Feed Efficiency Of Fish Research Articles

Isogenic lines of rainbow trout (Oncorhynchus mykiss) as a tool to assess how growth and feeding behaviour are correlated to feed efficiency in fish

Accurately measuring individual feed intake is required to include feed efficiency (FE) as an objective in commercial breeding programs. Phenotyping individual feed intake through direct measurements remains complex in fish reared in groups. One way to overcome this challenge is to find proxies for estimating FE. This study aimed to investigate the correlations between fish FE and potential predictive criteria in rainbow trout Oncorhynchus mykiss. As predictive criteria, we considered the variations of body weight assessed as thermal growth coefficients (TGC) and the feeding behaviour assessed as the number of feed demands over a period and the proportion of the demands made before noon. Feed intake was assessed over three different periods in ten isogenic lines allowing a recording for each of the ten genotypes while keeping fish in groups. The protocol consisted of two successive feed deprivation and refeeding phases after initial basal growth periods. Correlations were then calculated between FE, measured either as feed conversion ratio (FCR) or residual feed intake (RFI), and the different indirect criteria. We found positive phenotypic correlations between FCR and RFI over the feed intake measurement periods (r ⩾ 0.79, P < 0.001). Assessment of the relationship between FE traits (FCR and RFI) calculated over the three measurement periods and TGC revealed no significant association. Regarding feeding behaviour, significant differences in the daily profile of feed demands and their numbers were found among the ten isogenic lines. RFI calculated from the first feed intake measurement period and feeding behaviour, assessed as the number of feed demands were positively correlated (r = 0.42–0.49, P ⩽ 0.022). Nevertheless, such correlations were not established for the two other measurement periods following feed deprivation. While we demonstrated that the weight variations during feed deprivation are not a good proxy for FE (FCR or RFI) in rainbow trout, we also highlighted the interest in exploring more the relationships between FE and feeding behaviour in fish.

Isotope fractionation in juvenile and large rainbow trout (Oncorhynchus mykiss): Repeatability of stable isotope measures and their relationship to growth rate

The study aimed to assess the repeatability of isotope ratios, δ13C and δ15N in four tissues (muscle, liver, adipose fin, and visceral adipose) and the relationship between growth rate and these measures in rainbow trout (Oncorhynchus mykiss). Tissue samples were from two experiments with, respectively, juvenile (n = 10; Experiment 1, one tank) and large (n = 120; Experiment 2, three tanks) rainbow trout, fed commercial diets. In Experiment 2, the estimated repeatability was high for both δ13C and δ15N in muscle and liver, making one measure suffice (r = 0.70–0.78 and r = 0.80–0.91, respectively). Using regression analysis, bioaccumulation of δ13C in muscle and δ15N in liver (over life), through fractionation (without feed enrichment or depletion strategies) was found to be, respectively, negatively and positively associated with growth rate. Even though individual feed intake was not recorded, the significant relationship between GR (that correlates with feed efficiency) and, respectively, MC and LN, suggests isotopic fractionation as potential biomarkers for individual cumulative (over-life) feed efficiency in fish.

Effects of dietary protein and lipid levels on growth, feed utilization and meat quality of clown knifefish (Chitala chitala)

Effects of dietary protein and lipid levels on growth, feed utilization and fillet quality of clown knifefish (Chitala chitala) were implemented to determine the protein and energy requirements of this species at 400 g stage. A 4 x 3 factorial design with four dietary protein levels (25%, 30%, 35% and 40%) and three dietary lipid levels (6, 9, and 12%) corresponded to 3 energies levels 18, 19 and 20 MJ/kg. Clown knifefish (407 ± 5.0 g) was stocked at a density of 10 fish/m2. The experiment was arranged in a completely randomized design in triplicate tanks for 8 weeks. There was a significant interaction effect (P&lt;0.05) between protein and lipid levels on weight gain and specific growth rate with the fish growth being highest in the 35 CP-9% lipid treatment. The survival rate of fish was not affected (P&gt;0.05) by dietary protein and lipid levels and ranged from 93.3 to 100%. The feed efficiency of fish was influenced by dietary protein or lipid content as well as the interaction between these two factors. Protein utilization efficiency increased as protein content increased, and diet contained t 35% protein and 9% lipid, enhanced chewiness and hardness of fish paste. These results showed that clown knifefish fed 32.8% dietary protein and 19 MJ energy with a P/E ratio of 18.6 had the optimal growth and the best quality of fish meat.

Determination of Digestive Enzyme Activity in Gilt-Head sea bream (Sparus aurata ) Feeding with Commercial Feed

With the increase in the world population, aquaculture has a very important place in meeting the protein needs of humanity. Today, fish farming is developing rapidly depending on the increase in demand. Fish is one of the most important foodstuffs for human nutrition. Studies on the quality and characteristics of the feeds used gain importance with the increase in the knowledge about the nutrient sources of fish. It is known that there is a linear correlation between growth, productivity and feed efficiency in fish like another animal. At this point, the correct and effective use of feed, which is the most important input in production, is very important in terms of increasing the yield and product quality to be obtained from the product and reducing production costs. The identification of digestive enzyme activities is important in developing new feeding regimens and in ensuring optimal growing conditions. As most enzymes regulate the events of viability, the increase or decrease in their activity causes the degradation of the normal functions of fish and diseases in fishes. In this study, body weight and changes in digestive enzyme activity were investigated in sea bream feeding with commercial feed. For this purpose, a total of 3000 juveniles with an initial mean weight (IW) of 2.72±0.78 g were divided into 4 tanks (2000 L). After the six weeks final weight was 7.75 ± 0.67 at the end of experiment. While trypsin activity was increased until the end of the experiment, amylase activity was decreased. On the other hand, small decreases in lipase activity were observed throughout the experiment.

Hepatic Glucose Metabolism and Its Disorders in Fish.

Carbohydrate, which is the most abundant nutrient in plant-sourced feedstuffs, is an economically indispensable component in commercial compound feeds for fish. This nutrient can enhance the physical quality of diets and allow for pellet expansion during extrusion. There is compelling evidence that an excess dietary intake of starch causes hepatic disorders, thereby further reducing the overall food consumption and growth performance of fish species. Among the severe metabolic disturbances are glycogenic hepatopathy (hepatomegaly caused by the excessive accumulation of glycogenin hepatocytes) and hepaticsteatosis (the accumulation of large vacuoles of triacylglycerols in hepatocytes). The development of those disorders is mainly due to the limited ability of fish to oxidize glucose and control blood glucose concentration. The prolonged elevations of blood glucose increase glucose intake by the liver, and excess glucose is stored either as glycogen through glycogenesis in hepatocytes or as triglycerides via lipogenesis in tissues, depending on the species. In some fish species(e.g., largemouth bass), the liver has a low ability to regulate glycolysis, gluconeogenesis, and glycogen breakdown in response to high starch intake. For most species of fish, the liver size increases with lipid or glycogen accumulation when they have a high starch intake. It is a challenge to develop the same set of diagnostic criteria for all fish species as their physiology or metabolic patterns differ. Although glycogenic hepatopathy appears to be a common disease in carnivorous fish, it has been under-recognized in many studies. As a result, understanding these diseases and their pathogeneses in different fish species is crucial for manufacturing cost-effective pellet diets to promote the health, growth,survival, and feed efficiency of fish in future.

Impacts of dietary konjac glucomannan supplementation on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in golden pompano (Trachinotus ovatus) fed a high fat diet

This study examined the effect of konjac glucomannan (KGM) supplementation in diets with different lipid levels on growth, antioxidant capacity, hepatic lipid metabolism and inflammatory response in juvenile pompano (Trachinotus ovatus). Triplicate groups of fish (12.07 ± 0.21 g) were fed eight experimental diets containing two lipid levels of 9% (basal-fat diet, BFD) and 18% (high-fat diet, HFD), and four levels of KGM (0, 0.5, 1 and 2%) for 60 days. Pompano fed HFD exhibited markedly lower growth and feed efficiency than fish fed BFD, and KGM supplementation, particularly at 1% inclusion, significantly improved growth performance and feed efficiency in fish fed both BFD and HFD. In addition, Pompano fed HFD showed higher whole-body lipid and lower protein contents than fish fed BFD. Irrespective of dietary lipid level, whole body, dorsal and ventral muscle were reduced by dietary KGM supplementation up to 1% while the opposite was found for whole body protein content. Dietary KGM also significantly reduced the HSI, liver lipid contents, as well as lipid droplets in the liver. Supplementation of KGM to both BFD and HFD significantly reduced serum total cholesterol, triglyceride, low-density lipoprotein cholesterol and free fatty acids levels. Furthermore, irrespective of dietary lipid level, increasing dietary KGM supplementation enhanced serum IgM level, lysozyme and alkaline phosphatase activities, and reduced serum alanine aminotransferase and aspartate aminotransferase activities. Dietary KGM also increased liver total antioxidant capacity, superoxide dismutase and catalase activities, and decreased malondialdehyde concentration in fish fed both HFD and BFD. Dietary KGM significantly increased serum glutathione peroxidase, superoxide dismutase and catalase activities and reduced malondialdehyde concentrations in fish fed BFD, and enhanced serum total antioxidant capacity and glutathione peroxidase activity in fish fed HFD. Supplementation of KGM increased the expression of genes associated with lipid catabolism (pparα, cpt1, hsl) and lipid transport (fabp1, apoB100 and cd36), and decreased the expression of lipid anabolism related genes (srebp1, pparγ, fas and acc). Moreover, the expression of pro-inflammatory cytokines including tumor necrosis factor α and interleukin-8 were down-regulated, while expression of the anti-inflammatory cytokine transforming growth factor β1 was increased by KGM supplementation. In conclusion, supplementation of KGM at 1% of diet improved growth, feed efficiency, antioxidant capacity, hepatic lipid metabolism and inflammatory responses in juvenile pompano, and can mitigate excessive deposition of lipid in tissues of farmed fish.

Evaluation of the optimum dietary essential amino acid pattern for adult pacu (Piaractus mesopotamicus)

The optimum levels of essential amino acids (EAAs) are required to be maintained in fish feed for obtaining normal body protein synthesis and muscle growth. This study aimed to determine the optimum dietary EAA pattern for adult pacu (Piaractus mesopotamicus) by the amino acid (AA) deletion method. A total of 165 adult fish of 1109.83 ± 14.26 g (initial body weight ± standard deviation) were equally distributed among 11 treatments in a recirculation aquaculture system. Each of the 11 treatments consisted of three randomly arranged replicates (tanks) and 5 fish were stocked per tank. During the 60-day experimental period, fish were fed with 11 diets including a control diet (CD) and 10 EAA limiting diets (LDs) two times daily until apparent satiation. The body nitrogen (N) retention and weight gain in fish fed with EAA LDs was lower (P < 0.05) than the CD. The feed efficiency in fish fed with CD was similar (P > 0.05) to most EAA LDs, except arginine and histidine LDs. The specific growth rate in fish fed with tryptophan, arginine and histidine LDs was different (P < 0.05) as compared to the CD. Based on the present N retention data obtained through the AA deletion method, the optimum pattern of dietary EAAs estimated in relation to lysine requirement (100%) was as follows: arginine 72.16%; phenylalanine 40.83%; histidine 30.15%; isoleucine 53.01%; leucine 81.71%; methionine 24.97%; threonine 58.20%; tryptophan 9.13% and valine 54.69%.

Use of Corn Husk Meal in the Development of a Functional Diet for Nile tilapia (Oreochromis niloticus) Fingerlings: Effect on Growth Performance, Antioxidant Status and Intestinal Microbiota

The effect of dietary supplementation of corn husk meal (CHM) on growth performance, liver antioxidant status and intestinal microbiota in Nile tilapia (Oreochromis niloticus) fingerlings was evaluated. Four experimental groups of fish with initial weight 0.47 ± 0.7 g in triplicate tanks were used; three of them were fed CHM incorporated diets (12.5 g/kg, DH12; 25 g/kg, DH25; and 50 g/kg, DH50), whereas a CHM-free basal diet served as control (DH0). No significant differences were observed in growth performance or feed efficiency in fish fed experimental diets (P > 0.05); however, fish fed the DH50 diet had a significant higher proportion of crude protein of whole-body composition (P < 0.05). Analysis of antioxidant enzyme activity showed significant differences (P < 0.05) with higher superoxide dismutase (SOD) activity in fish fed the DH25 diet, and lower glutathione peroxidase (GPx) activity in fish fed the DH12 diet. No significant differences were found in catalase (CAT) activity between treatments. Fusobacteria, Bacteroidetes and Proteobacteria were the most abundant phyla in all feces samples but no significant differences were found in microbial diversity among diets. Results suggest that CHM is safe for Nile tilapia consumption improving crude protein of whole-body composition and enhancing SOD activity.

Enhanced biodiversity of gut flora and feed efficiency in pond cultured tilapia under reduced frequency feeding strategies.

Feed constitutes 50-70% of total production costs of tilapia, one of the most widely cultured finfishes in the world. We evaluated reduced-feeding strategies for improving production efficiency of Nile tilapia (Oreochromis niloticus). In a 12-week pond trial, fish were fed daily, every other day, every third day, or not at all. Ponds were fertilized to enhance natural foods. In a fifth group fish were fed daily without pond fertilization. Fish fed daily with or without pond fertilization and fish fed every other day had higher specific growth rates, survivability, and net production than the other two treatments. Fish feed efficiency and benefit to cost ratio was highest for treatments fed in a pulsatile manner (i.e. fed every other day or every third day) with fish fed on alternate days providing the best net return among all groups. Fish fed on alternate days had more moderate gene expression levels of intestinal nutrient transporters which may allow for a more balanced and efficient nutrient uptake. Fecal microbe analyses identified 145 families of prokaryotic and 132 genera of eukaryotic organisms in tilapia. The highest diversity of prokaryotes was found in fish fed either every other day or daily in fertilized ponds and the highest diversity of eukaryotes was found in fish fed every other day. These studies indicate feeding Nile tilapia on alternate days along with weekly pond fertilization has no deleterious effects on growth, survivability, or production versus daily feeding regimes, but enhances feed efficiency by 76% and provides the greatest net return on investments. Our studies also suggest for the first time that combining alternate-day feeding with pond fertilization produces the greatest microbial biodiversity in the intestine that could contribute to enhanced feed efficiency and overall health of tilapia.

Application of organic fertilizer on swamps pond for catfish (Pangasius sp.) culture

Swamp fish pond has a problems related to submerged flat soil and water pH value and result in low productivity of ponds. Fertilization increase productivity of pond water by providing nutrients for fish food organisms, The objective of this research was to determine the best dosage of organic fertilizer to improve water quality and pond productivity and it’s effect to survival and absolute growth of catfish Pangasius sp. The research was conducted with using completely randomized design with four treatments and three replications. All of ponds unit were limed using dolomite of 10 ton/ha, incubated for 13 days, then gave four difference dosage of organic fertilizer, that were without fertilizer (P0), with fertilizer of 100 g/m2 (P1), 170 g/m2 (P2), and 240 g/m2 (P3). Pangasius sp. fish (average body length of 5±0.5 cm) was stocked with the density of 15 fish/m2 and cultured for 30 days. The parameters observed were soil (pH, N, P2O5, Ca, and C-organic) and water quality (pH, alkalinity, temperature, dissolved oxygen, ammonia, total Phosphate, Ca, and TOC), pond productivity, density of phytoplankton, survival, absolute growth, feed efficiency, and production of fish. The data were statistically analyzed by one-way ANOVA, Least Significant Difference test, and regression models analysis. The results showed that P1 (100 g/m2 of fertilizer) was the best dosage indicated by pH 7.60, nitrogen 0.13%, P2O5 0.16%, Ca 2.59%, C-organic 1.49% of pond soil; pH 7.42, temperature 27.3-32.4°C, dissolved oxygen 4.94-5.09 mgL−1, alkalinity 51.33 mgL−1, Ca 55 mgL−1,TOC 12.3 mgL−1, ammonia 0.24 mgL−1, Total Nitrogen (TN) 3.78 mgL−1, Total Phosphate (TP) 0.109 mgL−1 of pond water. Based on TN:TP (10.09) of water showed nutrient was balanced. Productivity of ponds was on eutrophic state based on both TN and TP. Survival rate of catfish was 100%, absolute gain of weight 8.46 g and lenght 3.99 cm, Feed efficiency of fish was 101.55% and the density of phytoplankton was 217 cell/mL.

Growth and body composition of juvenile curimata pacu (Prochilodus argenteus) fed diets with different protein: lipid ratios

Promising species for aquaculture need to have their nutritional requirements defined. Considering that protein is the most expensive macronutrient in aquaculture diets, the present study aimed to estimate the protein requirement of curimata-pacu fed with diets containing two lipid levels. Thus, eight experimental diets were formulated to contain 20, 25, 30 and 35% of crude protein (CP) associated to 11 and 15% of crude lipids (CL) were formulated, constituting a completely randomized factorial design (4 CP x 2 CL) with three replicates per treatment. The juveniles (3.6 ± 0.01 g) were fed daily with 6% of the biomass, three times a day (08:00, 12:00 and 16:00 h) for 70 days. The protein requirement was estimated by the combination of the broken line and quadratic regression models. The CP concentration in the diets was the only factor influencing ( P 0.05) with the CL level of the diets. The requirement for weight gain and fish feed efficiency was estimated at 32.5 and 34.5% CP. Protein retention decreased ( P < 0.05) in proportion to CP elevation. Fish fed 15% CL had higher ( P < 0.05) body lipid deposition. On the other hand, the increase of CP of the diets decreased ( P < 0.05) lipid deposition in juveniles. Therefore, it is recommended that young curimata-pacu between 3 and 27 g in weight should be fed diets containing 32.5-34.5% CP and 11% of CL, equivalent to a protein: energy ratio of 22-23 mg kJ -1 .

Quantifying the genetic parameters of feed efficiency in juvenile Nile tilapia Oreochromis niloticus

BackgroundImproving feed efficiency in fish is crucial at the economic, social and environmental levels with respect to developing a more sustainable aquaculture. The important contribution of genetic improvement to achieve this goal has been hampered by the lack of accurate basic information on the genetic parameters of feed efficiency in fish. We used video assessment of feed intake on individual fish reared in groups to estimate the genetic parameters of six growth traits, feed intake, feed conversion ratio (FCR) and residual feed intake in 40 pedigreed families of the GIFT strain of Nile tilapia, Oreochromis niloticus. Feed intake and growth were measured on juvenile fish (22.4 g mean body weight) during 13 consecutive meals, representing 7 days of measurements. We used these data to estimate the FCR response to different selection criteria to assess the potential of genetics as a means of increasing FCR in tilapia.ResultsOur results demonstrate genetic control for FCR in tilapia, with a heritability estimate of 0.32 ± 0.11. Response to selection estimates showed FCR could be efficiently improved by selective breeding. Due to low genetic correlations, selection for growth traits would not improve FCR. However, weight loss at fasting has a high genetic correlation with FCR (0.80 ± 0.25) and a moderate heritability (0.23), and could be an easy to measure and efficient criterion to improve FCR by selective breeding in tilapia.ConclusionAt this age, FCR is genetically determined in Nile tilapia. A selective breeding program could be possible and could help enabling the development of a more sustainable aquaculture production.

Phenotyping for Genetic Improvement of Feed Efficiency in Fish: Lessons From Pig Breeding.

Feed incurs most of the cost of aquaculture production, so feed efficiency (FE) improvement is of great importance. Our aim is to use work done in pigs to formulate a logical framework for assessing the most useful component traits influencing feed intake (FI) and efficiency in farmed fish – either to identify traits that can together be used for genetic improvement of FE, or as substitute traits for FI recording. Improvement of gross FE in growing fish can be accomplished by selection for increased growth rate. However, the correlation of growth with FE is typically only modest, and hence there is room for further improvement of FE through methods other than growth selection. Based on a literature review we propose that the most effective additional methods are selection for reduced body lipid content and for reduced residual FI (RFI). Both methods require more or less sophisticated recording equipment; in particular, the estimation of RFI requires recording of FI which is a challenge. In mammals and birds, both these approaches have been effective, and despite the high costs of FI recording, the RFI approach can be cost-efficient because maintenance requirements are high and therefore RFI variation covers a large part of FI variance. Maintenance requirements of fish are lower and therefore RFI variation covers a smaller part of FI variance. Moreover, accurate high-volume routine individual FI recording is much more challenging in fish than in mammals or birds. It follows that selection for reduced body fat content is likely a more effective (and certainly more cost-efficient) way to improve feed conversion ratio in fish than selection for reduced RFI. As long as body fat content is dealt with as an explicit selection criterion, the only valid reason for FI recording would be the requirement of RFI reduction. So, if RFI reduction is not required, there would be no need for the expense and effort of individual FI recording – and in fish breeding that would be a very desirable situation. Solid evidence for these propositions is still scarce, and their generality still needs to be confirmed.

Near infrared computer vision and neuro-fuzzy model-based feeding decision system for fish in aquaculture

In aquaculture, the feeding efficiency of fish is of great significance for improving production and reducing costs. In recent years, automatic adjustments of the feeding amount based on the needs of the fish have become a developing trend. The purpose of this study was to achieve automatic feeding decision making based on the appetite of fish. In this study, a feeding control method based on near infrared computer vision and neuro-fuzzy model was proposed. The specific objectives of this study were as follows: (1) to develop an algorithm to extract an index that can describe and quantify the feeding behavior of fish in near infrared images, (2) to design an algorithm to realize feeding decision (continue or stop) during the feeding process, and (3) to evaluate the performance of the method. The specific implementation process of this study was as follows: (1) the quantitative index of feeding behavior (flocking level and snatching strength) was extracted by Delaunay Triangulation and image texture; (2) the adaptive network-based fuzzy inference system (ANFIS) was established based on fuzzy control rules and used to achieve automatically on-demand feeding; and (3) the performance of the method was evaluated by the specific growth rate, weight gain rate, feed conversion rate and water quality parameters. The results indicated that the feeding decision accuracy of the ANFIS model was 98%. In addition, compared with the feeding table, although this method did not present significant differences in promoting fish growth, the feed conversion rate (FCR) can be reduced by 10.77% and water pollution can also be reduced. This system provides an important contribution to realizing the real-time control of fish feeding processes and feeding decision on demand, and it lays a theoretical foundation for developing fine feeding equipment and guiding practice.

Improving feed efficiency in fish using selective breeding: a review

AbstractImproving feed efficiency (FE) is key to reducing production costs in aquaculture and to achieving sustainability for the aquaculture industry. Feed costs account for 30–70% of total production costs in aquaculture; much work has been done on nutritional and husbandry approaches to improve FE but only a limited amount of research has been devoted to using genetics, despite its potential. This paper reviews past work to improve FE in fish using selective breeding and assess future directions. Direct selection on FE traits requires methods to measure individual feed consumption and estimate FE efficiently and accurately. This is particularly difficult to do in fish because of the environment in which they live. Many of the published studies on FE were found to be inaccurate because of methodological problems. The relatively low heritability estimates of FE traits in fish published to date are probably partly as a result of inaccurate measurements of feed intake. Improving ways to measure the individual feed intake with high accuracy will be critical to the successful application of genetics to improving FE. Indirect selection criteria that could be used to improve FE (including growth after starvation/refeeding, body composition, neuropeptides or hormone levels) are discussed. Promising approaches to measuring feed intake accurately that may enable these studies to be undertaken are identified. More work using these will be needed prior to assessing the practicality of the introduction of direct or indirect traits for FE in fish genetic improvement programmes.

Substituição do milho pelo farelo de algaroba (Prosopis juliflora) em dietas para juvenis de tilápia do Nilo cultivados em baixa temperatura

The objective of this study was evaluating mesquite meal as a substitute for corn in diets for Nile tilapia juveniles. Four isoproteic (34% crude protein) and isocaloric (3,150 kcal kg-1 digestible energy) diets were formulated corresponding to replacement levels (0, 33, 66 and 100%) of corn by mesquite meal. Two hundred and forty tilapia juveniles (1.55 ± 0.02 g) were housed in circular tanks (20 fish per tank of 310 L) in a completely randomized experimental design (n = 3). Fish were fed to apparent satiation three meal per day (8:30 a.m., 12:30 p.m. and 4:30 p.m.) for 70 days. Because low water temperature (23.8 ± 1.2 °C), was registered low growth and feed efficiency of fish at experiment. Tilapia juveniles weight gain, feed intake, specific growth rate and body composition were similar (P > 0.05) in all treatments. Survival increased linearly (P < 0.05) with increasing whole mesquite meal levels in diets. Mesquite meal can completely replace corn in Nile tilapia juvenile diets during periods of low water temperature.

Effects of dietary yeast nucleotides on growth, non-specific immunity, intestine growth and intestinal microbiota of juvenile hybrid tilapia Oreochromis niloticus ♀ × Oreochromis aureus ♂.

This study investigated the effect of dietary supplementation of yeast nucleotides on the growth, non-specific immunity, intestine growth and intestinal microbiota of juvenile hybrid tilapia. Tilapia (initial average weight of 8.02 g) was fed test diets supplemented with a yeast-originated nucleotide mixture (0, 0.15, 0.30, 0.60, and 1.20 g/100 g diet) for 8 weeks. Fish fed the diet with 0.60% nucleotide had significantly higher weight gain than the control group (P < 0.05). Feed efficiency was improved in the fish fed 0.60 and 1.20% nucleotide compared with that in the control group. The optimal doses of nucleotides supplementation for growth and feed efficiency of fish were determined as 0.63 and 0.81%, respectively. Intestinal growth was improved in the 0.30 and 0.60% groups, as indicated by significant increase in intestine length. The fish fed 0.60 and 1.20% nucleotide showed higher super oxide dismutase (SOD) activity and lower malondialdehyde (MDA) level in the liver than the control fish, indicating enhancement of the anti-oxidant status. Serum lysozyme activity was significantly increased in the 0.15 and 0.3% nucleotide supplementation groups, suggesting an enhancement effect on the non-specific immune response. Lastly, dietary nucleotides supplementation exerted moderate influence on the intestinal microbiota of hybrid tilapia. A reduction in the cumulative abundance of putative butyrate-producing species was observed in the intestinal microbiota of fish fed diets with 0.60% nucleotide compared with the control, implying an interaction between dietary nucleotides and butyrate production. Briefly, dietary supplementation with 0.60% nucleotide improve the growth performance, immune activity and intestine growth in tilapia.

EVALUATION OF CHITINOLYTIC GUT MICROBIOTA IN SOME CARPS AND OPTIMIZATION OF CULTURE CONDITIONS FOR CHITINASE PRODUCTION BY THE SELECTED BACTERIA

Present study was aimed at isolation of autochthonous chitinase-producing bacteria from the gastrointestinal tracts of 3 Indian Major Carps (Labeo rohita, Catla catla, Cirrhinus mrigala) and 3 exotic carps (Hypophthalmichthys molitrix, Ctenopharyngodon idella, Cyprinus carpio). Altogether, 119 bacteria were isolated from both the proximal and distal intestine and screened for chitinolytic activity. On the basis of chitin hydrolysis zone, 63 isolates were primarily selected for chitinase production, from which 34 potent strains were further studied for quantitative enzyme assay. Amongst them, the strains HMH1 and CMF2 exhibited potent chitinolytic activity and were identified as Bacillus pumilus (KF454036) and Bacillus flexus (KF454035), respectively by 16S rRNA partial gene sequence analysis. Optimization of various fermentation parameters (e.g., temperature, pH, inoculums size, surfactant, colloidal chitin concentration, incubation time, carbon sources, organic and inorganic nitrogen sources) were carried out in chitinase production medium. Incubation for 72 h at 350C and initial pH 7.5 revealed optimum chitinase productions by B. pumilus HMH1 in the media supplemented with colloidal chitin 0.1% (w/v), maltose 2% (w/v), ammonium sulphate 1.0% (w/v) and Tween-80 0.2% (v/v). However, B. flexus CMF2 required 48 h incubation at 35°C and initial pH 8.0 with colloidal chitin 0.15% (w/v), sucrose 1% (w/v), yeast extract 2.0% (w/v) and Tween-20 0.2% (v/v) supplementation for optimum yield. The results indicate that there is ample scope for further research to appraise fish gut microorganisms for chitinase production or as probiotics to improve feed efficiency in fish.

Effect of Dietary Protein and Lipid Levels on Growth and Body Composition of Spotted Halibut, Verasper variegatus

A 83-d feeding experiment was undertaken to evaluate the effects of dietary protein and lipid levels on growth and body composition of spotted halibut, Verasper variegatus (initial average weight of 93.0 ± 1.0 g). Nine diets were formulated to contain three protein levels (40, 45, and 50%), each with three lipid levels (8, 12% and 16%). Each diet was randomly fed to triplicate groups of 20 fish per tank in the indoor culture system. Results showed that the survival rate of fish was not significantly affected by protein and lipid levels (P > 0.05). Weight gain, specific growth rate (SGR), and feed intake (FI) significantly decreased with the increasing dietary lipid levels (P < 0.05). Feed efficiency significantly increased while the feed conversion ration significantly decreased with increasing dietary protein levels (P < 0.05). Weight gain, SGR, FI, and feed efficiency of fish fed 50% protein and 8% lipid were significantly higher than that of the other groups. For each level of dietary lipid, the increase in dietary protein resulted in significant increases in whole-body crude protein (CP) contents (P < 0.05); the increase in dietary lipid caused significant increases in whole-body crude lipid content and gross energy at each protein level (P < 0.05). The muscle CP, lipid, and gross energy had the same tendency. The results of this study indicated that increasing dietary lipid levels did not result in a protein-sparing effect. It could be recommended that the proper dietary protein and lipid levels of spotted halibut were 50 and 8%, respectively.

배합사료 내 Spirulina 함량에 따른 비단잉어 홍백 치어의 체색 변화

Abstract This study was conducted to investigate the effects of Spirulina level in the diet on growth and skin color of red- and white-colored fancy carp Cyprinus carpio var. koi at different feeding periods. Five experimental diets (designated as Con, S5, S9, S13 and S17) were prepared to contain 0, 5, 9, 13 and 17% Spirulina. Each experimental diet was fed to two replicate groups of fish (6.6 g/fish) to visual satiation three times a day for 12 weeks. Weight gain and feed efficiency of fish were not affected by dietary Spirulina level. The values of redness (a*), lightness (L*) and yellowness (b*) of the fish skin were influenced by dietary Spirulina level at different feeding period. The L* value of skin in the fish fed S9, S13 and S17 diets tended to decrease with feeding period. The skin a* value of the fish increased significantly with feeding period and dietary Spirulina level. The skin a* value of the fish fed the diets containing 5-17% Spirulina was higher than that of fish fed control diet at 6 and 12 weeks of feeding. The skin a* value and total carotenoids of the fish fed the S17 diet was the highest among groups. Based on the results of this study, it can be concluded that dietary inclusion of Spirulina powder could increase the skin redness of red- and white-colored fancy carp.Key words: Red- and white-colored fancy carp, Skin coloration, Dietary Spirulina levelCorresponding author : 033-640-2414, smlee@gwnu.ac.kr ( 110076-3) .