Eucommia Ulmoides in Aquaculture Boosts Croaker Growth
A four-week feeding trial on large yellow croaker, China’s top farmed marine fish, shows that Eucommia ulmoides in aquaculture feed at 0.3 percent lifted weight gain nearly twofold and halved the feed conversion ratio. Integrated transcriptomic and lipidomic data point to remodeled lipid pathways rather than a simple growth bump.
Quick answer
Eucommia ulmoides in aquaculture feed changed the growth and metabolism of large yellow croaker in four weeks. At 0.3 percent of diet, weight gain rose from 56.05 to 109.34 grams and the feed conversion ratio dropped from 2.68 to 1.38. Plasma triglycerides and a lipid-peroxidation marker fell while antioxidant markers rose. Multi-omics flagged glycerolipid and glycerophospholipid metabolism as the pathways most affected.
Why Eucommia ulmoides in aquaculture is worth a closer look
Large yellow croaker, Larimichthys crocea, is one of the most important marine aquaculture species in China and ranks first in production among farmed marine fish. Like many farmed fish, it is prone to fatty liver and disordered lipid metabolism under intensive feeding, which hurts growth, fillet quality, and health. Plant-derived feed additives that tune lipid metabolism without antibiotics fit the direction aquaculture is already moving.
Eucommia ulmoides, known as Du Zhong bark, is a traditional plant used in livestock and fish feeds for its bioactive compounds. Earlier work in grass carp, channel catfish, and other fish linked it to better growth, lipid balance, and antioxidant status. What was missing was a mechanistic read: not just whether it helped, but which genes and lipid molecules moved, and whether the two omics layers agreed.
How the feeding trial was built
The trial compared a control diet with one where 0.3 percent high-gluten flour was replaced by 0.3 percent Eucommia ulmoides bark powder. Fish were fed twice daily at 3 percent of body weight for four weeks.
| Element | Detail |
|---|---|
| Species | Large yellow croaker, Larimichthys crocea |
| Groups | CON (basal diet), EU (basal diet plus 0.3 percent Eucommia ulmoides) |
| Duration | 4 weeks |
| Feeding | Twice daily at 3 percent of body weight |
| Diet swap | 0.3 percent high-gluten flour replaced by 0.3 percent E. ulmoides |
| Basal diet | 48.83 percent crude protein, 12.23 percent crude lipid, 11.03 percent ash, 8.08 percent moisture |
| Sampling | 4 biological replicates for plasma, 5 for lipidomics |
| Statistics | One-way ANOVA; P less than 0.05, P less than 0.01, P less than 0.001 |
Survival stayed above 99.3 percent, with fewer than five fish lost per cage across groups. The basal diet composition was verified from the same manufacturer’s reported proximate values, so the only intentional difference between groups was the bark substitution.
What the growth and body indices showed
The EU group outperformed the control on every growth measure. Final weight rose from 233.75 to 288.34 grams, weight gain from 56.05 to 109.34 grams, and specific growth rate from 0.98 to 1.71 percent per day. All differences were significant at P less than 0.05.
| Index | CON | EU | Read |
|---|---|---|---|
| Final weight (g) | 233.75 plus or minus 16.40 | 288.34 plus or minus 13.96 | Higher |
| Weight gain (g) | 56.05 plus or minus 3.02 | 109.34 plus or minus 19.76 | Nearly doubled |
| Specific growth rate (%/day) | 0.98 plus or minus 0.05 | 1.71 plus or minus 0.19 | Higher |
| Feed conversion ratio | 2.68 plus or minus 0.25 | 1.38 plus or minus 0.20 | Halved, better |
| Condition factor (%) | 1.67 plus or minus 0.08 | 1.46 plus or minus 0.15 | Lower |
| Hepatosomatic index (%) | 2.17 plus or minus 0.52 | 1.66 plus or minus 0.31 | Lower, less liver lipid |
The feed conversion ratio fell from 2.68 to 1.38, meaning far less feed per unit of gain. The hepatosomatic index dropped from 2.17 to 1.66 percent, a signal of less hepatic lipid accumulation, and the condition factor eased from 1.67 to 1.46 percent. Together these point to better feed use and a leaner liver, not just faster weight.
The plasma biochemistry told the same story
Blood markers lined up with the growth picture. Plasma triglyceride and malondialdehyde, a lipid-peroxidation marker of oxidative stress, were significantly lower in the EU group at P less than 0.001 and P less than 0.01 respectively. Superoxide dismutase activity and glutathione content, two antioxidant markers, were significantly higher at P less than 0.05.
| Plasma marker | Direction in EU group | Significance |
|---|---|---|
| Triglyceride | Lower | P less than 0.001 |
| Malondialdehyde | Lower | P less than 0.01 |
| Superoxide dismutase | Higher | P less than 0.05 |
| Glutathione | Higher | P less than 0.05 |
Lower triglycerides and oxidative damage alongside higher antioxidant defense is the biochemical signature of improved lipid handling and less stress. It matches the lower hepatosomatic index and supports the idea that the bark acts on metabolism, not merely appetite.
What the multi-omics revealed
The study did not stop at growth and blood. It ran transcriptomics and lipidomics on the same fish and merged the two. The convergence was specific: glycerolipid metabolism and glycerophospholipid metabolism were the principal pathways represented in both datasets. Genes mapped to glycerolipid metabolism tracked reactions making neutral lipids, while genes mapped to glycerophospholipid metabolism tracked phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, and their precursors.
| Layer | Principal finding |
|---|---|
| Transcriptome | Clear separation between groups; pathways enriched for lipid metabolism |
| Lipidome | Distinct lipid profiles; differential lipid molecules selected at log2 fold change 2 or more, P less than 0.01, VIP above 1.5 |
| Integrated | Glycerolipid and glycerophospholipid metabolism shared by both omics |
| ABC transporter | Upregulated abca3, abcd2, abcd4; downregulated sec61g, sec11a, spcs3, hsp90b1, pdia4, calr3b |
The ABC transporter pathway also shifted, with abca3, abcd2, and abcd4 up and several protein-export and endoplasmic-reticulum genes down. That pattern fits a cell actively moving lipids and managing protein load. The key point is agreement: two independent omics layers named the same lipid pathways, which is stronger evidence than either alone.
The counterintuitive part: growth and lipid remodeling moved together
The simple story would be that the bark made fish eat better or grow faster through unknown means. The data say something tighter. Improved growth arrived together with a remodeled lipid profile, lower liver lipid, and higher antioxidants. The integrated analysis places the lipid pathways at the center, suggesting the growth gain is at least partly a metabolic effect, not just more feed converted.
That matters because it reframes the additive from a vague tonic to a metabolic lever. For formulators, the question becomes which lipid pathway nodes to target and verify, rather than whether the fish got bigger.
What this means for aquaculture feed formulators
Three steps follow from the work.
- Test Eucommia ulmoides bark at around 0.3 percent of diet in marine finish fish where fatty liver and lipid disorder limit performance, since the croaker trial showed clear gain and feed-efficiency benefits.
- Track plasma triglyceride, malondialdehyde, superoxide dismutase, and glutathione alongside weight, because the metabolic and antioxidant signals move with growth and flag liver stress early.
- Pair growth trials with transcriptomic or lipidomic checks when possible, since the two omics layers agreeing on lipid pathways is what turns a feeding result into a mechanism worth building on.
Limitations to keep in view
The work is a four-week trial on one species and one life stage, so dose response and longer-term effects are open. Lipidomics used no external internal standard, so abundances are relative, not absolute, and the principal pathways are a strong association rather than proven cause. The authors state the multi-omics result is hypothesis-generating and call for enzymatic validation of specific genes and for gut microbiota and barrier measurements to test whether intestinal responses contribute. Direct proof that lipid remodeling caused the growth gain still needs targeted studies.
Bottom line
Eucommia ulmoides in aquaculture feed at 0.3 percent nearly doubled weight gain and halved the feed conversion ratio in large yellow croaker over four weeks, with lower liver lipid and better antioxidant status. Integrated transcriptomics and lipidomics converged on glycerolipid and glycerophospholipid metabolism as the pathways most affected. The evidence supports the bark as a metabolic feed lever worth validating further in marine finish fish.
FAQ
What did 0.3 percent Eucommia ulmoides do for the fish?
At 0.3 percent of diet, weight gain rose from 56.05 to 109.34 grams and the feed conversion ratio fell from 2.68 to 1.38 over four weeks. Specific growth rate went from 0.98 to 1.71 percent per day. Hepatosomatic index dropped from 2.17 to 1.66 percent, signaling less liver lipid accumulation alongside the faster, leaner growth.
Is Eucommia ulmoides an antibiotic replacement?
It is a plant-derived feed additive, not an antibiotic, and the study reports no antimicrobial claim. Its value here was metabolic: better lipid handling, lower oxidative stress, and improved feed efficiency. It fits the broader shift in aquaculture toward functional feeds that reduce reliance on pharmaceuticals rather than replace a specific drug.
Which lipid pathways changed the most?
Integrated transcriptomics and lipidomics converged on glycerolipid metabolism and glycerophospholipid metabolism as the principal shared pathways. Genes linked to neutral lipid synthesis and to phosphatidylglycerol, phosphatidylcholine, and phosphatidylethanolamine precursors moved together. The agreement of two omics layers is the strongest signal in the dataset.
Did the fish stay healthy on the additive?
Survival stayed above 99.3 percent, with fewer than five fish lost per cage, so the additive caused no obvious mortality. Plasma triglycerides and malondialdehyde fell while superoxide dismutase and glutathione rose, markers of better lipid balance and antioxidant defense. The four-week trial showed no adverse signal in the measured endpoints.
How were the fish fed in the trial?
Fish ate a basal diet or that diet with 0.3 percent high-gluten flour swapped for 0.3 percent Eucommia ulmoides bark, fed twice daily at 3 percent of body weight for four weeks. The basal diet was 48.83 percent crude protein and 12.23 percent crude lipid. The only intentional difference between groups was the bark substitution.
Why use two omics methods together?
Transcriptomics shows gene and pathway responses, while lipidomics shows actual lipid molecules, and the two complement each other. Here both named the same lipid pathways, which strengthens the conclusion beyond either alone. Single-layer reads can mislead, so the merged view is what makes the lipid finding credible.
Does this prove the bark caused the growth gain?
No. The multi-omics result is hypothesis-generating, and lipid abundances were relative, not absolute. The authors call for enzymatic validation of specific genes and for gut and barrier measurements to test causation. The growth and lipid improvements are real and associated, but direct proof that pathway remodeling drove the gain still needs targeted studies.
Can other fish benefit from this additive?
Earlier studies in grass carp, channel catfish, and spotted sea bass linked Eucommia ulmoides to better lipid metabolism and antioxidant status, so the effect may extend beyond croaker. This trial, however, tested only large yellow croaker at one life stage for four weeks. Other species, doses, and durations should be confirmed before broad use.
What blood markers should a farm track?
Plasma triglyceride and malondialdehyde fell while superoxide dismutase and glutathione rose in the EU group, so those four are the practical panel. Triglyceride and malondialdehyde flag liver lipid and oxidative stress, and the antioxidants flag defense capacity. Watching them with weight catches metabolic trouble before it shows in growth.
Is large yellow croaker an important species?
Yes. Larimichthys crocea is among the most important marine aquaculture species in China and ranks first in production among farmed marine fish. Its tendency to fatty liver under intensive feeding makes lipid-metabolism additives directly relevant to producers, which is why a clean metabolic lever matters for the sector.
How long was the Eucommia ulmoides trial?
The feeding trial lasted four weeks, with fish sampled at the end for growth, plasma biochemistry, transcriptomics, and lipidomics. Survival and growth were tracked across the period, and the basal diet composition was verified from the manufacturer. Four weeks was enough to show clear growth, feed-efficiency, and metabolic differences.
