Aims The objective was to determine the effects of dietary substitution of fishmeal (FM) with live yeast and increasing water temperature on the diversity and composition of gut microbiota in rainbow trout. Methods and Results Fish were fed either FM or yeast (Saccharomyces cerevisiae) and reared in water temperatures of either 11°C (cold) or 18°C (warm) for 6 weeks. Luminal content and mucosa were collected from the distal gut and the load, diversity and species abundance of yeast and bacteria were analysed using agar plating, MALDI-TOF and rRNA gene amplicon sequencing. Yeast in the gut of fish fed FM were represented by S. cerevisiae, Rhodotorula spp. and Debaryomyces hansenii, while fish fed yeast contained 4–5 log higher CFU per g of yeast that were entirely represented by S. cerevisiae. For gut bacteria, sequencing of 16S rRNA gene amplicons using Illumina MiSeq showed lower bacterial diversity and abundance of lactic acid bacteria, especially Lactobacillus, in fish reared in warm rather than cold water. Fish fed yeast had similar bacterial diversity and lower abundance of Leuconostocaceae and Photobacterium compared with fish fed FM. Conclusions Feeding live yeast mainly increased yeast load in the gut, while increased water temperature significantly altered the gut microbiota of rainbow trout in terms of bacterial diversity and abundance. Significance and Impact of the Study Live yeast can replace 40% of FM without disrupting bacteria communities in the gut of rainbow trout, while increased water temperature due to seasonal fluctuations and/or climate change may result in a gut dysbiosis that may jeopardize the health of farmed fish.

The content and composition of prebiotic plant fiber in the diet is important in promoting gut-related health. This study investigated the effects of the dietary inclusion of chicory forage and roots on the intestinal microenvironment of pigs. Thirty-seven-week-old pigs were fed 1 of 5 diets for 18 days, including a cereal-based control diet and 4 diets with the inclusion of 80 and 160 g kg ⁻¹ of body weight chicory forage (CF80 and CF160), 80 g kg ⁻¹ chicory root (CR80), and a mix of 80 g kg ⁻¹ forage and 80 g kg ⁻¹ chicory root (CFR). The animals maintained good performance and health irrespective of diet. Bacterial community structure and diversity in ileal and colonic samples was assessed using terminal restriction fragment length polymorphism (T-RFLP), combined with cloning and sequencing. Samples clustered perfectly according to gut segment with a higher bacterial diversity in colon than ileum. Distal ileum was dominated by lactic acid bacteria (LAB), and the relative amount of this group was increased by the CF160 and CFR diets. The colonic bacterial community was dominated by butyrate-producing bacteria and Prevotella . The increased relative abundance of butyrate-producing bacteria in the colon was positively correlated with the molar proportion of acetic acid and furthermore linked to the chicory forage diets (CF80 and CF160). Diets including chicory roots (CR80 and CFR) were correlated with a higher colonic abundance of Megasphaera elsdenii . The fermentation products and pH in digesta responded to diet type and were correlated with shifts in the microbiota, showing that chicory influences the intestinal microenvironment of pigs.

The rapid growth of aquaculture and scarcity of conventional fish feed supplements has prompted the introduction of new sustainable supplementation sources. In this study, the potential of five strains of fungal biomass of Ascomycetes and Zygomycetes edible filamentous fungi, Aspergillus oryzae, Neurospora intermedia, Rizhopus oryzae, Monascus purpureus, and Fusarium venenatum, cultivated on vinasse, a by-product of the bioethanol industry, as alternative protein sources for fishmeal in the fish diet was evaluated. It was observed that 5% vinasse with an initial pH of 5–6.5 can support fungal biomass yields of 34.3 ± 2.4–118.5 ± 3.9 g DM/L for A. Oryzae, N. intermedia, and R. oryzae. High protein contents of about 44.7%, 57.6%, and 50.9% (w/w), and fat contents of 7.0%, 3.5%, and 5.5% (w/w) were obtained for A. oryzae, N. intermedia, and R. oryzae, respectively. The latter three fungi species contained noticeable amino acid contents, including promising profiles of amino acids that are highly compatible with those of fishmeal. These findings provide evidence that fungal biomasses, with their relatively high protein content, good amino acid profiles, and other essential nutrients, are a promising supplementation alternative that can be produced from low-value by-products and organic-rich waste streams like vinasse to meet the dietary protein requirements in fish feed.

Heat shock proteins (HSPs) are a set of highly conserved proteins that can serve as intestinal gate keepers in gut homeostasis. Here, effects of a probiotic, Lactobacillus rhamnosus GG (LGG), and two novel porcine isolates, Lactobacillus johnsonii strain P47‐HY and Lactobacillus reuteri strain P43‐HUV, on cytoprotective HSP expression and gut barrier function, were investigated in a porcine IPEC‐J2 intestinal epithelial cell line model. The IPEC‐J2 cells polarized on a permeable filter exhibited villus‐like cell phenotype with development of apical microvilli. Western blot analysis detected HSP expression in IPEC‐J2 and revealed that L. johnsonii and L. reuteri strains were able to significantly induce HSP27, despite high basal expression in IPEC‐J2, whereas LGG did not. For HSP72, only the supernatant of L. reuteri induced the expression, which was comparable to the heat shock treatment, which indicated that HSP72 expression was more stimulus specific. The protective effect of lactobacilli was further studied in IPEC‐J2 under an enterotoxigenic Escherichia coli (ETEC) challenge. ETEC caused intestinal barrier destruction, as reflected by loss of cell–cell contact, reduced IPEC‐J2 cell viability and transepithelial electrical resistance, and disruption of tight junction protein zonula occludens‐1. In contrast, the L. reuteri treatment substantially counteracted these detrimental effects and preserved the barrier function. L. johnsonii and LGG also achieved barrier protection, partly by directly inhibiting ETEC attachment. Together, the results indicate that specific strains of Lactobacillus can enhance gut barrier function through cytoprotective HSP induction and fortify the cell protection against ETEC challenge through tight junction protein modulation and direct interaction with pathogens. H.‐Y. Liu, S. Roos, H. Jonsson, D. Ahl, J. Dicksved, J. E. Lindberg, T. Lundh, # Effects of Lactobacillus johnsonii and Lactobacillus reuteri on gut barrier function and heat shock proteins in intestinal porcine epithelial cells {#article-title-2}, Physiol Rep, 3 (4), 2015, e12355, doi: 10.14814/phy2.12355