets of Pigeon Pea, Cajanus cajan, Subjected to Different Processing Methods

Raw undehulled pigeon pea, Cajanus cajan, seeds were processed by toasting, boiling, and soaking before milling to produce pigeon pea meals (PPMs). African catfish, Clarias gariepinus, were fed eight diets formulated with these meals at two dietary inclusion levels of 600 and 650 g/kg in combination with fish waste meal levels of 350 and 330 g/kg, respectively, to yield a protein and energy contents of 35.96 ± 2.1% dry matter and 18.04 ± 0.2 kJ/g. Fish (mean weight 0.46 g) were weighed and distributed to 24 experimental tanks (seven fish per tank). Triplicate fish groups were fed restricted ration (5% of biomass) per day in two portions for 56 d in static water. Results showed that fish groups fed raw PPM diets had low body weight gain (BWG), inferior specific growth rate (SGR), and high feed conversion ratio (FCR) when compared to other feeding groups. The hematocrit, hemoglobin concentration, and red blood cell and white blood cell counts decreased significantly (P < 0.05) with raw PPM diets. Slight decrease also was recorded among groups fed diets of other processing methods when compared with initial fish. However, soaking for 16 h enhanced best fish BWG, SGR, FCR, and hematological values and can be recommended as a good processing method of PPM for African catfish diets.     

Dietary Protein Level and Feeding Rate for Hybrid Clariid Catfish,Clarias gariepinus X Heterobranchus bidorsalis,in Homestead Tanks

Abstract

A 3 × 3 factorial experiment was designed to determine the effects of protein levels and feeding rate on growth and body composition of hybrid clariid catfish, Clarias gariepinusX Heterobranchus bidorsalis, over 12 weeks experimental period. Hybrid catfish (initial mean weight 12.53±0.35 g) were stocked in three feeding rates (3%, 5%, or 7% body weight/day (bw/day) and three crude protein levels (30%, 35%, or 40%). Each treatment was assigned randomly to three tanks. Final weight was higher for fish fed at 40% than those fed at 30% and 35% CP. There was no significant difference (P >0.05) in fish fed at 3%, 5%, and 7% bw/day. Also, there was no significant interaction between feeding rate and dietary protein level for weight gain, specific growth rate or feed conversion ratio. Weight gain and feed efficiency under feeding rates increased linearly as protein level increased. Dietary protein levels and feeding rate had significant effect on fish survival. Protein levels had a positive linear effect on fish body protein in all the feeding rates. Based on the above results, 40% CP level and 5% bw/day feeding rate are suggested to be optimal for achieving optimum growth rate and body composition.     

Partial substitution of fish meal with soybean and cottonseed meals in diets for African bonytongue,Heterotis niloticus (Cuvier, 1829) fingerlings: effects on growth,feed efficiency and body composition

A feeding trial was conducted to examine the suitability of soybean meal (SBM) and cottonseed meal (CSM) as a partial substitute for the dietary protein supplied by fish meal for H. niloticus fingerlings. Fish were fed with four isonitrogenous (350 g kg^?1 crude protein) and isoenergetic (18.8 kJ g^?1 GE) diets in which fish meal protein was gradually replaced by plant protein from a mixture of SBM and CSM (0%, 25%, 50% and 75% in diets 1, 2, 3 and 4 respectively). Triplicate groups of fingerlings H. niloticus (mean weight of 5 g) were handfed twice daily to apparent satiation for 60 days inside net hapas. Growth performances (SGR varied from 3.09% to 3.16% day^?1) of fingerlings fed diets containing 0%, 25% and 50% plant protein were not significantly different (P>0.05). At 75% fish meal substitution, growth and feed utilization efficiency indicators were significantly reduced (P<0.05). The carcass composition were also significantly (P<0.05) affected by the replacement level of fish meal, except dry matter and ash. Results suggest that the dietary fish meal protein could efficiently be substituted by a mixture of soybean and cottonseed meals up to 50%, without adverse effects on maximal growth in practical diets for H. niloticus fingerlings.     

Optimization of Feeding Rate for Hatchery-Produced Juvenile Gilthead Sea Bream Sparus aurata

Abstract.— A 61-d growth trial (five 11-d feeding periods) was conducted to determine the effects of feeding rate on growth, feed utilization, morphology, and body composition of the gilthead sea bream Sparus aurata . Gilthead sea bream juveniles with an average initial body weight of 3 g were fed a commercial diet (51% crude protein, 11% crude fat) at rates of 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0% of their body weight (BW) per day in two equal meals. Water temperature was approximately 21.4 C throughout the experiment. Each ration was administered to triplicate groups of 60 fish, with ration readjusted every 11 d. Growth rate was measured as specific growth rate (SGR). Survival rate and coefficient of variation did not differ significantly among the groups fed different rates. Body weight, condition factor, and hepatosomatic and viscerosomat-ic indices displayed significant increases with increasing feeding rate from 0.5 to 3.0% BW/d. Fish fed 0.5% BW/d had significantly higher moisture and ash and lower protein contents than those fed at higher rates. Moisture and protein contents were not significantly different for fish fed at the highest feeding rates (2.0, 2.5, and 3.0% BW/d). Lipid contents increased significantly with increasing feeding rate from 0.5 to 3.0% BW/d. The SGR showed a curvilinear significant increase when the feeding rate was increased from 0.5 to 3.0% BW/d. Feed efficiency (FE) increased significantly to a maximum value with increasing feeding rate from 0.5 to 2.0% BW/d and decreased significantly with increasing feeding rate from 2.5 to 3.0% BW/d. Based on the data obtained, feeding rates of 2.3% and 0.6% BW/d are recommended as optimum and maintenance rations, respectively.     

Evaluation of growth, feed utilization, and economics of hybrid tilapia, Oreochromis niloticus×Oreochromis aureus, fed diets containing different protein sources in combination with distillers dried grains with solubles

A feeding trial was conducted in aquaria with juvenile hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) to evaluate the use of different protein sources in combination with distillers dried grains with solubles (DDGS). Twelve 110‐L glass aquaria were stocked with 28 juvenile (2.7±0.5‐g) hybrid tilapia per aquarium. Three replicate aquaria were randomly assigned to each of the four dietary treatments. Diets were isonitrogenous and isocaloric. The control diet contained 12% fish meal and 41% soybean meal as the primary protein sources (Diet 1). Each experimental diet contained 30% DDGS by weight, in combination with 8% fish meal and 34% soybean meal (Diet 2), 26% meat and bone meal (MBM), and 16% soybean meal (Diet 3), or 46% soybean meal alone (Diet 4). Fish were fed to apparent satiation twice a day for 10 weeks. There were no significant differences (P>0.05) in average weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) among tilapia fed Diets 1, 2, and 3. Fish fed Diet 4 had significantly lower (P<0.05) average weight gain, SGR, and PER than fish fed Diets 1 and 3. Relative cost per unit weight gain for Diets 1, 2, and 3 were statistically similar (P>0.05), while cost per unit weight gain for Diet 4 was significantly higher (P<0.05) than other diets. Diet 3 represented approximately a 20% cost savings compared with the control diet, with no reduction in growth. This study indicates that diets without fish meal containing 30% DDGS in combination with MBM and soybean meal provide good growth in tilapia. A diet without animal protein did not support acceptable growth.     

Fisheries by-catch and processing waste meals as ingredients in diets for Nile tilapia, Oreochromis niloticus

Digestibility, feeding and growth studies were conducted with Nile tilapia using diets containing fishery by‐catch and processing waste meals. Three meals manufactured from sorted fisheries by‐catch (MBM, from mixed benthic species, SPM, from small pelagic species, CAM, from mixed catfish species) one from tuna cannery waste (TCW) and one commercial anchovy meal (COM) were tested. By‐catch and processing waste meals had lower protein, lower lipid and higher ash contents than anchovy meal. The meals were all highly digestible and no significant differences (P≥0.05) were observed between apparent protein digestibility measurements. Five feeds, containing fish meal as the major protein ingredient, were formulated and fed to triplicate groups of 30 juvenile tilapias for 9 weeks. Survival, weight gain, specific growth rate (SGR), feed conversion ratio, protein efficiency ratio, phosphorus retention and whole body proximate composition were compared. Weight gain and SGRs were similar for each treatment group and compared favourably with the results obtained from juvenile tilapia elsewhere. Growth was the highest for CAM (P≤0.05), which contained both the highest essential amino acid levels and the highest ash content. Phosphorus retention was significantly lower in fish fed with high ash meals, MBM, CAM and TCW (P≤0.05) than in fish fed with the lower ash meals COM and SPM. Overall, the fisheries by‐catch and processing waste meals evaluated in this study are suitable protein ingredients for juvenile tilapia feeds.     

Effects of Dietary Energy Level and Number of Meals on Growth and Body Composition of Nile Tilapia Oreochromis niloticus (L.) During Summer and Winter Seasons

Two feeding trials (experiments 1 and 2) were conducted to determine the combined effect of dietary energy levels (low energy, LE and high energy, HE) and number of daily meals (one meal with the entire daily amount, two meals with half of the daily amount, and three meals with one‐third of the daily amount) on the growth and body composition of Nile tilapia Oreochromis niloticus in a recirculating system at different water temperatures, representing winter and summer seasons. In experiment 1 (winter), weight gain and specific growth rate (SGR) were significantly (P < 0.05) affected by dietary energy levels, but not by number of meals. Weight gain and SGR for fish fed the LE diet one daily meal were significantly (P < 0.05) higher than for fish fed the HE diet in one daily meal. Feed efficiency ratio (FER) and energy efficiency ratio (EER) were significantly (P < 0.05) affected by dietary energy levels, but not by number of meals. Protein efficiency ratio (PER) was not significantly (P > 0.05) affected by either dietary energy levels or number of meals. However, protein retention was significantly (P < 0.05) affected by both dietary energy levels and number of meals. The chemical composition (moisture, protein, lipid, and ash) of fish muscle was not significantly (P > 0.05) affected by either dietary energy levels or number of meals. However, visceral fat content was significantly (P < 0.05) affected by dietary energy levels, but not by number of meals. In experiment 2 (summer), weight gain and SGR were significantly (P < 0.05) affected by number of meals, but not by dietary energy levels. Weight gain and SGR for fish fed the LE and HE diets in two daily meals were significantly (P < 0.05) higher than those fed one daily meal. FER and PER were significantly (P < 0.05) affected by number of meals, but not by dietary energy levels. The highest FER and PER were observed in fish fed two daily meals. EER was significantly (P < 0.05) affected by both dietary energy levels and number of meals. Moisture and protein content of the whole fish were not significantly (P > 0.05) affected by either dietary energy levels or number of meals. Lipid content was significantly (P < 0.05) affected by dietary energy levels, but not by number of meals. Based on the results of these experiments, Nile tilapia should not be fed high‐energy diets to improve fish performance even under a limited feed allowance during winter or summer. Fish grew rapidly when fed two daily meals during summer, but number of meals had no effect on fish performance during winter.     

Effect of feeding time and frequency on the growth and feed utilization of African catfish Clarias gariepinus (Burchell 1822) fingerlings

The effects of feeding time and frequency on the growth, feed utilization and survival of Clarias gariepinus (Burchell 1822; family Clariidae) fingerlings were evaluated in a 25-day study. Groups of African catfish with an initial individual weight of 0.98 ± 0.02 g were offered feeds continuously for 24 h, or during the day or night at different time intervals, with varying meal size. The growth rate was significantly affected by meal times. Widely practised day time feeding with three equal size meals a day gave the lowest growth and highest food wastage. The growth rates of fish fed continuously or during night time following their feed demand were significantly higher with lowest food conversion ratios and food wastage.     

The influence of feeding rate on growth, feed efficiency and body composition of juvenile grass carp (Ctenopharyngodon idella)

An 8 weeks growth study was conducted to estimate the optimal feeding rate for juvenile grass carp (3.08±0.03 g, mean ± SD). Fish were fed with a casein purified diet (360 g protein, 56 g lipid and 3000 kcal total energy/kg dry diet) at six feeding rates: 1.0, 1.5, 2.0, 2.5, 3.0, 3.5% body weight per day (BW d⁻¹). Each feeding rate was randomly assigned to three tanks of fish with 30 fish per tank (50W × 50H × 100L, cm). Fish were maintained in recirculating systems at a water temperature of 24.97±2.23 °C and were fed four times per day. After 2 weeks, fish fed on 3.5% BW d⁻¹ could not finish the diet and this treatment was cut-off. Analysis of variance showed that growth performance was significantly (p<0.05) affected by different feeding rates. The nutrient compositions of whole body, muscle and liver were also significantly different among treatments. The body weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER), apparent digestibility coefficiency (ADC), retention of protein (PR), mesenteric fat index, body moisture and protein content were significantly (p<0.05) affected by feeding rate. The WG, SGR and digestion rate were highest at 2% BW d⁻¹, although the FE and PER decreased with increasing feeding rate. Broken line analysis on specific growth rate indicated that the optimum feeding rate of juvenile grass carp is 1.97% body weight day⁻¹.     

Effects of handling, discrete meals and body weight on the individual variation of gastric emptying parameters

Individual feeding and gastric emptying was estimated for two salmonid species, brown trout (bt), Salmo trutta (L.), and rainbow trout (rt), Oncorhynchus mykiss (Walbaum), fed extruded feed with glass beads, and exposed to repetitive handling, anaesthetizing and X-raying. No significant effect was found to be caused by the handling and experimental procedures. Huge inter-individual (bt: CV_g= 52-104%; rt: CV_g= 19-33%) differences in discrete meal size were caused by interspecific differences in feeding behavior. An exponential model was fitted to the X-ray time series data for each individual for a computation of the initial (Ri) and fractional (R) gastric emptying rates. The individual variations in meal size had no significant effect on the rates. The meal frequency [two meals per day versus postprandial starvation (PS)] significantly affected the fractional gastric emptying rate. The rate decreased significantly for the PS groups while the inter-individual variation increased. Body weight (10-2500 g) significantly affected the fractional gastric emptying rates, which increased by up to 600 g and then decreased. The coefficient of variation for R increased with body weight. An equation for calculation of weight specific food processing rate (FP) is proposed. The FP decreased significantly with body weight. A maximum estimate of FP_i= 2.3 mg g^?1 h^?1 at 12°C for an individual was obtained with a 13.7-g trout. An increased weight-specific consumption (per cent body weight) for the smallest fish demonstrated that FP_g was 5.4 times higher than for the biggest fish, but after normalization with a body weight exponent of 0.75, an estimate of 1.7-2.3 was obtained.     

利用豆粕、菜粕和棉粕替代饲料中鱼粉对苏氏圆腹鱼芒摄食、生长和饲料利用的影响

摘要：通过8周网箱实验评价了利用豆粕、菜粕和棉粕作为苏氏圆腹鱼芒 （Pangasius sutchi）饲料中鱼粉替代蛋白源的潜力。配制了7种等氮、等能饲料，其中基础饲料含45%鱼粉，按等量蛋白替代的原则，在其余6种饲料中分别添加31%和46%豆粕替代基础饲料中鱼粉的50%和75%，或添加20%和40%菜粕替代基础饲料中鱼粉的25%和50%，或添加19%和39%棉粕替代基础饲料中鱼粉的25%和50%。实验中所用的苏氏圆腹鱼芒初始体重为11.3 g。实验结果表明：添加豆粕将饲料中鱼粉含量从45%降低到23%，添加菜粕或棉粕将鱼粉含量降低到34%，对鱼成活率、摄食、鱼体增重、特定生长率（SGR）、饲料系数（FCR）、饲料蛋白储积率、脏体指数和红血细胞比积（Hct）未产生显著不良影响。添加豆粕将鱼粉含量降低到11%导致鱼摄食、鱼体增重和SGR下降，添加菜粕将鱼粉含量降低到23%导致FCR和鱼体能量储积率下降，添加棉粕将鱼粉含量降低到23%导致鱼体增重、SGR和Hct明显下降。上述结果显示，可通过添加豆粕（31%）将苏氏圆腹鱼芒 鱼种饲料中鱼粉含量降低到23%，或通过添加菜粕（20%）和棉粕（19%）将饲料中鱼粉含量降低到34%。     

投喂频率对斑点叉尾鮰幼鱼生长、饲料利用和鱼体组成的影响

通过8周的生长试验,研究斑点叉尾鮰(Ictalurus punctatus)幼鱼(初始体重约4.5 g)的最适投喂频率。试验饲料为自制配合饲料,粗蛋白38%,总能19.0 kJ/g。设计了1～5次/d(M1-M5)5种投喂频率。结果表明:M2、M3、M4组摄食率均显著高于M1和M5组(P<0.05),其中M4组最大。M3、M4、M5组的特定生长率均显著高于M1组(P<0.05),其中M3组最大。M2、M3、M4、M5组的干物质表观消化率均显著高于M1组(P<0.05),M3和M4组的蛋白和能量表观消化率均显著高于M1和M2组(P<0.05)。M3组干物质含量显著高于M1和M2组(P<0.05),M2、M3、M4和M5组的粗蛋白、粗脂肪和能量含量均显著高于M1组(P<0.05)。因此,本研究建议,斑点叉尾鮰幼鱼养殖的最适投喂频率为3次/d。