ORCID
- Sherilyn Abarra: 0009-0007-9482-3882
Abstract
To address the need for well-characterised probiotic strains for tilapia and carp aquaculture, this study investigated the isolation, characterisation, and application of host-derived candidate probiotics from Nile tilapia (Oreochromis niloticus) and mirror carp (Cyprinus carpio), and their influence on growth, feed utilisation, intestinal integrity and microbiome, and mucosal health of the host.A total of 263 intestinal bacterial isolates were screened in vitro for antagonism against Aeromonas hydrophila and Streptococcus iniae. The top 31 isolates with inhibitory effects underwent screening against three further fish pathogens and were assessed for haemolytic activity and extracellular enzyme production in vitro. Isolates C61 and T70, demonstrated superior probiotic traits and were identified as strains of Bacillus subtilis. Both retained over 85% of their pathogen antagonism against A. hydrophila under simulated intestinal juice exposure while C61 showed stable and enhanced phytase specific activity under simulated gastrointestinal conditions. C61 and T70 were incorporated into diets (PT1 and PT2) at 10⁷ CFU/g and administered in Nile tilapia juveniles for 40 days. While growth did not differ significantly among treatments, PT1 fed fish exhibited increased mucosal fold height, higher goblet cell counts in the intestine and skin. In mirror carp juveniles, both live (BSpro) and heat-inactivated (BSpara) forms of C61 were tested alongside two commercial Lactobacillus paraprobiotics (Lactob1 and Lactob2) as dietary supplements under a low feeding regime. Paraprobiotic supplementation significantly altered intestinal microbial diversity and skin goblet cell coverage. Notably, Lactob1 paraprobiotic reduced intestinal il1β expression and skin lyzc relative expression, suggesting anti-inflammatory and immunoregulatory effects at the mucosal tissues.Together, these findings highlight the probiotic potential of host-derived B. subtilis strains as both live and inactivated bacterial feed additives for Nile tilapia and mirror carp. The bacterial feed additives have demonstrated notable influence in the intestinal microbiome, mucosal health, and immunity.
Awarding Institution(s)
University of Plymouth
Award Sponsors
Department of Science and Technology-Science Education Institute
Supervisor
Daniel Merrifield, Mark Rawling
Document Type
Thesis
Publication Date
2025
Embargo Period
2025-10-22
Deposit Date
October 2025
Additional Links
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Abarra, S. (2025) Effects of Host-derived Probiotics on the Growth Performance and Health of Tilapia and Carp. Thesis. University of Plymouth. Available at: https://doi.org/10.24382/4gvr-fm75
