engleski

The effect of black soldier fly Hermetia illucens crude protein and Bacillus spp. supplementation on gilthead sea bream (Sparus aurata) intestinal health status

Introduction: In an era of rising antimicrobial resistance and overfished stocks, aquaculture strives to find cost-effective and environmentally-friendly alternatives for fish meal and chemotherapeutics, while meeting the market demand for high-quality fish products. Use of alternative protein sources and health-promoting additives, such as insect-derived proteins and probiotics, has beneficial effects on fish health at both local and systemic level, although the involved mechanisms are largely unknown. Methodology: We performed a six-month farm feeding trial with three groups of gilthead sea bream (Sparus aurata) in duplicate cages using i) feed supplemented with insect protein ; ii) feed supplemented with insect protein plus autochthonous intestinal Bacillus spp. ; and iii) standard feed (control). For the second treatment group, feeding regime during the whole six-month trial included 2-weeks of Bacillus-supplemented diet administration followed by 2-weeks of feed administration where insect meal was included, i.e. the same diet used for the first treatment group. Twelve fish per treatment group were sampled at 0.5, 1 and 6 months after the start of the trial. Samples were collected for whole-intestine microbiota analysis (MiSeq 16s rRNA), histological analysis (TEM) and gene expression analysis using a customized PCR-array of 44 selected markers of intestinal function and integrity, nutrient transport, and immune response. Results: Intestinal epithelium of all treatment groups showed no signs of degenerative or inflammatory changes. Main changes in microbial community composition occurred already within the first month of feeding trial. PLS discriminant analysis of gene expression in respect to the dietary treatment allowed the selection of 17 genes, mostly related to epithelia integrity and immune response that showed high contribution to differences among diets. Heatmap clustering of the selected genes grouped together the experimental diets apart from the control diet. Many of the epithelia integrity markers were up-regulated with insect diet, and probiotic supplementation additionally amplified this up-regulation. Probiotic also reversed the up-regulation of inflammatory/immune-regulatory genes that occured with insect diet. Conclusions: In conclusion, probiotic supplementation emerges as beneficial for the preservation of gut homeostasis and innate immunity in fish fed alternative protein sources.

probiotics ; Bacillus spp. ; Hermetia illucens ; black soldier fly ; gilthead sea bream ; Sparus aurata

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