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Fishmeal substitution with sustainable feed sources is highly essential towards sustainable production. This study aimed to investigate the effects of substituting fishmeal (FM) with Daphnia magna biomass meal (DBM) or zooplankton biomass meal (ZBM) on growth performance, liver and intestinal histology, gut bacterial abundance and stress tolerance of Nile tilapia, Oreochromis niloticus, fry. Nile tilapia fry (0.23 ± 0.04 g) were randomly assigned to five groups of three replicates. The control diet comprised 300 g/kg FM, and the FM was substituted with DBM or ZBM at levels of 25% and 50% (DBM‐25, DBM‐50, ZBM‐25 and ZBM‐50 respectively) in the other experimental diets. The experiment lasted 56 days in 1.5 m3 concrete tanks. The results revealed that weight gain and feed conversion ratio (FCR) significantly (p ≤ 0.035 and 0.025 respectively) improved with a polynomial response with a peak at 25% ZBM and a linear increase with DBM up to 50% of FM. Histometric indices of the distal intestine showed improvements (p ≤ 0.001) in villus height, villus width, crypt depth and muscle thickness of fish fed DBM or ZBM compared to the control. In the meantime, there were no histological abnormalities in the liver sections. The replacement of FM with DBM or ZBM could modulated gut bacterial abundance, including total bacterial count, Escherichia coli, Bacillus subtilis, and Lactobacillus sp. The fish‐fed DBM or ZBM‐containing diets had higher (p ≤ 0.05) tolerances to salinity stress than the control group. In conclusion, DBM or ZBM could replace FM up to 50% and 25%, respectively with improved fish growth performance, FCR, gut histology and tolerance to salinity stress. [ABSTRACT FROM AUTHOR]

The current study aimed to evaluate growth performance, digestive enzyme activities, antioxidant status, nonspecific immune response and intestinal histological status of red tilapia fed Daphnia meal (DM) as a substitute for fishmeal (FM). Hybrid red tilapia (Oreochromis mossambicus × Oreochromis aureus) fry (0.54 ± 0.05 g fish−1) was allocated in nylon haba cages (100 fry m−3) for 2 weeks as an acclimation period. The fish were divided into five groups (three replicates each). The experimental diets were prepared by replacing FM with DM at concentrations of 25%, 50%, 75% and 100% respectively. The results indicated that fish fed increasing levels of DM (50%–75%) experienced high growth performance, feed utilisation and protein content. The activities of digestive enzymes were significantly increased in all groups fed DM diets compared to the control. The antioxidant balance was improved by decreasing the level of malondialdehyde and increased the total antioxidant capacity, catalase, superoxide dismutase and glutathione reductase activities in the liver of fish fed DM. The nonspecific immune response, including lysozyme, alkaline phosphatase activities and total protein level improved significantly with increasing FM substitution levels by DM in a dose‐dependent manner. Histometric analysis of the intestinal wall revealed an increase in the villus length, crypts depth and goblet cells number in groups fed DM meal up to 50% substitution level compared to other treatments. It may be concluded from results of this feeding trial that in the aquaculture of hybrid tilapia, FM may be substituted with up to 50% DM without compromising intestinal health, growth performance and immune status of the fish. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of the dietary phytase on growth, feed utilization, body chemical composition, body minerals composition, and effluent phosphorus (P) content in sea bream (Sparus aurata). Treatment 1 (the control group) contained mineral premix (MP) and inorganic phosphorus (IP) (mono-calcium phosphate) at concentrations of 6 g and 5 g kg-1 diet, respectively, without the addition of phytase. The other four treatments contained one level of dietary phytase supplementation at 0.2 g kg-1 (5000 FTU kg), in the presence or absence of MP and IP, separately or in combination, at concentrations of 6 g and 5 g kg-1 diet, respectively. Sea bream (S. aurata) (0.32±0.01 g fish-1) (initial mean weight ± SD) fed the experimental diets for 60 days. Growth and feed utilization were significantly enhanced by dietary phytase-supplemented diets. Final weight, weight gain, average daily gain, specific growth rate, feed intake, and protein efficiency ratio were higher in the phytase-containing treatments than in the control diet, regardless of the presence or absence of monocalcium phosphate or the mineral mixture. Following the same pattern, the feed conversion ratio was better in the phytase-containing treatments than in the control diet. Body crude protein, ash, and mineral composition were significantly increased by the dietary inclusion of phytase regardless of the presence or absence of IP or MM. Furthermore, the addition of phytase into S. aurata diets reduced the phosphorus concentration in their effluents. Thus, this study emphasizes the important role of the dietary phytase in S. aurata in enhancing the growth performance, enriching the body's nutritional composition, and reducing the environmental impacts of fish farming. [ABSTRACT FROM AUTHOR]

Fishmeal (FM) replacement with new cost‐effective protein sources becomes an imperative need for maintaining the continuous and sustainable development of aquaculture. Therefore, the present study investigated the effect of FM substitution with whey protein (WP) on growth, feed utilization, non‐specific immunity, liver and kidney functions, and gut histological status of European seabass, Dicentrarchus labrax, juveniles. A total of 300 seabass juveniles (62.12 ± 0.40 g) were allocated into five treatments (three replicates each) representing 0%, 15%, 30%, 45% and 60% FM substitution by WP. The fish were reared in hapa net‐cages (water volume 0.8 m) and fed the experimental diets for 10 weeks. The results revealed that WP could replace up to 45% of dietary FM without compromising growth, feed utilization and survival. However, the increasing in the substitution level up to 60% significantly decreased all performance criteria of the seabass. The response of seabass to FM replacement with WP in terms of weight gain follows a polynomial regression pattern with R2 = 0.7695. The total immunoglobulin and complement 3 levels in the plasma of seabass significantly improved with a substitution level that ranged between 15% and 30% of FM. The liver function enzymes and kidney function indicators remarkedly increased with increasing WP incorporation levels. The histological investigation of the seabass intestine and liver tissues indicated an increase of histopathological signs with high levels of FM substitution by WP. In conclusion, WP could replace up to 45% of dietary FM in the diet of European seabass juveniles without compromising growth and physiological performance. [ABSTRACT FROM AUTHOR]

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Copyright of Egyptian Journal of Experimental Biology (Zoology) is the property of Egyptian Society of Experimental Biology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)