Cao, Shuowen
- Department of Applied Animal Science and Welfare, Swedish University of Agricultural Sciences
Abstract
Aquaculture is the fastest-growing food production sector globally and plays a crucial role in ensuring future food security. However, sustainable intensification of aquaculture requires novel feed ingredients and strategies that promote fish health and performance while reducing dependence on conventional protein sources such as fishmeal and soy. The gut microbiota represents a key biological interface between diet, host physiology, and environmental factors, profoundly influencing nutrient utilization, immune function, and overall fish wellbeing. This thesis examined the influence of biotic, abiotic, and particularly dietary factors on the intestinal microbiota of salmonid species, with a specific focus on rainbow trout (Oncorhynchus mykiss), and the potential of microbial-based feed ingredients to support sustainable aquaculture.
The first study applied a meta-analytical approach to integrate data from published sequencing studies on Atlantic salmon and rainbow trout. The analysis revealed that the gut microbiota composition of salmonids is strongly influenced by methodological, environmental, and host-related factors, underscoring the need for standardization in sampling and sequencing protocols.
The second study evaluated four filamentous fungi, Aspergillus oryzae, Neurospora intermedia, Rhizopus delemar, and Rhizopus oryzae, grown on ethanol-production stillage as alternative protein sources in rainbow trout diets. While these fungal biomasses exhibited comparable but slightly lower digestibility scores compared with the control, their inclusion altered intestinal microbial diversity, highlighting their potential as sustainable feed ingredients pending improvements in digestibility.
The third study assessed the effects of dietary supplementation with two yeast probiotics, Kluyveromyces marxianus and Rhodosporidium babjevae, on rainbow trout gut microbiota, immune-related gene expression, and growth performance. Supplementation with R. babjevae modulated the abundance of beneficial bacterial taxa and influenced immune-related gene expression, supporting its candidacy as a promising probiotic for aquaculture feeds.
Collectively, this work advances the understanding of how feed composition and microbial inputs affect the gut ecosystem of farmed salmonids. The findings contribute to the development of more sustainable and health-promoting aquafeed formulations, facilitating the transition toward environmentally responsible aquaculture practices.
Keywords
16S rRNA gene sequencing; fresh water; gut bacteria; microbiome; salmonid; filamentous fungi; yeast probiotic; nutrient digestibility; immunity; 16S rDNA; sötvatten; tarmmikrober; mikrobiom; laxfiskar; filamentösa svampar; jästprobiotika; näringsupptag; immunförsvar
Published in
Acta Universitatis Agriculturae Sueciae
2025, number: 2025:91
Publisher: Swedish University of Agricultural Sciences
SLU Authors
UKÄ Subject classification
Animal and Dairy Science
Fish and Aquacultural Science
Microbiology
Publication identifier
- DOI: https://doi.org/10.54612/a.6jl5jv1vb3
- ISBN: 978-91-8124-075-7
- eISBN: 978-91-8124-121-1
Permanent link to this page (URI)
https://res.slu.se/id/publ/142492