Evaluation of the Inclusion of the Green Seaweed Ulva ohnoi as an Ingredient in Feeds for Gilthead Sea Bream (Sparus aurata) and European Sea Bass (Dicentrarchus labrax)

Abstract

This study evaluated the use of Ulva ohnoi as an ingredient in feeds for aquaculture in three different experiments. Experiment 1 was oriented to confirm the negative effect of U. ohnoi on fish digestion. Experiment 2 assessed the effect on growth, feed efficiency, and immune status of juvenile sea bass (Dicentrarchus labrax) fed on diets including U. ohnoi, previously treated or not with carbohydrases used to partially hydrolyze indigestible polysaccharides. Experiment 3 was aimed to evaluate the potential protective effect of U. ohnoi on the oxidative status of sea bream (Sparus aurata) challenged by the consumption of a feed formulated with the oil fraction completely oxidized. Results show a negligible effect of U. ohnoi meal on protein digestion when included in feeds at levels of 10% or less. Moreover, results of growth and feed use evidenced the possibility of using up to 5% inclusion of algal meal in feeds without adverse effects on the zootechnical parameters, while the enzyme pretreatment was ineffective to improve its nutritional use. Finally, the inclusion of U. onhoi in feeds determined both an immunostimulatory effect, evidenced by an increase in skin mucus lysozyme in the two mentioned fish species, and a positive influence on the oxidative metabolism of seabream when fed on a diet including rancid oil.

Effect of Dietary Administration of Green Macroalgae (Ulva intestinalis) on Mucosal and Systemic Immune Parameters, Antioxidant Defence, and Related Gene Expression in Zebrafish (Danio rerio)

“…In addition, it has been shown that macroalgae and some products obtained from macroalgae can improve some parameters of innate immune response such as serum lysozyme [ 46 ], alternative complement pathway [ 15 ], and phagocytic activity in cultured fish [ 47 ] and crustaceans [ 10 , 24 ]. Although the exact mechanism is not known, it has been suggested that the effect of macroalgae to increase mucosal immunity may be more than systemic immunity [ 6 ]. Several studies have suggested that macroalgae and their extracts can be used as safer prophylactic and therapeutic alternatives to antibiotics in the control of infectious diseases affecting farmed fish [ 45 ] due to their strong antiviral [ 10 ] and antibacterial properties [ 48 ] against virus and some bacterial fish pathogens [ 9 , 49 ].…”

“…The probiotics [ 1 ], prebiotics, synbiotics, organic acid [ 2 ], and medicinal herb [ 3 ] are among the alternative feed additives which showed beneficial effects in aquaculture [ 4 , 5 ]. Seaweed or seaweed-derived ingredients recieved increasing attention as alternative feed additives in fish feed formulations [ 6 , 7 ], as they are highly nutritious [ 8 ] and have exceptionally versatile properties [ 9 ]. Seaweeds (macroalgae) have widely been used as functional feed additives to improve fish growth [ 10 , 11 ], nutrient utilisation, stress response [ 11 ], fish health, and disease resistance [ 12 ] as well as skin pigmentation in ornamental fish [ 11 ].…”

“…It has been reported that Ulva sp. and its derivatives such as ulvan had immunostimulatory effects and increased disease resistance in various fish and shrimp species [ 23 ], including gilthead sea bream ( Sparus aurata ), European sea bass ( Dicentrarchus labrax ) [ 6 ], Pacific white shrimp ( Litopenaeus vannamei ) [ 10 ], and banana shrimp ( Fenneropenaeus merguiensis ) [ 24 ] diets. On the other hand, different studies have shown that the extracts derived from plants, seaweed, and microalgae can neutralise free radicals in fish tissues and, therefore, can be used as natural sources of antioxidants [ 11 ].…”

Solea senegalensis Bacterial Intestinal Microbiota Is Affected by Low Dietary Inclusion of Ulva ohnoi

“…Although different Ulva species have been applied in several areas, the interest on the potential industrial use of Ulva ohnoi ( Prabhu et al, 2019 ) and its applicability or its products in aquaculture is recent ( Norambuena et al, 2015 ; Fernández-Díaz et al, 2017 ; Martínez-Antequera et al, 2021 ). U. ohnoi is widely distributed and easily grown, with fast growth rates even in recirculating fish farming systems ( Oca et al, 2019 ; Kang et al, 2021 ).…”

“…U. ohnoi is widely distributed and easily grown, with fast growth rates even in recirculating fish farming systems ( Oca et al, 2019 ; Kang et al, 2021 ). Several studies have described effects on the immune system after dietary inclusion of U. ohnoi ( Fumanal et al, 2020 ; Kang et al, 2021 ; Martínez-Antequera et al, 2021 ). In addition, presence of nutraceutical components such as the polysaccharide ulvan has been identified in U. ohnoi extracts ( Fernández-Díaz et al, 2017 ).…”