“Does timing matter: effects of β-glucan supplementation duration on the gut microbiome and health of juvenile nile tilapia (7245)”

does timing matter: effects of β-glucan supplementation duration on the gut microbiome and health of juvenile nile tilapia

supplementing fish diet with prebiotics, e.g., β-glucans, has been used as an alternative to antibiotic treatment to boost the non-specific immune system and modulate the gut microbiota profile, thereby enhancing gut mucosal health and improving resistance against diseases. however, such benefits are mostly studied from older fish, and little is known on early life stages. in this study, we aimed to evaluate the effects of β-glucan supplementation periods during early-life feeding of nile tilapia (oreochromis niloticus) on growth performance, gut microbiota profile, and the regulation of immune responses.

we fed 10-day-old nile tilapia with six diet combinations over a period of six weeks by switching between a diet containing insoluble β-glucans—at low-(l) or high-(h) concentration—and a control diet (c), without supplementation. the diet was switched after the first two weeks (lcc, lcl, clc, hcc), or the fish were fed the same diet throughout the experiment (ccc, lll). gut samples were collected every two weeks and used for dna and rna extraction to analyze gut microbiota profile and immunomodulation, respectively. gut microbiota profile was assessed using oxford nanopore technology sequencing, targeting full-length 16s-rrna genes. immunomodulation was assessed by measuring the relative expression of cytokine genes (il1b, tnfa, ifnγ, il10, il12p40) and tight junction protein (tjp) genes (claudin3 and marveld) using rt-qpcr. following the feeding trial, fish were immune-challenged with inactivated streptococcus iniae for 48h, after which the expression of cytokine and tjp-genes was analyzed.

our results showed no significant effects of supplementation on fish growth. we also found no effects of supplementation on gut microbial diversity at the end of feeding trial. however, regardless of the administration protocol, we observed an increased abundance of potential fermentative bacteria (romboutsia and paraclostridium) in all β-glucan-fed groups. the ongoing 16s-rrna sequencing analyses of gut samples collected at week 2 and 4 are expected to provide further understanding how different administration protocols alter gut microbiota composition. following the immune challenge with inactivated bacteria, we observed a downregulation of expression of the cytokine il1b and tjp marveld genes in fish from the lll and hcc groups, suggesting that continuous supplementation, or short high-dose exposure, may induce more pronounced effects.

finally, our results underscore the potential of β-glucans supplementation in modulating gut microbiota of juvenile tilapia towards beneficial taxa and suggest that different administration protocols can lead to different patterns of expression of health-related genes, although further (ongoing) analysis is needed to support these conclusions.

1. FINO, HANISWITA AMRIZAL, WAGENINGEN UNIVERSITY, Presenter
2. WIEGERTJES, GEERT F, WAGENINGEN UNIVERSITY, Author
3. KOKOU, FOTINI, WAGENINGEN UNIVERSITY, Author