Peer-reviewed publication · Aquaculture · In the living system
Trout fed a humic and fulvic top‑coating over 140 days grew heavier than controls.
Juvenile trout fed this humic and fulvic top‑coating for 140 days ended heavier and longer than controls at all three rates, with no difference among the rates; feed efficiency was not measured.
Chiasson et al., 25 September 2026. North American Journal of Aquaculture. Associated product tested.
Scope, material and route
- Studied
- Juvenile rainbow trout, 22.9 g at the start
- Design
- Four diets in triplicate tanks
- Setting
- Ontario Aquaculture Research Centre, flow-through groundwater at 8.6 °C
- Material
- A humic and fulvic acid preparation derived from oxidised leonardite, named in the paper as AC Aqua Boost, MTS Environmental Inc.; at 5 mL/kg, 0.183 g/kg humic acid and 0.153 g/kg fulvic acid in the feed
- Route
- Feed, top‑coated
- Exposure
- 5, 10 or 15 mL/kg of feed. Study exposure, not application guidance.
- Duration
- 140 days after a 14-day acclimation
Study design
Control, 0 mL/kg
Final weight 134.9 g
3 tanks
5 mL/kg
Final weight 145.7 g
3 tanks
10 mL/kg
Final weight 143.2 g
3 tanks
15 mL/kg
Final weight 142.1 g
3 tanks
Every tank started at 22.9 g a fish; weights read at day 140
- Acclimation 14 days
- Feeding trial, four diets 140 days
More study details
- Research question
- Does dietary humic and fulvic acid change growth, intestinal morphology and gut microbiome in juvenile rainbow trout?
- Experimental unit and sample size
- 12 tanks of 300 L, 60 fish per tank
- Comparator
- The same commercial diet without top‑coating
- Outcomes measured
- Weight, length, weight gain, specific growth rate, condition factor, gut pH, intestinal histology and villus length, gut microbiome
Findings
Researchers fed juvenile rainbow trout, starting at 22.9 g, a commercial diet top‑coated with a humic and fulvic acid preparation at 0, 5, 10 or 15 mL/kg, in triplicate tanks for 140 days. All three rates produced heavier fish than the control: 145.7, 143.2 and 142.1 g against 134.9 g. The rates did not differ from each other, and the authors judged 5 mL/kg most effective. Gut pH and condition factor did not change. Distal villus length was not significantly different from the control. Microbial diversity was higher at the highest rate only. Because fish were fed with a surplus, feed intake and feed conversion could not be measured.
| Difference reported | Outcome | Comparison or result | Interpretation |
|---|---|---|---|
| Final body weight | 134.9 g control; 145.7, 143.2 and 142.1 g at 5, 10 and 15 mL/kg (P < 0.001) | Heavier at all three rates; rates did not differ | |
| Final fork length | 21.0 cm control; 21.6, 21.5 and 21.3 cm (P < 0.001) | Longer fish | |
| Specific growth rate | 1.27 control; 1.32, 1.31 and 1.30 percent a day (P = 0.010) | Above control at 5 mL/kg | |
| Condition factor and gut pH | No difference | No statistically supported difference | |
| Distal villus length | Longest at 5 mL/kg and longer than at 15 mL/kg; not different from control | No supported difference against control | |
| Histology scores | Oedema and inflammation scores did not differ by rate | No rate raised these scores | |
| Microbial diversity, Shannon | Higher at 15 mL/kg than control (P = 0.034) | Composition, not measured function | |
| Microbial diversity, beta | Did not differ | No statistically supported difference |
the authors report a supported difference; they report none. Both marks are the same size.
Interpretation and limits
What this record supports
Greater weight and length in juvenile trout fed this top‑coated preparation for 140 days, without a dose response across the three rates.
What remains uncertain
- Efficiency. Feed intake and feed conversion were not measured.
- Morphology. The villus difference was not significant against the control.
- Microbiome. The shift in a Clostridium group is of unclear meaning until resolved to species, as the authors say.
Which part of the framework it informs
Environmental conditions
The physical, chemical and management context.
Microbial activity
What microbial communities do within that context.
This record informs this area.Observable function
What can be observed or measured in the host or wider system.
This record informs this area.
- a Gut wall and folds
- b Feed particle
- c Bacteria
- d Mucus layer
Source, funding and review
- Source type
- Peer-reviewed publication
- Associated products
- The tested preparation is the formulation Fulgenix Farms sells for aquaculture feed applications. The basis is the brand's own product record, which identifies the preparation named in the paper as the formulation it now sells; no independent comparison of composition is published. The study tested it under these research conditions only.
- Funding and relationships
- Co-funded by the Ontario Agri-Food Innovation Alliance and by the manufacturer of the tested preparation, which supplied it. The paper states that the manufacturer had no role in design, data collection, analysis, interpretation, manuscript preparation or the decision to submit the manuscript.
- Review status
- Prepared as an editorial summary. External scientific review has not been completed.
- What was read
- Full text read (open access).
- Original title
- Dietary humic and fulvic acid supplementation improves growth and modulates intestinal morphology and gut microbiome in Rainbow Trout
- Authors
- Chiasson M, Easton A, Snyman H, Huyben D
- Publication
- North American Journal of Aquaculture, 25 September 2026
- DOI
- 10.1093/naaqua/vrag026
- Summary prepared by
- Carbon Biome Project
- Date added
- 19 October 2026
- Cite this summary
- Carbon Biome Project. Trout fed a humic and fulvic top‑coating over 140 days grew heavier than controls. Evidence library record, added 19 October 2026. carbonbiomeproject.com/evidence/chiasson-2026-dietary-humic-fulvic-rainbow-trout-growth/
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