ABSTRACT
This study investigates the postbiotic potential of extracellular products (ECPs) from Bacillus pumilus strains cultivated on microalgae-supplemented media. We assessed enzymatic and antimicrobial activities to select ECPs that enhance the digestive processes in gilthead seabream. Additionally, we explored the in vitro enzymatic capacity of the chosen postbiotics to hydrolyze macromolecules in microalgae. Finally, a feeding trial was conducted to determine the in vivo effects of the ECPs on Sparus aurata. In vitro enzymatic assays demonstrated diverse hydrolytic capacities among ECPs. All conditions exhibited antimicrobial activity against Photobacterium damselae subsp. piscicida, with variation in inhibitory effects against Vibrio harveyi and Tenacibaculum maritimum. Furthermore, in vitro assays revealed differences in protein hydrolysis and soluble protein concentration, influencing amino acid and reducing sugar release from microalgal biomass. These analyses facilitated a selection to test ECPs in vivo. Lastly, the in vivo experiment revealed no differences in the growth performance, nutrient utilization, and general metabolism of S. aurata fed the experimental diets. Dietary inclusion of postbiotics increased the activity of key digestive enzymes in fish compared to the control group, and particularly, values increased significantly when the fish were fed with the ECP-nanoparticulate-supplemented diet. In conclusion, the inclusion of microalgae in the culture media significantly influences the activity of extracellular products from B. pumilus strains, as evidenced in both in vitro and in vivo assays.
ABSTRACT
Fishmeal and fish oil have been the main sources of protein and fatty acid for aquaculture fish. However, their increasing price and low sustainability have led the aquafeed industry to seek sustainable alternative feedstuffs to meet the nutritional requirements of fish and improve their health and performance. Plant proteins have been successfully used to replace fishery derivatives in aquafeeds, but the presence of anti-nutritional substances is a potential drawback of this approach. Thus, it has been reported that phytate breakdown can be caused by feed supplementation with exogenous phytase. The inclusion of microalgae has been proposed to improve gut functionality in fish fed diets with a high vegetable protein content. The aim of this study was to evaluate the effect on the growth and gut microbiota of European seabass (Dicentrarchus labrax) juveniles of a diet containing a blend of microalgae (Arthrospira platensis and Nannochloropsis gaditana) and different concentrations of phytase. An 83-day feeding trial was conducted, comprising four experimental diets with 2.5% microalgae and 500, 1,000, 2,000, or 10,000 phytase units (FTU)/kg feed and a microalgae- and phytase-free control diet. At the end of the trial, a significantly increased body weight was observed in fish fed the diet with the highest phytase concentration (10,000 FTU/kg) versus controls, although the gut bacterial composition did not differ from controls in alpha or beta diversity with either majority (Weighted UniFrac) or minority bacterial strains (Unweighted UniFrac). In comparison to the control group, the groups fed diets with 1,000 or 2,000 FTU/kg diets had a lower alpha diversity (Shannon's diversity index), while those fed diets with 500 FTU/kg or 1,000 FTU/kg showed distinct clusters in beta diversity (involving minority ASVs). According to these findings, the diet containing the 2.5% microalgae blend with 10,000 FTU/kg may be useful to increase the aquafeed quality and sustain the growth performance of juvenile European seabass.
Subject(s)
6-Phytase , Animal Feed , Bass , Dietary Supplements , Gastrointestinal Microbiome , Microalgae , Animals , 6-Phytase/metabolism , Bass/growth & development , Bass/metabolism , Gastrointestinal Microbiome/drug effects , Animal Feed/analysis , Aquaculture/methodsABSTRACT
Tenebrio molitor (TM) is considered as one of the most promising protein sources for replacing fish meal in aquafeeds, among other things because it is rich in protein, a good source of micronutrients and has a low carbon footprint and land use. However, the main drawback of TM is its fatty acid profile, in particular its low content of n-3 PUFA. This study evaluates the effects of partially replacing plant or marine-derived with full-fat TM meal at two different levels on growth performance and lipid profiles of Senegalese sole (Solea senegalensis). For this purpose, a control diet (CTRL) and four experimental isoproteic (53%) and isolipidic (16%) diets were formulated containing 5 and 10% TM meal replacing mostly fish meal (FM5 and FM10), or 10 and 15% TM meal replacing mostly plant meal (PP10 and PP15). Fish (215 g) were fed at 1% of their body weight for 98 days. The final body weight of fish fed the experimental diets containing TM meal was not different from that of fish fed the CTRL diet (289 g). However, the inclusion of TM meal resulted in a gradual improvement in growth rate and feed efficiency in both cases (replacement of fish or plant meals), and significant differences in specific growth rate (SGR) were observed between fish fed the CTRL diet (SGR = 0.30% day-1) and those fed diets with the highest TM meal content (PP15; SGR = 0.35% day-1). The experimental groups did not show any differences in the protein content of the muscle (19.6% w/w). However, significant differences were observed in the total lipid content of the muscle, with the FM10, PP10, and PP15 groups having the lowest muscle lipid contents (2.2% ww). These fish also showed the lowest neutral lipid content in muscle (6.6% dw), but no differences were observed in the total phospholipid content (2.6% dw). Regarding the fatty acid profile, fish fed FM10, PP10 and PP15 had lower levels of linoleic acid (18:2n-6) and higher levels of oleic acid (18:1n-9) in liver and muscle compared to fish fed CTRL. However, no differences were found between fish fed CTRL and TM-based diets for docosahexaenoic acid (22:6n-3) and total n-3 PUFA in liver and muscle. In conclusion, our study demonstrated that full-fat TM inclusion up to 15% in S. senegalensis diets had no negative effects or even some positive effects on fish survival, growth performance, nutrient utilization and flesh quality.
ABSTRACT
Resumen El pejelagarto es una especie importante para la acuicultura en el sureste de México. Se han realizado varios estudios sobre nutrición y fisiología digestiva; sin embargo, el uso de microcápsulas para la alimentación de larvas que permitan mejorar el crecimiento y la supervivencia no ha sido realizado. En este sentido, se evaluaron cuatro alimentos microencapsulados en el crecimiento y supervivencia de larvas de pejelagarto (Atractosteus tropicus). Los tratamientos consistieron en cuatro dietas experimentales y un control: 1) Microcápsula con base en harina de pescado (DP), 2) Microcápsula con base en una combinación de harina de cerdo y pollo (Re), 3) Microcápsula con base en Nannochloropsis gaditana (Ng), 4) Microcápsula con base en un preparado enzimático, pancreatina (PE) el tratamiento control 5) Nauplios de Artemia (Na). Los resultados de las dietas indican que las larvas alimentadas con Nauplios (Na) tuvieron el mayor crecimiento y supervivencia (3.93 cm, 0.19 g y 82 % respectivamente). Mientras que en el caso de las larvas alimentadas con las dietas microencapsuladas, los mejores valores de supervivencia se observaron con las dietas Nannochloropsis gaditana (Ng) y preparado enzimático (PE) (20.0 y 19.2 % respectivamente). Nuestros resultados demuestran que el uso de microencapsulados para la alimentación de larvas de A. tropicus es factible, aunque se requieren más investigaciones para optimizar su diseño y elaboración para mejorar el crecimiento y supervivencia de los organismos.
Abstract Tropical gar is an important species for aquaculture purposes in Southeast Mexico. Several studies regarding nutrition and digestive physiology have been done; however, the use of microcapsules for larvae feeding to improve growth and survival has not been conducted. In this sense, four microencapsulated diets were evaluated with respect to the growth and survival of tropical gar Atractosteus tropicus larvae. The treatments consisted of four experimental diets and one control diet 1) fish meal, 2) a combination of pork and poultry meals, 3) Nannochloropsis gaditana meal, 4) enzyme preparation and the control treatment 5) Artemia nauplii. The evaluation indicated that the larvae fed the Artemia nauplii obtained the greatest growth and survival (3.93 cm, 0.19 g y 82 % respectively), which justifies a correct culture system operation. While larvae fed microencapsulated diets best values in survival were observed with diets Nannochloropsis gaditana and enzyme preparation (20.0 and 19.2 %). Our results showed that microencapsulated could be used to feed A. tropicus in feasibly form. However, more information concerning to optimize the design and manufacturing are required to improve the growth and survival of organisms. Rev. Biol. Trop. 66(3): 1298-1313. Epub 2018 September 01.