Health status in gilthead seabream (Sparus aurata) juveniles fed diets devoid of fishmeal and supplemented with Phaeodactylum tricornutum

Abstract

To enhance fish general health, feeds can be supplemented with health promoting additives, reducing the need to use chemotherapeutics. Incorporation of marine algae biomasses in aquafeeds has been shown to improve fish immune status by enhancing innate immune response. This study intended to evaluate the effects of microalgae Phaeodactylum tricornutum incorporation in feed by two different processes, either as freeze-dried biomass or broken cell wall biomass, on fish health status and performance.Triplicate groups of gilthead seabream juveniles (13.3 ± 0.3 g) were either fed a control diet (CTRL) with an extreme (i.e. 0 % fishmeal), nutritionally balanced, formulation, or two experimental diets formulated as the CTRL with 1 % inclusion of P. tricornutum at the expense of wheat meal: BC diet contains P. tricornutum broken cells and WC diet microalgae whole cells. After 2 and 12 weeks of feeding, blood was collected for haematological procedures whereas plasma and mucus were sampled for immune parameters. Head-kidney, liver and white skeletal muscle were also collected for gene expression measurements.Mucus bactericidal and alternative complement pathway activity increased when seabream juveniles were fed BC diet for 2 and 12 weeks, respectively. No major differences were observed in haematological nor plasma humoral parameters after 12 weeks irrespective of dietary treatment. Arrays of 29-31 genes were analyzed in the different tissues, revealing an early dietary effect (2 weeks) in a tissue-specific pattern.In liver, the major effect was found in the GH/IGF axis and in muscle there was a late down-regulation of myostatin (mstn) gene, mainly due to WC diet, even though all fish had similar growth performance. Regarding the head-kidney, BC diet led to interleukin 6 (il-6) and alpha-2-macroglobulin (a2m) gene up-regulation. Hence, it seems that BC diet has a potential stimulatory effect that might be relevant as a prophylactic measure before a predictable stressful event.

Cross-Talk Between Intestinal Microbiota and Host Gene Expression in Gilthead Sea Bream (Sparus aurata) Juveniles: Insights in Fish Feeds for Increased Circularity and Resource Utilization

“…Fish production continues to be strongly dependent on FM (Ytrestøyl et al, 2015 ; Hua et al, 2019 ), but there is now evidence that the use of a combination of plant proteins, poultry meal, and insect proteins is able to support optimal growth in a wide range of farmed marine fish, such as gilthead sea bream (Basto et al, 2021 ; Reis et al, 2021 ). Moreover, there is now evidence that the reshaping of gut microbiota by the replacement of FM with poultry meal and microbial biomass would serve to exert an adaptive and counter-regulatory inflammatory action at the local intestine level (Solé-Jiménez et al, 2021 ).…”

“…In the same line, antioxidant extracts of Gracilaria protected against oxidative stress, improving the stress resilience of gilthead sea bream during acute hypoxia (Magnoni et al, 2017 ). Moreover, the supplementation of FM-free diets with marine diatomeas ( Phaeodactylum tricornutum ) stimulated the immune system of gilthead sea bream, which might be relevant as a prophylactic measure before predictable stressful events (Reis et al, 2021 ). Additionally, algae or algae-based products are currently used to replace or reduce the inclusion level of fish oil (FO) in aquafeeds, assuring the dietary supply of n-3 polyunsaturated fatty acids to meet the nutritional requirements of fish, as well as the healthy value of seafood products for human consumption (Maldonado-Othón et al, 2020 ; Pereira et al, 2020 ).…”

Chitosan-Based Sustained Expression of Sterol Regulatory Element-Binding Protein 1a Stimulates Hepatic Glucose Oxidation and Growth in Sparus aurata

“…The formulation of sustainable aquafeeds through the partial substitution of fishmeal by microalgae and a combination of plant-and animal-derived protein, such as soybean and poultry by-product meals, is the subject of intense research [21][22][23][24][25]. However, the substitution of fishmeal and dietary protein with cheaper nutrients with less environmental impact is a challenging issue due to the metabolic features of fish, particularly carnivorous fish, such as S. aurata.…”

Reshaping of Gut Microbiota in Gilthead Sea Bream Fed Microbial and Processed Animal Proteins as the Main Dietary Protein Source

“…(B) Heatmap representing the abundance distribution (Z-score) of the OTUs identified to be driving the separation by diet among all groups. -Pinto et al, 2019;Reis et al, 2021). Among these strategies, PAP and SCP are promising materials to develop future fish feeds.…”