Probiotics and immunity: a fish perspective.

Thisreviewpresentsanoverviewofantinutritivefac-tors (ANFs) relevant for ¢sh nutrition.The sources ofANFs and the possibilities of reducing the impact ofANFs are brie£y mentioned. Proteinase inhibitors,lectins, saponins and oligosaccharides are given amore thorough presentation regarding mechanismsofactionandthestateof knowledgeregardingeiectson gut function in ¢sh and upper safe dietary levels.Thereafter, selected results from recent works ad-dressing the involvement of T cells and proteinase-activated receptors in soybean-induced enteritis aresummarized. Our conclusions are as follows: we areonlybeginning tounderstandeiects of ANFs in ¢sh;strengthening of the knowledge base is urgentlyneeded to understand the eiects and to ¢nd themeans to overcome or modify these eiects; interac-tions between the eiects of ANFs appear to be veryimportant; the microbiota may modify the eiects ofANFs; not only salmonids are aiected; not only soy-beans contain ANFs of biological importance in ¢sh;andwithincreasedknowledge,wecandevelopbetterdiets for optimal nutrition, health and economy inaquaculture.Keywords: ¢sh,antinutrients,digestivephysiology,immunology,guthealthIntroductionNature has equipped many plants with the ability tosynthesize avarietyof chemical substances withtheapparentfunctionofprotectingthemfrombecomingfood for microbes, insects and higher animals. Con-sequently, many of these compounds may exertharmful eiects when ingested by humans and ani-mals. Such substances are often called antinutritivefactors (ANFs), although they may also have bene¢-cial eiects, such as being antioxidative, immunosti-mulatory or prebiotic, depending on the amountingested.Possibleharmfuleiectsincludereducedpa-latability,lesse⁄cientutilizationoffeednutrientsforgrowth,alterednutrientbalancesofthediets,inhibi-tion of growth, intestinal dysfunction, altered gutmicro£ora, immune modulation, goitrogenesis, pan-creatic hypertrophy, hypoglycaemia or liver damage.The species of animal, its age, size, gender, state ofhealth and plane of nutrition and any stress factorsmaymodifytheseresponses.Inhistextbookontoxicconstituentsofplantfoods,Liener (1980) wrote the following:‘What has only re-cently been realized is that althoughthere might notbe an immediate violent reaction to a certain foodcomponentthere might still beaslowcumulativead-verse eiect resulting in overt disease or less thanop-timal health. This poses a great challenge, sinceknowledge of these eiects is gained slowlyand withdi⁄culty, particularly if the causative principles re-main unidenti¢ed’. Liener’s statement is still validand relevant. During the last10^15 years, inclusionofplantfeedstuisin¢shfeedhasincreasedmarkedlyand consequently so has exposure toANFs. Antinu-tritivefactorsarenoveltomostcultivated¢shspecies,particularly carnivorous species. Fish nutritionistsshould keep in mind Liener’s warning that ‘there

Important antinutrients in plant feedstuffs for aquaculture: an update on recent findings regarding responses in salmonids

The body of work relating to the gut microbiota of fish is dwarfed by that on humans and mammals. However, it is a field that has had historical interest and has grown significantly along with the expansion of the aquaculture industry and developments in microbiome research. Research is now moving quickly in this field. Much recent focus has been on nutritional manipulation and modification of the gut microbiota to meet the needs of fish farming, while trying to maintain host health and welfare. However, the diversity amongst fish means that baseline data from wild fish and a clear understanding of the role that specific gut microbiota play is still lacking. We review here the factors shaping marine fish gut microbiota and highlight gaps in the research.

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The Gut Microbiota of Marine Fish.

Teleost intestinal immunology.

Fish immune system and its nutritional modulation for preventive health care

Soybean meal induces intestinal inflammation in common carp (Cyprinus carpio L.).

This study evaluates the effect of temperature on the development of intestinal disorders when Atlantic salmon are fed soybean meal (SBM). In this study 20% of the dietary fishmeal was replaced by solvent-extracted Hipro SBM. Atlantic salmon reared at two different water temperatures (8 °C and 12 °C), were fed a control diet and an experimental diet for 20 days. Samples were taken at days 7 and 20. The extent of the morphological changes was assessed using a semi-quantitative scoring system developed for this purpose. The study demonstrates that enteritis is affected by temperature. The intestinal disorders were more severe in fish reared at 12 °C compared with those reared at 8 °C. It can be concluded from this study that temperature changes the speed but not the type of SBM-induced enteritis expressed as a delay on the response when Atlantic salmon are kept at lower temperatures.

Soybean meal-induced enteritis in Atlantic salmon (Salmo salar L.) at different temperatures

Soybean meal (SBM) induces enteritis in the distal intestine of Atlantic salmon. The present study assesses the effects of SBM concentrations on the kinetics of the enteritis process. Fish of 300 g, kept at 12 degrees C, were fed diets with different SBM inclusions: 0%, 10% and 20% SBM for 57 days. Samples of the distal intestine of five fish per treatment were taken for histological and electron microscopical analysis. A semi-quantitative scoring system was used to assess the degree of the morphological changes induced by SBM feeding in the distal intestinal epithelium. The first signs of enteritis appeared earlier in the salmon fed the 20SBM diet than in those fed the 10SBM diet. Thereafter, the condition increased steadily, displaying no signs of recovery. Furthermore, at the lower concentration, the process marking the onset of enteritis began more gradually than at the higher concentration and it displayed a tendency to stabilize after 13-20 days of continuous feeding. Electron microscopy indicated that the endocytosis process was hampered at day 3 of 20SBM and at 7 days of 10SBM. Furthermore, a strong reduction of microvilli was already evident after 7 days of 20SBM feeding, thus indicating a decreased uptake capacity of the distal enterocytes. In addition, transformation and migration of eosinophilic granulocytes was observed, which, in combination with the lysozyme C immunoreactivity supports their protective role during the inflammatory process in the distal gut of Atlantic salmon. It can be concluded that the severity of enteritis and its kinetics are concentration-dependent, showing no signs of recovery during feeding with diets containing SBM

Time-related changes of the intestinal morphology of Atlantic salmon, Salmo salar L., at two different soybean meal inclusion levels

Soybean meal (SBM) is a potential alternative for the replacement of fishmeal in aquafeeds. In Atlantic salmon, however, dietary SBM causes an inflammation of the distal intestine, known as SBM-induced enteritis. The objective of the present study is to verify whether different (geographically spread) commercial sources of SBM yield contrasting inflammatory responses. To do so, six SBM batches from different origins were included in the Atlantic salmon diets at the level of 20%. After 4 weeks of feeding, the distal intestine of the salmon was sampled and scored by a semi-quantitative scoring system, which assessed six separated parameters, characterizing the extent of enteritis. The overall mean score as well as the score of the separate parameters varied between the different commercial sources of SBM included in the diet. The variation in SBM caused different degrees of disparity in the score of the separate parameters. The parameter that was most affected by the variation in the source of SBM was the disappearance of supranuclear vacuoles in enterocytes. In contrast, the increase in goblet cells showed the smallest variation between the different SBM sources. This study shows that different commercial sources of SBM can result in differences in the severity of SBM-induced enteritis in Atlantic salmon

Variation in commercial sources of soybean meal influences the severity of enteritis in Atlantic salmon (Salmo salar L.)

Soybean meal-induced enteritis was characterized by the disappearance of the supranuclear vacuoles (SNV) in the enterocytes of the distal intestine of Atlantic salmon Salmo salar. The loss of SNV was correlated with an endocytosis uptake block as shown with ferritin as a marker molecule.

P.A. Urán

Papers

Soybean meal induces intestinal inflammation in common carp (Cyprinus carpio L.).

Soybean meal-induced enteritis in Atlantic salmon (Salmo salar L.) at different temperatures

Time-related changes of the intestinal morphology of Atlantic salmon, Salmo salar L., at two different soybean meal inclusion levels

Variation in commercial sources of soybean meal influences the severity of enteritis in Atlantic salmon (Salmo salar L.)

Brief communication: Soybean meal-induced uptake block in Atlantic salmon Salmo salar distal enterocytes