Ducks have strong potential as an economical source of animal protein to meet public demand for meat. In Indonesia, local duck farming also plays a strategic role in rural development by providing employment opportunities and supporting the local economy. This potential encourages duck farmers to keep improving feed efficiency while maximizing productivity. The use of antibiotic growth promoters (AGPs) is known to enhance poultry growth, but uncontrolled use in livestock farming can leave harmful residues in animal products. Because of these negative effects, AGP use has been banned in both developed and developing countries (Anggriawan et al., 2024); (Nduku et al., 2025). This ban has encouraged research on safe alternative materials (Buonaiuto et al., 2025).

Natural feed additives, such as phytobiotics, can be used as alternatives to AGPs while still supporting the production of safe animal products (El-Sabrout et al., 2026). The use of phytobiotics from local herbs has been widely explored as a sustainable option in the post-antibiotic era (Sugiharto, 2021). Centella asiatica, locally known as pegagan, is recognized as an herbal medicinal plant containing bioactive compounds with antimicrobial, antioxidant, and immunomodulatory properties that may improve growth performance and health (Nemauluma et al., 2024); (Urban et al., 2025); (Hein et al., 2025). Centella asiatica contains bioactive components, such as flavonoids, triterpenoids, centellosides, and antioxidants, that can modulate metabolic pathways, immune responses, and gut microbiota composition (Khursheed et al., 2024); (Zeng et al., 2025).

Supplementation with natural feed additives in ducks has been shown to improve performance and intestinal profiles (Iriyanti et al., 2018), as well as increase egg production and quality (Ismoyowati et al., 2022). Previous studies on C. asiatica showed positive effects on blood profiles and gut bacteria in laying hens(Ajibade et al., 2023), while 4% C. asiatica leaf meal in broiler diets improved feed utilization, carcass quality, and growth performance (Ajayi et al., 2020). (Falasifah et al., 2018) also stated that supplementation with 5% cinnamon bark flour and 10% pegagan leaf powder increased the growth rate of quail. Furthermore, (Rusli et al., 2025) have stated that C. asiatica demonstrates significant promise for utilization in poultry farming, primarily due to its capacity as an antibacterial agent.

Direct supplementation with herbal extracts often faces challenges, such as limited bioavailability and susceptibility to degradation in the upper gastrointestinal tract (Duque-Soto et al., 2024). Encapsulation is expected to protect bioactive compounds from harsh digestive conditions, improve stability and bioavailability in the gut, support controlled release, and enhance their effectiveness on gut health and growth performance (Grgić et al., 2020). Previous studies have shown that encapsulation is an innovation that can improve the bioavailability and stability of herbal additives in host animals. For example, encapsulated cinnamaldehyde improved meat quality and gut health in broilers (Yang et al., 2021); encapsulated cardamom waste extract supported digestive tract health in broilers (Alfonia et al., 2026); 0.3% encapsulated combination of dahlia extract and Bacillus subtilis improved broiler performance, while the best result based on IOFC was found at the 0.2% level (Anjani et al., 2025); and encapsulated essential oil up to 1,000 mg/kg basal diet had a positive effect on growth performance and intestinal health in ducks (Bao et al., 2023). Although the beneficial effects of the encapsulation nature extract have been documented in broilers, laying hens, and quail, information on its application in encapsulated form in ducks remains scarce, despite ducks being an economically important poultry species with distinct 80-digestive physiology. This gap underscores the novelty of evaluating encapsulated C. asiatica extract specifically in duck production. Therefore, this study aimed to investigate the use of encapsulated C. asiatica extract on growth performance, intestinal development, and intestinal microbial in Indonesian local ducks.

The addition of ECAE to the diet affected digestive organ development (Table 2), with more significant effects observed at 35 days of age than at 21 days of age. At 21 days of age, the results showed no significant differences in almost all variables, including weight, length, and organ percentage, except for jejunum length. In contrast, at 35 days of age, several parameters differed significantly among treatments. This condition may occur because, at 21 days of age, the digestive system of ducks is still immature and gut microbiota are still in a rapid growth phase. As a result, the response to ECAE treatments as phytobiotics may remain limited. The effect on growth and intestinal morphology becomes more evident in the finisher phase (22 to 42 days) than in the starter phase (1 to 21 days), which may explain why the response to feed additives was not significant during the earlier stage (Abdelli et al., 2021). This finding aligns with (Obianwuna et al., 2024), who stated that livestock responses to treatments depend on the duration and dosage of administration.

Supplementation with encapsulated C. asiatica extract influenced gut development in 35-day-old ducks. Encapsulated C. asiatica extract (ECAE) supports the growth and regeneration of intestinal epithelial cells through the modulation of gut microbiota. This modulation increases the production of short-chain fatty acids (SCFAs) (Ge et al., 2023). The mechanism begins with the antibacterial properties of triterpenoid compounds in C. asiatica. According to (Ramli et al., 2020), triterpenoid compounds can inhibit microbial growth by damaging microbial cell membranes and cell walls. These compounds selectively inhibit the growth of pathogens such as coliform, without disrupting beneficial bacteria. As a result, beneficial bacteria, such as lactic acid bacteria, can proliferate more effectively. The dominant lactic acid bacteria then ferment undigested feed and ECAE components, producing SCFAs, including acetate, butyrate, and propionate. Although SCFA levels were not measured in this study, butyrate is well known as an energy source for mitochondria in intestinal epithelial cells, promotes cell proliferation, and improves gut barrier function (Liu et al., 2021). In addition, (Zhang et al., 2019) stated that stem cells in the intestinal crypt proliferate and differentiate into functional epithelial cells to replace old or damaged cells, resulting in higher and wider villus structures.

An interesting finding at 35 days was that duodenum weight, length, and percentage, as well as caecum weight, showed significant effects in the control treatment (T0). This condition suggests that smaller digestive organs can still function optimally in nutrient absorption, as supported by the body weight gain data in Table 5, where ECAE treatment produced a significant increase. Furthermore, digestive organ length and weight in this study are presented in relative terms, where the calculations are influenced by live weight. Consequently, higher body weight may lead to lower relative values for organ weight and length. This explains why the control treatment had lower body weight, while the relative weight and length of the digestive organs were higher. (Wang et al., 2016) reported that broilers with lower body weight gain in the control group had higher relative intestinal weight than broilers with higher body weight gain in the treatment group. Differences in intestinal length values that were significant in absolute terms may become non-significant when presented as relative values or as a percentage of the organ relative to total live weight (Gorenz et al., 2024).

The effect of encapsulated C. asiatica extract on gastrointestinal organ development may result from the main mechanisms of its bioactive compounds, such as flavonoids, centellosides, antioxidants, and triterpenoids (Sabaragamuwa et al., 2018). These compounds can modulate metabolic pathways and gut microbiota, thereby supporting more efficient organ development. The encapsulation used in this study enhanced the stability and bioavailability of these compounds in the digestive tract. This finding aligns with (Natsir et al., 2019), who showed that feed additives administered in encapsulated form produced better results than those given in non-encapsulated form. It is also supported by (Ardiansah et al., 2020), who found that supplementation in encapsulated form resulted in better relative carcass performance, along with higher and wider villi, compared to the powdered form.

Supplementation with ECAE in feed significantly increased the population of gut lactic acid bacteria (LAB) in ducks. Table 3 shows that administration at the 0.4% (T2) and 0.6% (T3) levels resulted in higher LAB populations than the other treatments. The addition of ECAE can support LAB growth. Several references have reported antibacterial and antioxidant activities from the bioactive compounds in C. asiatica, which can modulate the composition of the gut microbiota (Rusli et al., 2025); (Khursheed et al., 2024); (Zeng et al., 2025). These compounds work by selectively inhibiting the growth of pathogenic bacteria while promoting the proliferation of beneficial microbes, thereby restoring microbiota homeostasis and preventing dysbiosis. Supplementation with prebiotics, probiotics, or other phytogenic feed additives can modify microbial balance and encourage eubiosis (Salahi et al., 2025). This observation is supported by previous research on the use of probiotics and organic acids, which were shown to suppress Campylobacter proliferation in broiler chickens (Mortada et al., 2020).

The statistical results for T0 and T1 showed no significant difference, whereas T2 and T3 showed significant effects. This outcome may be related to the treatment levels. At the low dose of 0.2%, the microbiota was not significantly modulated because the concentration of bioactive compounds in C. asiatica may not have reached the required threshold. Meanwhile, at the 0.4% and 0.6% levels, the bioactive compound content was sufficiently high to produce selective antimicrobial effects by suppressing pathogens while stimulating the growth of lactic acid bacteria. Triterpenoids and flavonoids can disrupt the cell membranes of pathogenic bacteria, thereby inhibiting their growth, while lactic acid bacteria continue to thrive. Bioactive compounds, such as flavonoids, alkaloids, phenols, saponins, and tannins in plants, can act as antibacterial agents against pathogens (Abdelli et al., 2021). This condition supports the continuous production of short-chain fatty acids (Fusco et al., 2023), creating an acidic environment that is favorable for LAB.

The addition of ECAE significantly altered the morphology of the small intestine. Supplementation at 0.6% resulted in higher villi in the jejunum and ileum compared to the 0.2% and 0.4% levels. The villus-to-crypt (V/C) ratio also increased significantly in the jejunum and ileum at the 0.6% supplementation level. These results indicate an increase in the absorption surface area, along with faster epithelial regeneration (Nguyen et al., 2021). These improvements were likely supported by the antimicrobial, antioxidant, and immunomodulatory mechanisms of C. asiatica, which can reduce oxidative stress and inflammation in the intestinal mucosa (Nemauluma et al., 2024);(Urban et al., 2025). Flavonoids in C. asiatica can stimulate mucus secretion, leading to better villus protection and enhanced growth of beneficial bacteria (Prihambodo et al., 2020). (Rusli et al., 2025) reported that flavonoids in C. asiatica leaves have proven antibacterial and antioxidant properties, which significantly improve small intestine health and function, particularly in the nutrient absorption process. The beneficial effects of this improvement include increased villus height and crypt depth. The elongation of villi and deepening of intestinal crypts accelerate epithelial cell turnover and enhance the intestinal absorption capacity.

Encapsulated C. asiatica is highly effective in improving villus morphology, even at low doses. The application of encapsulation to plant bioactive substances, such as essential oils or extracts, protects these substances from external factors and degradation, thereby supporting the long-term stability of the active ingredients(Zabot et al., 2022). This view is consistent with (Ma’rifah et al., 2025), who reported that the addition of encapsulated starfruit extract to broiler chicken rations improved intestinal morphology, as shown by increased villus height and deeper small intestinal crypts.

Improvements in gut development, microbial balance, and intestinal morphology led to a significant increase in growth performance. Table 5 shows the best results at the 0.2% ECAE administration level, where final body weight and body weight gain increased while FCR decreased. These results indicate that the lowest ECAE level improved feed nutrient utilization through more efficient digestive organs, healthier microbiota, and a larger intestinal absorption surface area. This is supported by (Ajayi et al., 2020), who reported an increase in daily and final body weight, along with a decrease in FCR, after the addition of C. asiatica leaf extract. Similarly, (Ajibade et al., 2023) reported improvements in health and productivity in chickens supplemented with C. asiatica.

The growth performance parameters show that T2, overall, was able to improve growth and feed efficiency without affecting feed intake or carcass yield. This can be seen from the increase in body weight gain and final body weight, while the feed conversion ratio (FCR) decreased, indicating greater efficiency. These findings suggest that the addition of encapsulated C. asiatica extract (ECAE) supports better nutrient utilization while maintaining good growth performance in ducks. The findings are consistent with previous research showing that phytobiotic supplementation can increase final body weight and feed efficiency in Alabio meat ducks as an alternative to antibiotics (Biyatmoko et al., 2021). Overall, these results suggest that C. asiatica can be used as a natural growth promoter-based additive. (Ogunka-Nnoka et al., 2020) stated that C. asiatica contains various bioactive compounds, such as flavonoids, phenolics, polyphenols, alkaloids, and phytic acid. These components can serve as natural feed additives for poultry.

The addition of encapsulated C. asiatica extract showed progressive improvements according to the treatment levels. Thus, supplementation with C. asiatica extract promotes more productive development from the duodenum to the jejunum and ileum, resulting in an intestine with better nutrient absorption capacity than the control treatment. This condition ultimately leads to better growth performance and feed efficiency.

Supplementation with encapsulated Centella asiatica extract at all levels (0.2%, 0.4%, and 0.6%) positively affected digestive organ development, intestinal morphology, gut microbial balance, and growth performance, with 0.6% encapsulated C. asiatica extract as the best supplementation level.

The authors declare no conflict of interest related to personal relationships, financial interests, or other organizations or individuals connected to the material used and discussed in this manuscript.

The authors gratefully acknowledge the support of the Institute for Research and Community Service (LPPM Undip) in the International Publication Research contract number: 222-462/UN7.D2/IV/2025.

The authors state that generative AI tools were used solely to improve readability and language clarity under human oversight. The authors retain full responsibility for the scientific content, data analysis, and interpretation.