Fish Microbiome Modulation and Convenient Storage of Aquafeeds When Supplemented with Vitamin K1

Vitamin K (VK) is a fat-soluble vitamin necessary for fish metabolism and health. VK stability as dietary component during aquafeed storage and its potential effect on intestinal microbiome in fish have not yet been completely elucidated. The convenient storage conditions of aquafeeds when supplemented with phylloquinone (VK1), as well as its potential effects on the gut microbiota of Senegalese sole (Solea senegalensis) juveniles, have been explored. Experimental feeds were formulated to contain 0, 250 and 1250 mg kg−1 of VK1 and were stored at different temperatures (4, −20 or −80 ◦C). VK stability was superior at −20 ◦C for short-term (7 days) storage, while storing at −80 ◦C was best suited for long-term storage (up to 3 months). A comparison of bacterial communities from Senegalese sole fed diets containing 0 or 1250 mg kg−1 of VK1 showed that VK1 supplementation decreased the abundance of the Vibrio, Pseudoalteromonas, and Rhodobacterace families. All these microorganisms were previously associated with poor health status in aquatic organisms. These results contribute not only to a greater understanding of the physiological effects of vitamin K, particularly through fish intestinal microbiome, but also establish practical guidelines in the industry for proper aquafeed storage when supplemented with VK1

Stressors Due to Handling Impair Gut Immunity in Meagre (Argyrosomus regius): The Compensatory Role of Dietary L-Tryptophan

In the context of intensive aquaculture, meagre (Argyrosomus regius) is one of the most important new aquaculture species in Southern Europe and several studies are focused on the optimization of its culture. Nevertheless, stressors such as handling during transport or culture maintenance may affect the immune system, thereby impairing some immune responses or provoking cellular damage. One strategy that has been used to avert this type of negative stress response is the supplementation of amino acids to improve resistance to stress. In this experiment, meagre (105.0 ± 2.6 g, mean ± standard deviation) juveniles were fed two diets for a period of 7 days, the first a commercial diet supplemented with 1% tryptophan (Trp) and second, the same commercial diet without tryptophan supplementation (control group). The effects of two types of handling stressors (air exposure and confinement/netting) on fish fed both diets was evaluated in terms of gene expression of the selected gut immunity markers, such as (1) innate immune response processes: c3 complement (c3), lysozyme (lys), and cyclooxygenase (cox2); (2) humoral immune response processes: interferon type 1 (ifn1), mx protein (mxp), interleukin 1b (il-1b), tumor necrosis factor 1a (tnf1a), and interleukin 10 (il-10); (3) antimicrobial peptides: defensin (def), hepcidin (hep), piscidin (pis), and a marker for mitochondrial respiration: glyceraldehyde 3-phosphate dehydrogenase (gapdh). Samples of the anterior intestine were collected at 1 and 6 h post-stress (hps). Results showed that in fish fed 1% Trp, the air exposure resulted in an upregulation of gene expression at 6 hps for c3, lys, cox2, ifn1, mxp, il-10 and gapdh, and il-1b and pis. The confinement/netting test for fish fed 1% Trp resulted in an upregulation of c3 and mxp and a downregulation of cox2, ifn1, il-1b, tnf1a, il-10, def, hep, and gapdh at both post-stress times (1 and 6 hps). According to the present study, dietary supplementation with 1% Trp may be considered as a proper nutritional strategy for improving tolerance and/or alleviating acute response to handling stressors

Dietary Debaryomyces hansenii promotes skin and skin mucus defensive capacities in a marine fish model

The present study explores the effects of two supplementation levels of Debaryomyces hansenii (1.1% and 2.2%) as a probiotic in a reference low fish meal-based diet on the skin mucosal tissue in Sparus aurata. This study includes the evaluation of fish performance coupled with a holistic study of the skin mucosa: i) a transcriptomic study of the skin tissue, and ii) the evaluation of its secreted mucus both in terms of skin mucosal-associated biomarkers and its defensive capacity by means of co-culture analysis with two pathogenic bacteria. Results showed that after 70 days of diet administration, fish fed the diet supplemented with D. hansenii at 1.1% presented increased somatic growth and a better feed conversion ratio, compared to fish fed the control diet. In contrast, fish fed the diet including 2.2% of the probiotic presented intermediate values. Regarding gene regulation, the probiotic administration at 1.1% resulted in 712 differentially expressed genes (DEGs), among which 53.4% and 46.6% were up- and down-regulated, respectively. In particular, D. hansenii modulated some skin biological processes related to immunity and metabolism. Specifically, D. hansenii administration induced a strong modulation of some immune biological-related processes (61 DEGs), mainly involved in B- and T-cell regulatory pathways. Furthermore, dietary D. hansenii promoted the skin barrier function by the upregulation of anchoring junction genes (23 DEGs), which reinforces the physical defense against potential skin damage. In contrast, the skin showed modulated genes related to extracellular exosome and membrane organization (50 DEGs). This modulated functioning is of great interest, particularly in relation to the increased skin mucus defensive capacity observed in the bacterial co-culture in vitro trials, which could be related to the increased modulation and exudation of the innate immune components from the skin cells into the mucus. In summary, the modulation of innate immune parameters coupled with increased skin barrier function and cell trafficking potentiates the skin's physical barrier and mucus defensive capacity, while maintaining the skin mucosa's homeostatic immune and metabolic status. These findings confirmed the advantages of D. hansenii supplementation in low fish meal-based diets, demonstrating the probiotic benefits on cultured marine species

Effect of diets supplemented with different seaweed extracts on growth performance and digestive enzyme activities of juvenile white shrimp Litopenaeus vannamei

International audienceThis study evaluated the nutritional potential of three seaweed extracts (Ulva lactuca, Eisenia sp. and Porphyra sp.) as possible ingredients in shrimp feed to improve growth and main digestive enzyme activities. Seaweed extracts were included in replacement of wheat and soybean meal in isoproteic diets (35 +/- 0.5%) at three levels of inclusion (5, 10, and 15%) and tested during 28days in a feeding trial on Litopenaeus vannamei (initial weight 1.15 +/- 0.08g). Growth performance and feed utilisation parameters, in addition to trypsin, chymotrypsin, lipase and amylase activities, were evaluated. An increase of ash content in experimental diets was observed as seaweed extract inclusion level increased (from 7 up to 13.4%). All shrimps fed with seaweed diets significantly improved (p<0.01) final weight (FW), weight gain (WG), specific growth rate (SGR) and feed intake (FI) in contrast to control diet. In general, Ulva diets presented the best shrimp growth performance, among which inclusion of 15% Ulva extract resulted in significantly higher FW, WG and SGR (p<0.01) compared to control, Porphyra and Eisenia diets. In the case of chymotrypsin, lipase and amylase enzyme activity, a significant interaction between seaweed type and inclusion level was found (p<0.01), where in most cases, inclusion level of 5% of all type of seaweed resulted in an increase of the enzyme activities. The use of any of the three proposed seaweed extracts in balanced feed, especially Ulva, is suggested to promote shrimp growth productivity

Influence of dietary live yeast on European sea bass (Dicentrarchus labrax) larval development

International audienc

Carta Acuícola Iberoamericana

Trabajo realizado por investigadores de la Red LARVAplus y colaboradores. El mismo constituye un compendio sobre la información disponible de gran parte de especies autóctonas de peces que se cultivan en Iberoamérica, información que tiene como objetivo servir como referencia para instituciones públicas, universidades, centros de investigación, emprendedores y sector productivo para establecer sus programas y planes de desarrollo acuícola