Humic acids are large, complex organic molecules formed through the microbial and chemical decomposition of plant and animal matter over geological timescales. Leonardite, a soft, oxidized form of lignite coal, is one of the richest natural sources of these compounds. In livestock nutrition, humic substances have a reputation for improving gut health, nutrient absorption and stress tolerance, and aquaculture researchers have increasingly wondered whether the same benefits translate to shrimp. The new study set out to answer a deceptively simple question: does supplementing feeds with leonardite humic acid, abbreviated LHA, change how juvenile shrimp use protein and lipid, and can it blunt the oxidative damage that can accumulate in intensively fed animals?

To find out, the research team designed a rigorous 3 × 3 factorial experiment. Nine experimental diets were formulated, spanning three levels of crude protein (360, 330 and 300 grams per kilogram), three levels of lipid (50, 70 and 90 grams per kilogram) and three levels of LHA supplementation (0, 9 and 12 grams per kilogram). The diets also varied systematically in digestible energy, ranging from roughly 374 to 398 kilocalories per 100 grams, creating a matrix in which the independent and combined effects of nutrient density and humic acid could be disentangled. Each diet was assigned to triplicate groups of shrimp, with 675 juveniles weighing about 5.02 grams at the start of the trial randomly distributed across the tanks.

The outcome was remarkably clear. Shrimp fed the intermediate-protein, intermediate-lipid diet supplemented with the highest dose of humic acid, a formulation labeled P33L7LHA1.2, delivered 330 grams of crude protein and 70 grams of lipid per kilogram along with 12 grams of LHA, outperformed every other group. These animals recorded the highest weight gain, the highest specific growth rate, and the best protein and lipid efficiency ratios, meaning they converted dietary protein and lipid into body tissue more effectively than their peers. At the same time, they showed the lowest feed conversion ratio, the widely used efficiency metric that every shrimp farmer watches closely, alongside the highest whole-body protein content and, notably, the lowest whole-body lipid content and hepatopancreas somatic index, a measure of the relative size of the shrimp’s central metabolic organ.

That combination, faster growth with leaner bodies and a smaller relative hepatopancreas, points to a genuinely improved metabolic state rather than simple overfeeding. In crustaceans, the hepatopancreas performs the functions of a liver and pancreas combined, secreting digestive enzymes, storing energy reserves and orchestrating lipid metabolism. When the organ enlarges, it often reflects a heavy lipid-handling burden. A lower index combined with superior growth suggests the shrimp in the LHA-supplemented groups were processing their feed with less metabolic strain, a finding with direct implications for both productivity and animal welfare in intensive systems.

The digestive enzyme data reinforced this picture. Amylase and lipase activities in the hepatopancreas rose significantly as dietary lipid levels increased, while protease activity followed the opposite trajectory, peaking in the group fed the intermediate protein-lipid ration and falling to its lowest in animals receiving the high-lipid, low-protein diet. Critically, LHA supplementation enhanced the activity of all three digestive enzymes at every dietary level, with the strongest responses observed at the 12 gram per kilogram dose. The researchers also measured two key lipid metabolic enzymes, glucose-6-phosphate dehydrogenase and carnitine palmitoyltransferase-1, both of which reached their maximum activities in the P33L7LHA1.2 group and their minimum in shrimp receiving the low-lipid diet without humic acid. Elevated activity of these enzymes indicates more efficient mobilization and oxidation of fatty acids, consistent with the leaner body composition of the best-performing animals.

Perhaps the most striking results concerned oxidative stress. Shrimp, like all aerobic animals, generate reactive oxygen species during normal metabolism, and high-lipid diets can accelerate their production, damaging cell membranes and taxing the animal’s antioxidant defenses. The trial tracked the activity of superoxide dismutase and catalase, the two frontline antioxidant enzymes, in both the hepatopancreas and the gills. As dietary lipid increased, hepatopancreatic antioxidant enzyme activities declined while branchial activities rose, revealing a tissue-specific redistribution of defensive capacity. LHA supplementation, however, reduced the activities of both enzymes across the board, with the lowest values again recorded in the group receiving the highest humic acid dose alongside the intermediate protein-lipid ration.

At first glance, lower antioxidant enzyme activity might seem undesirable, but the accompanying biochemical markers tell a different story. Shrimp fed 12 grams per kilogram of LHA displayed the lowest levels of malondialdehyde, the standard biomarker of lipid peroxidation and membrane damage, together with the lowest circulating glucose, cholesterol and triglyceride concentrations. Reduced malondialdehyde despite reduced antioxidant enzyme activity implies that the animals were experiencing less oxidative insult in the first place, requiring a less activated defense system. In other words, humic acid appears to have lightened the oxidative load itself rather than merely forcing the antioxidant machinery to work harder, a distinction that matters enormously for long-term health and stress resilience in farmed shrimp.

The metabolic blood markers add a further layer of insight. Lower plasma glucose suggests a calmer stress response, since glucose mobilization is a classic endocrine signature of physiological stress in crustaceans. Reduced cholesterol and triglyceride levels, meanwhile, align with the enhanced lipid-oxidizing enzyme activities and the lower whole-body lipid deposits, painting a coherent metabolic portrait of animals that were absorbing nutrients efficiently, burning lipid effectively and carrying less metabolic baggage. Taken together with the growth and feed efficiency data, the trial makes a strong case that humic acid is not merely a passive feed additive but an active modulator of shrimp physiology.

The practical conclusion of the study is straightforward: among the nine diets tested, the formulation containing 330 grams per kilogram of crude protein, 70 grams per kilogram of lipid and 12 grams per kilogram of leonardite humic acid produced the most favorable growth performance and antioxidant responses in juvenile P. vannamei reared in inland saline water at 10 parts per thousand. For an industry pushing into inland regions and simultaneously hunting for sustainable, non-antibiotic feed additives, the findings arrive at an opportune moment. Leonardite is an abundant, inexpensive natural resource, and if humic acid supplementation can reliably improve feed conversion, reduce fat deposition and dampen oxidative stress at a modest inclusion level, it could become a standard component of shrimp feeds in saline aquaculture systems worldwide. The researchers caution that their results apply to juveniles over a 60-day window, and further work will be needed to confirm the benefits across full production cycles, but the direction of the evidence is unmistakable. A coal-derived organic compound, of all things, may soon help shrimp thrive in water that farmers once considered worthless.

Subject of Research: Effects of dietary leonardite humic acid on growth, lipid metabolism and antioxidant status of juvenile white-leg shrimp in inland saline water

Article Title: Leonardite humic acid enhances growth, lipid utilization and antioxidant status in juvenile Penaeus vannamei

Article References: Leonardite humic acid enhances growth, lipid utilization and antioxidant status in juvenile Penaeus vannamei. (n.d.). https://doi.org/10.3389/faquc.2026.1840408

Image Credits: AI Generated

DOI: 10.3389/faquc.2026.1840408

Keywords: Penaeus vannamei, leonardite humic acid, aquaculture nutrition, inland saline water, lipid metabolism, antioxidant status, feed conversion ratio, hepatopancreas, digestive enzymes, shrimp farming, protein-lipid diets, oxidative stress

The trial involved 300 one-day-old male Cobb 500 broiler chicks, randomly assigned to five dietary treatments with four replicate pens of 15 birds each. One group received a standard corn–soybean meal control diet, while the others were fed diets supplemented with either 0.75 percent or 1.5 percent Prangos ferulacea powder, or with 750 or 1500 milligrams per kilogram of the plant’s aqueous extract. All diets were formulated to be isocaloric and isonitrogenous, meaning they delivered equivalent levels of energy and protein, so any differences between groups could be attributed to the plant material itself rather than to nutritional imbalances. The birds were monitored over a full 43-day production cycle spanning starter, grower, and finisher phases.

The plant material itself carried considerable biochemical promise. Prangos ferulacea is native to West Asia and is rich in monoterpenes, coumarins, and phenolic compounds — classes of molecules frequently associated with antioxidant, antimicrobial, and smooth-muscle-modulating activity. The researchers harvested mature aerial parts of the plant from the rangelands of Divandareh County in Kurdistan Province, shade-dried them, and milled them into powder. To prepare the aqueous extract, ten kilograms of powder were macerated in thirty liters of distilled water for twenty-four hours, filtered, and concentrated at sixty to seventy degrees Celsius, yielding roughly 10.8 percent of the starting weight as dried extract. Botanical identity was confirmed by a qualified botanist, and a voucher specimen was deposited in the university herbarium, lending the study a level of taxonomic rigor that is not always present in phytogenic feed research.

When it came to the bottom line of broiler production — body weight gain and feed conversion ratio — the results were sobering. Across the entire 43-day period, cumulative body weight gain and feed efficiency did not differ significantly among the five dietary groups. Body weights at eleven, twenty-three, and forty-three days of age were statistically indistinguishable. There was, however, a phase-specific wrinkle: during the finisher period from days twenty-four to forty-three, body weight gain was significantly reduced in the supplemented groups compared with the control, a pattern the authors suggest could relate to effects on feed intake or palatability, though the underlying cause was not directly measured. Feed intake during the grower phase was actually higher in all supplemented groups, yet this did not translate into better growth, and overall feed intake across the trial was unaffected.

Carcass characteristics told a similarly restrained story. Carcass yield and the relative weights of the heart, liver, spleen, pancreas, and bursa of Fabricius were comparable across treatments. One exception stood out: birds fed the lower dose of the powder, 0.75 percent of the diet, showed a significantly heavier gizzard relative to their body weight than both extract-fed groups and the control. The authors speculate that the fibrous, structural nature of the powdered plant material may have stimulated gizzard development, a phenomenon previously reported with coarse or fiber-rich feed components, but they caution that because particle size was not measured, this interpretation remains speculative.

Blood chemistry offered a few more points of interest. Serum triglycerides were significantly lower in birds receiving 0.75 percent powder, while very-low-density lipoprotein levels were unchanged, suggesting the plant does not exert a broad effect on lipid metabolism. Serum cholesterol was significantly lower in birds receiving both forms of supplementation compared with controls, and markers of kidney function — urea, creatinine, and uric acid — were unaffected, indicating the treatments were not harming the birds. Total protein, albumin, and globulin concentrations also remained stable, painting a picture of animals whose basic metabolic health was intact regardless of diet.

The most intriguing and, frankly, most puzzling findings emerged from the antioxidant measurements. Birds receiving the highest dose of aqueous extract, 1500 milligrams per kilogram, showed a significant increase in serum total antioxidant capacity, a measure of the blood’s non-enzymatic antioxidant potential. That might sound like a win for the plant. But the same group also exhibited significantly elevated serum malondialdehyde, a well-established marker of lipid peroxidation and oxidative damage, alongside significantly reduced glutathione peroxidase activity in the liver, one of the body’s key antioxidant enzymes. In fact, all four supplemented groups showed reduced hepatic glutathione peroxidase activity compared with controls, while liver superoxide dismutase showed only a trend toward reduction and red blood cell enzyme activities were unchanged.

This pattern — higher total antioxidant capacity coexisting with more lipid damage and less enzymatic defense — does not add up to an unequivocal antioxidant benefit, and the authors are careful to say so. Rather, they argue, it points to a complex and potentially pro-oxidant response at the highest extract dose, consistent with the dose-dependent or biphasic effects that phytochemicals sometimes display. It also underscores a broader lesson for the field: antioxidant biomarkers should be interpreted collectively rather than in isolation, and a shift in any single indicator does not necessarily signal improved health. Notably, none of the biochemical changes translated into better growth, feed efficiency, or carcass yield, reinforcing a growing consensus that modulating redox biomarkers under low-stress conditions may not produce tangible production benefits.

The study has honest limitations that shape how its findings should be read. With only four replicate pens per treatment and one bird per pen sampled for biochemical analyses, statistical power to detect subtle effects was limited. The experimental diets were formulated on calculated rather than chemically analyzed nutrient values, and the phytochemical characterization relied on spectrophotometric assays of total phenolics, flavonoids, and coumarins rather than chromatographic identification of individual compounds — meaning the differences between powder and extract cannot be tied to specific active constituents or their bioavailability. The authors also note that under the non-stressed conditions of a well-managed research facility, the birds’ endogenous antioxidant systems may already have been operating near optimal levels, leaving little room for a phytogenic additive to demonstrate measurable gains.

Where does this leave Prangos ferulacea on the crowded shelf of candidate antibiotic alternatives? The study contributes to mounting evidence that phytogenic feed additives can shift oxidative status without necessarily improving performance, particularly in animals that are not under environmental or metabolic stress. The authors chart a clear path forward: comprehensive phytochemical profiling of the plant, formal dose–response studies, investigation of molecular mechanisms such as redox-sensitive signaling pathways like Nrf2, and — perhaps most importantly — testing under oxidative-stress challenge models that better mirror the realities of commercial poultry production. Until then, the mountain herb remains a biochemical curiosity with demonstrated biological activity but, at the doses and conditions tested, no proven ticket to faster-growing, healthier chickens. For an industry under pressure to eliminate antibiotics, that distinction between biochemical activity and production benefit is exactly the kind of hard evidence that keeps the search honest.

Subject of Research: Effects of dietary Prangos ferulacea powder and aqueous extract on growth performance, carcass traits, and antioxidant status in broiler chickens

Article Title: Effects of different levels of Prangos ferulacea (L.) Lindl. (Apiaceae) powder and extract on performance, carcass characteristics, and antioxidant status in broiler chickens

Article References: Janfadah, A., Sadeghi, A. A., & Karimi, A. (2026). Effects of different levels of Prangos ferulacea (L.) Lindl. (Apiaceae) powder and extract on performance, carcass characteristics, and antioxidant status in broiler chickens. Discover Animals, 3(1), Article 98. https://doi.org/10.1007/s44338-026-00250-7

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00250-7

Keywords: Prangos ferulacea, broiler chickens, phytogenic feed additives, antioxidant status, total antioxidant capacity, malondialdehyde, glutathione peroxidase, feed conversion ratio, carcass characteristics, poultry nutrition, antibiotic alternatives, oxidative stress