Impact of dietary protein levels and feeding regimes on growth performance and biochemical profile of European sea bass (Dicentrarchus labrax) reared in a brackish water recirculating aquaculture system

The growing importance of European sea bass (Dicentrarchus labrax) in aquaculture underlines the need to optimize the feeding strategy for this fish species. The aim of the present study was to assess the effect of dietary energy content and feeding regime on growth performance, feed utilization and feeding costs for European sea bass. Seven hundreds and four fish ( average initial forthy body weight 68g) were randomly allocated into twelve tanks 800 l in a closed recirculation system (water temperature: 22°C; dissolved oxygen ≥90% of saturation). Three isoproteic (47% crude protein) extruded diets were formulated with different lipid levels i.e. 16% (diet D16), 24% (diet D24) and 32% (diet D32) and each diet was fed at two different feeding regimes (satiation and 80% satiation) according to a bifactorial experimental design. Feed intake (FI) was recorded daily. After 77 days, fish were bulk weighed and growth, SGR and FCR were calculated. Feeding regimes affected all the analysed parameters (P<0.05), whereas diet influenced only FCR, FI, protein and lipid intake and the economic efficiency ratio (EER). Fish fed the lowest energy content diet (D16) to satiation resulted in the highest feed intake, a FCR similar to that of fish fed diets D24 and D32 and in the lowest EER.

This study investigated the effects of dietary protein source and feeding regime (apparent satiation and rationed) on growth performance, nutrient digestibility, fatty acid (FA) profile, and fillet quality traits in rainbow trout. A stock of 1200 juvenile trout (mean weight 114.6 ± 0.2 g) were randomly distributed into 24 fiberglass tanks (four diets × three replications × two feeding regimes). The experimental diets were formulated to be isoproteic and isoenergetic based on bacterial protein meal (BPM), pea protein concentrate (PPC), mixture thereof (MIX), and fish meal (FM), respectively. The feeding trial lasted 77 d with water temperature of 13 C. Statistical differences appeared among the diets only in terms of crude protein digestibility. Growth performance and somatic indexes were significantly affected by the diet, while only the condition factor was influenced by the feeding regime. None of the parameters appeared to be affected by the interaction effects. Differences appeared between the FA profiles of the dorsal muscle. Oleic, linoleic, α‐linolenic, and docosahexaenoic acid contents were influenced by diet, while only minor FAs were influenced by feeding regime. In conclusion, growth performance and nutrient digestibility resulted lower in fish fed BPM diet than other groups, while PPC group was similar to FM group.

Simple SummaryThe effects of increasing temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax) were evaluated through a fish trial lasting 56 days. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those reared at 20 °C. On the other hand, the sea bass condition index did not change among treatments. Additionally, sensory analysis (the Quality Index Method) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness conditions. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile of this particular species in aquaculture.A fish trial was carried out to evaluate the combined effects of temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax). Fish were kept for 56 days at 20 °C and 24 °C and fed on two diets, with 16% and 20% lipid. At the end of the trial, fish were euthanized at two temperature conditions (0.6 °C or −0.6 °C) and kept on ice for 10 days at 4 °C to evaluate their freshness condition. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those at 20 °C. Additionally, sensory analysis (Quality Index Method—QIM) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. However, the 16S rRNA metabarcoding analyses revealed a higher proliferation of genera associated with fish-spoiling bacteria in the skin microbiome of fish reared at 24 °C, i.e., Vibrio and Acinetobacter, which was not observed in the skin microbiome of fish reared at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile (lower QIM and lower CFUs/cm2) of this particular species. Additionally, the lower euthanasia temperature (−0.6 °C) seems to lead to higher fish freshness than the normal temperature (0.6 °C).

Growth, feed conversion and mortality of cagereared tambaqui, Colossoma macropomum, fed various dietary feeding regimes and protein levels

Lee, J. H., Kim, J. D., Kim, J. H., Kim, I. H., Han, In K. 2001. Effect of different dietary CP levels on the growth, nutrient utilization and carcass characteristics of finishing barrows and gilts reared in phase feeding regimen. J. Appl. Anim. Res., 19: 145–163. This experiment was to investigate the effects of different crude protein (CP) sequences on growth performance, nutrients utilization and carcass characteristics of finishing barrows and gilts under three phase feeding regimen. A total of 120 finishing pigs (LandracexLarge WhitexDuroc) averaging 53.3±0.91 kg of body weight and 30 pigs (averaging 52.5±0.57. 81.8±0.79 and 100.7±0.89, respectively) were assigned to the feeding and the metabolic trial, respectively. Experiment was arranged as a 2x3 factorial design, barrows and gilts and three dietary treatments. Each treatment had four replicates with five pigs per replicate. Finishing period (53 to 107 kg) was divided into three phases (53 to 69 kg, 69 to 88 kg and 88 to 107 kg). Dietary treatments included 1) 17%-15%-13% (high CP), 2) 16%-14%-12% (medium CP), 3) 15%-13%-11% (low CP) sequence for finishing period. During the overall experimental period (53 to 107 kg), there was no interaction between sexes and dietary CP levels on growth performances. Barrows consumed more feed (p<0.01) and grew faster (p<0.01) than gilts did. ADG of pigs fed on high dietary CP feeding group was improved significantly than that of pigs fed on low dietary CP feeding group (p<0.05). Average values of essential amino acids (EAA), non-essential amino acids (NEAA) and total amino acids digestibilities were generally not influenced by dietary CP levels and sexes. However, fecal daily nitrogen (N) excretion averaged over all periods was significantly higher in high dietary CP feeing group than in medium and low dietary CP feeding groups (p<0.05). Averaged blood urea nitrogen (BUN) concentration was greater (p<0.05) in barrows than in gilts and was increased as dietary CP concentration increased (p<0.05). Backfat (BF) thickness was greater in barrows than in gilts (p<0.05). Longissimus muscle area (LEA) was greater in gilts than in barrows (p<0.01) and was greater in high and medium dietary CP feeding regimens than in low dietary CP feeding regimen (p<0.05). It is concluded that 16%-14%-12% dietary CP sequence is desirable in respect of economics and environment for practical three phase feeding regimen for gilts and barrows during finishing period.

Polyculture of European seabass and Nile tilapia in the recirculating aquaculture system with brackish water: Effects on the growth performance, feed utilization, and health status

A factorial experiment was conducted to examine effects of dietary protein concentration (24, 28, 32, or 36%) and feeding regimen (feeding once daily or every other day [EOD]) on channel catfish, Ictalurus punctatus, production in earthen ponds. Compared with fish fed daily, fish fed EOD had lower feed consumption, weight gain, net production, and percentage of market‐size fish but had high feed efficiency and required fewer hours of aeration. Fish fed EOD also had lower carcass yield, fillet yield, and visceral and fillet fat. There was a significant interaction between dietary protein and feeding regimen for weight gain. No significant differences were observed in weight gain of fish fed daily with diets containing various levels of protein, whereas weight gain of fish fed EOD with a 24% protein diet was lower than those fed EOD with higher protein diets. Results suggest that response of channel catfish to dietary protein levels depends on whether the fish were fed daily or EOD. Feeding EOD to satiation improved feed efficiency and required less aeration compared with fish fed daily but also reduced net production and processing yield; therefore, EOD feeding should be examined closely before implementation.

The effects of different feeds and feeding regimes on growth performance, flesh quality and fecal viscosity of Atlantic salmon (Salmo salar L.) in recirculating aquaculture systems (RAS) were investigated. Fish (initial body weight of 1677 g +/- 157 g) were fed with four commercial feeds (Nosan salmon-NS, Aller gold-AG, Skretting salmon-SS and Han ye-HY) in two feeding regimes (80% and 100% satiation) for 78 d. The results showed that salmon specific growth ratio (SGR) and weight gain ratio (WGR) were significantly affected by feed type and feeding regime (P < 0.05). Feed conversion ratio (FCR) varied between 0.93 and 3.40, which was significantly affected by feed type (P < 0.05), and slightly improved with increased satiation degree. The activities of digestive enzymes including protease, lipase and amylase were also significantly affected by feed type and feeding regime (P < 0.05), increasing with satiation degree. Flesh qualities for vitamin E, hydroxyproline (HYP), liquid loss and muscle pH among all groups showed significant differences (P < 0.05), ranging from 26.67 to 29.67, while no obvious difference was found in flesh color. Fecal viscosity for different treatments showed no significant difference, though improvement was found in 100% satiation group. From present experiment, it was concluded that both feed type and feeding regime can affect the important quality attributes of Atlantic salmon.

Simple SummaryThere is a growing need to use more efficient feed in fish farming. Designing a proper diet could potentially overcome even negative environmental impacts on the growth of farmed fish. It has been repeatedly stated that the change in temperature followed by the change of seasons can significantly affect the growth of fish. The aim of this work is to study the interaction of the diet (specifically the percentage of fat in it) with the change of temperature in the growth performance, feed utilization and fat deposition of Sea Bass (Dicentrarchus labrax). We used two different temperature regimes (starting at 23 °C and then changed to 17 °C and starting at 17 °C and then changed to 23 °C); fed one of the two commercial diets 16.5 and 20% lipids. We observed better growth rate and feed consumption when fish transferred to warmer water, but no diet-temperature interaction was observed. Different temperature regimes did not affect muscle or liver composition but the different fat diet content affected somatic indexes. In both temperature regimes, for a higher feed intake and body weight, a high fat diet is a better practice.This study was conducted to elucidate the interaction effects of temperature and dietary lipid levels (2 × 2 factorial experiment) on the growth performance, muscle, and liver composition in adult farmed European sea bass (Dicentrarchus labrax). Two groups of fish (190 g; 60 fish per group) were distributed in 12 tanks in triplicates and kept at two different temperature regimes; one starting at 23 °C and then changed to 17 °C for 61 days, and the other starting at 17 °C and then changed to 23 °C for 39 days. Two commercial diets containing both ~44% crude protein but incorporating different dietary lipid levels, 16.5% (D16) and 20.0% (D20) (dry matter (DM)), were fed to the fish to apparent satiation; the type of diet fed to each fish group remained constant throughout the experiment. Final body weight, weight gain, and specific growth rate were significantly higher for the fish group held at 23 °C compared to the fish group at 17 °C (before the temperature changes), while the dietary fat content did not have any profound effect in both groups. Furthermore, the different temperature regimes did not affect muscle or liver composition, but, on the contrary, dietary lipids affected hepatosomatic, perivisceral fat, and visceral indexes. Feed conversion ratio and specific growth rate were not affected by the dietary lipid level. An interaction of temperature and dietary lipid content was observed in daily feed consumption (DFC) and final body weight (FBW).

A 90-day feeding trial was conducted to study the effect of qualitative and quantitative restricted feeding strategies on nutrient utilization and growth performance of rohu, Labeo rohita. Two experimental iso-caloric (355.82 - 357.58 kcal/100g) diets with two crude protein levels of 30% and 25% designated as diet A and B, respectively were prepared. One hundred and eighty fingerlings (3.95±0.06g)were distributed into five treatments in triplicates. The experimental design consists 1. Continuous feeding of diet A (T30, C); 2. Continuous feeding of diet B (T25); 3. Alternate feeding of diet A and diet B (T30/25); 4. Alternate day satiation feeding and starvation of Diet A (T30-1);and 5. Alternate day satiation feeding and starvation of Diet B (T25-1). Feeding was done twice daily throughout the experimental period. Results revealed that the dietary feeding regimes significantly affected growth parameters (P&lt;0.05). However, growth performance in terms of specific growth rate (% SGR) and weight gain percent were similar among T30 (C), T30/25 andT30-1 groups. The FCR and PER of fish in dietary regimes T30-1 and T25-1 were better than feeding regime group of T30/25. Overall results of present study indicated that continuous feeding of 30% crude protein exhibited similar growth with that of 30% crude protein feeding followed by starvation(T30-1). From the economic point of view, feeding 30% of protein followed by one day starvation can be an alternative feeding strategy for grow-out culture of rohu.

Influence of feeding diets with and without fish meal by hand and by self-feeders on feed intake, growth and nutrient utilization of juvenile rainbow trout ( Oncorhynchus mykiss)

The aim of this study was to evaluate the effects of increasing dietary arachidonic acid (ARA) levels (from 1 to 6% of total fatty acids) on European sea bass (Dicentrarchus labrax) juveniles' growth performance, tissue fatty acid profile, liver morphology as well as long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis, triglyceride and cholesterol synthesis and lipid transport. A diet with total fish oil (FO) replacement and defatted fish meal (FM) containing a 0.1-gARAg-1 diet was added to the experimental design as a negative control diet. Dietary ARA inclusion levels below 0.2gARAg-1 diet significantly worsened growth even only 30days after the start of the feeding trial, whereas dietary ARA had no effect on fish survival. Liver, muscle and whole body fatty acid profile mainly reflected dietary contents and ARA content increased accordingly with ARA dietary levels. Tissue eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) levels were positively correlated among them. Hepatic lipid vacuolization increased with reduced dietary ARA levels. Expressions of fatty acyl desaturase 2 and 3-hydroxy-3-methylglutaryl-coenzyme genes were upregulated in fish fed the negative control diet compared to the rest of the dietary treatments denoting the influence of ARA on lipid metabolism. Results obtained highlight the need to include adequate n-6 levels and not only n-3 LC-PUFA levels in European sea bass diets.

Effects of feeding low fishmeal diets with increasing soybean meal levels on growth, gut histology and plasma biochemistry of sea bass

Two studies were conducted to evaluate the effects of (I) high-protein (38%) finisher feed fed to satiation for 30,45,60, or 90 days prior to harvest and (2) dietary protein (32 vs. 38%) and feeding regimen (satiation or restricted) on growth and fattiness of channel catfish. Each study was conducted for two years in earthen ponds stocked with channel catfish at a rate of 13,590 fish/ha (35 to 40 g initial weight) for year 1 and 6,800 fish/ha (0.45 to 0.6 kg initial weight) for year 2. Years refer to year of experiment and not fish age class. There were no significant differences in total yield, dressed yield, or muscle fat, regardless of diet or feeding regimen within year. Year-one fish (study 2) fed to satiation tended to gain more weight and appeared to convert feed better than fish fed at a restricted rate. In study 2 there were significant interactions between year and feed, and between year and feeding regimen. Percentage visceral fat was reduced by feeding a high-protein feed during year 1 (study ...

A sustainable growth of the aquaculture sector implies the use of sustainable novel raw materials as replacers of the traditional fishmeal (FM) and fish oil (FO) ingredients. This fact has led to the development of sustainable and functional diets as part of a management strategy to reduce the effects on fish growth performance and health derived from low FM/FO dietary contents. In this sense, Antarctic krill (Euphausia superba) is considered a potential candidate in dietary inclusions to potentiate fish growth and health status. In this study, European sea bass (Dicentrarchus labrax) were fed a practical diet with either a 15% fishmeal content (KM0; control diet) or the same diet substituted by 30% (KM5; 50 g KM/kg diet) or 50% (KM7.5; 75 g KM/kg diet) Antarctic krill meal (KM) for 12 weeks in triplicates. At the end of the feeding trial, growth performance, liver morphology, liver proximate composition, lipid classes and fatty acid profiles, as well as the expression of hepatic genes related with lipid metabolism were evaluated. Fish fed KM-based diets presented higher (p < 0.05) final weight, protein and lipid efficiency ratios, specific growth rate (SGR) and improved feed conversion ratio (FCR), irrespective of the KM dietary level. Whole body and muscle proximate composition and fatty acid profiles were similar among dietary groups. Livers of European sea bass fed the experimental diets presented similar (p > 0.05) biochemical composition and fatty acid profile. However, smaller hepatocellular area and lower grade of cytoplasm vacuolization as well as a better alignment around sinusoidal spaces were found. The analyses of liver lipid classes revealed a positive correlation between the level of dietary KM and the pigmented material such as astaxanthin and free fatty acid content, as well as a negative correlation with the cholesterol levels. The expression of hepatic genes studied demonstrated a downregulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr) and delta-6-desaturase (fads2) expression levels in fish fed KM-based diets. Besides, gene expression levels of fatty acid binding protein 7 (fabp7) and lipoprotein lipase (lpl) were significantly correlated with KM dietary levels. Altogether, these results profile KM as a potential promoter of growth and liver health in European sea bass fed low fish meal and oil diets.