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The effects of cyclical feeding restriction (3, 4, 5, 6, and 7 days of feeding per week) on the performance of juvenile Nile tilapia (Oreochromis niloticus) in a biofloc technology system (BFT) were evaluated in this study for 77 days. Fifteen experimental units (400L) with temperature control (mean 28.2 °C) randomly distributed 1500 fish (0.42 ± 0.02 g). Fish were fed commercial feed (46.7 g of crude protein and 4475.5 kcal kg−1 of gross energy) up to satiation. Feeding cycles with different restrictions (p < 0.05) influenced animal growth but not survival and final density (p > 0.05), which remained around 94% and 235 fish.m−3, respectively. Juveniles fed 6 days a week showed 1.25 of feeding efficiency, while animals fed 3 days a week (more restricted) showed hyperphagia but did not exhibit compensatory growth. Changes in the morphology of hepatocytes (presence of vacuoles, displacement of the nucleus to the periphery, and fatty degeneration) were observed with an increase in feeding days, and a high degree of hepatic steatosis (p < 0.05). Water quality parameters remained within acceptable limits for the species and system operation. Feeding regimes influenced the characteristics of bioflocs (total suspended solids and porosity) and the abundance of microorganisms (p < 0.05). Nutritionally, less restricted diets (6 and 7 days of feeding per week) produced more protein (38.3 and 40.6% CP) and energy bioflocs (2252.8 and 2313 kcal.kg−1) (p < 0.05), while protein, lipid, and body energy were significantly lower (p < 0.05) with the more restricted diet. The composition of microorganisms was influenced by the feeding regimes (p < 0.05). Results demonstrated that the occurrence of total compensatory growth (6 days of feeding per week) represents an economic advantage with a reduction of 26.8% of feed and greater profitability in the unitary commercialization of tilapia juveniles. [ABSTRACT FROM AUTHOR]

Phosphorus is an essential mineral present in the vegetable matter in the form of phytate, which is considered an antinutritional factor. Phytate can be degraded by phytases, which have been used in commercial feeds. However, these enzymes undergo costly isolation and purification processes. In the present study, a genetically modified (GM) Bacillus subtilis strain that expresses a fungal phytase was used as a feed additive. The GM probiotic was added to the commercial feed of shrimp Litopenaeus vannamei and its effects on zootechnical performance, proximate composition of muscle, lipid concentration in hepatopancreas, and expression of genes related to digestion, amino acid metabolism, and antioxidant defenses were analyzed. Although the genetically modified probiotic had no impact on growth parameters, there was a 39% increase in phosphorus content in muscle. In addition, genes related to digestion were downregulated in shrimp hepatopancreas, as well as an increase in lipids in this tissue. These results demonstrate that the GM probiotic increased the efficiency of the use of plant-derived phosphorus, which may imply a decrease in the addition of this element in the diets, as well as minimizing the impact of shrimp farms on the eutrophication of adjacent ecosystems. [ABSTRACT FROM AUTHOR]

Filamentous fungi, mainly those belonging to genera Aspergillus, Fusarium, and Penicillium, the main producers of mycotoxins and responsible for food and feed contamination, exhibit metabolites that are highly toxic to animals and humans. This scoping review compiles data on occurrence of mycotoxins in fish feed, assesses distribution of metabolites across continents by the hierarchical cluster analysis, and establishes risks posed to the main global orders of farmed fish by exposure to mycotoxins. Resulting data showed that fish of different orders in both fingerling and juvenile phases are exposed to high concentrations of mycotoxins. [ABSTRACT FROM AUTHOR]

Cyanobacteria are a rich source of nutrients in addition to producing bioactive compounds capable of stimulating the immune system of hosts. Also, they can be manipulated with relative ease to produce heterologous proteins. In the present study, a strain of Synechococcus elongatus (PCC7942) was manipulated to produce a prokaryotic β-glucosidase. This strain was added to the diet of Pacific white shrimp Litopenaeus vannamei for 45 days and parameters such as growth performance, proximate composition of muscle tissue and expression of genes related to digestion, amino acid metabolism, immune system and antioxidant defenses were evaluated. Histology of shrimp hepatopancreas was also performed. Transgenic cyanobacteria did not produce negative effects on shrimp growth performance. Regarding proximate composition, an increase in lipid and phosphorus deposition was observed in the muscle of shrimp, as well as lipid in hepatopancreas. Furthermore, an increase in expression of genes related to the immune system (tgase) as well as carbohydrate metabolism and amino acid metabolism (gdh) was observed. It was observed also that both strains of cyanobacteria (wild and transgenic) produced effects on carbohydrate metabolism (increased amy expression) and digestive system (decreased cathB expression). It is possible that cyanobacteria in the diet may be serving as a source of carbohydrates, reducing the use of proteins as a source of energy. It can be concluded that transgenic cyanobacteria had a beneficial effect on shrimp by increasing lipid deposition in muscle and hepatopancreas as well as phosphorus absorption from feed, which can minimize the environmental impact of shrimp farms. [ABSTRACT FROM AUTHOR]

Bioaccessibility of aflatoxin B1 (AFB1) found in contaminated peanut meal was assessed by an in vitro system that simulated conditions of Nile tilapia (Oreochromis niloticus) intestine. Peanut meal containing 17.1 µg kg−1 AFB1 was used as substrate. Reference assays were carried out with intestinal enzyme extracts from adult tilapia under realistic physiological conditions of enzyme/substrate ratio (0.21 U mg−1), pH (8.2), and temperature (25 °C). Different factors that could potentially affect bioaccessibility of AFB1 were evaluated: total digestion time (3 to 6 h), relative amount of substrate (250 to 750 mg), and amount of rice husk used as adsorbent (1:1 and 1:2, peanut meal/rice husk). AFB1 released after digestive hydrolysis was extracted by QuEChERS and quantified by a multi-reader. Bioaccessibility of AFB1 increased with digestion time (from 36 after 3 h to 100% after 6 h) and with the amount of substrate. In contrast, rice husk reduced bioaccessibility of AFB1 by 28 and 20% in ratios of 1:1 and 1:2, respectively. Therefore, this study suggests not only that in vitro assays may be used as prospective assays to evaluate bioaccessibility of AFB1 under species-specific digestive conditions, but also that inclusion of rice rusk in feed may be a promising tool to reduce mycotoxin bioaccessibility. [ABSTRACT FROM AUTHOR]

The addition of pure carotenoids is a common practice in some aquaculture species production since its use in fish feed is known to improve carcass and antioxidant capacity. Spirulina (Arthrospira) cyanobacteria are a rich source of carotenoids that has proven health benefits for fish welfare. In the current experiment, four isonitrogenous (38%) isolipidic (9%) diets were made, including a control diet (free of β-carotene and Spirulina, SP0), β-carotene diet (50 mg kg−1, β0), and two Spirulina (Arthrospira platensis) diets with 2% (SP2) and 4% (SP4) of total feed inclusion. The experimental diets were given to juvenile mullets in a controlled recirculation system. The parameters evaluated were growth, colour, total carotene content of muscle, and antioxidant capacity of the liver and muscle. Significant differences were found (p < 0.05) in the final weight, specific growth rate, and feed conversion ratio between the SP0 treatment and the β0, SP2, and SP4 treatments. The colorimetric analysis showed that the redness and carotene deposition in muscle of mullet is statistically the same between β0 and SP4. Mullets fed with Spirulina (SP2 and SP4 treatments) had a statistical higher antioxidant capacity against radical peroxyls in liver tissue, showing lower lipid peroxidation (TBARS). In conclusion, Spirulina can be a suitable substitute for pure β-carotene addition in fish diets, improving some of the health benefits from this carotene. [ABSTRACT FROM AUTHOR]