The use of antibiotics as growth promoters (AGPs) within the poultry industry has been banned in numerous countries due to residue and resistance issues. In Indonesia, this has been effective since January 1, 2018, with the issuance ofthe Regulation of the Ministry of Agriculture of the Republic of IndonesiaNo. 14 of 2017. Thereafter, antibiotics are used solely for the treatment and prevention of diseases under the supervision of a veterinarian. This ban on AGPs presentsserious challenges to broiler chicken farmers in maintaining the growth and health of their chickens.
       
Previous studies have shown that plant extracts can be used as a substitute for AGP due to their bioactive compounds that can function as antioxidants. Clove (Syzygium aromaticum), for example, contains phenolic compounds such as phenols and flavonoids, making it a potential source of natural antioxidants (El-Maati et al., 2016; Cheikhyoussef et al., 2022; Sapsuha et al., 2023). This plant grows abundantly in various regions in Indonesia, Malaysia and other Southeast Asian countries (Idowu et al., 2021; Cortés-Rojas et al., 2014). Traditionally, it has been widely used as a medicinal plant. Similarly, clove leaves also contain phenolic compounds,including flavonoids, quercetin, chlorogenic acid and caffeic acid (Cheikhyoussef et al., 2022; Ullah et al., 2023).
       
However, phenolic compounds contained in plant extracts naturally have low stability because they are susceptible to temperature changes during storage (Ali et al., 2018). Oxidative degradation of phenolic compounds can reduce the antioxidant activity of these materials (Nagarajan et al., 2020). Therefore, efforts are needed to prevent oxidation of phenolic compounds, one of which is through encapsulation (Adefegha et al., 2022), the process of coating a material with the aim of increasing its shelf life by preventing degradation reactions of bioactive components. Encapsulation can also mask taste or odor and minimize mold growth (Baysan et al., 2021). Encapsulation techniques using freeze-drying methods and maltodextrin as coating materials are generally recommended for materials containing bioactive components that are unstable at high temperatures, such as phenolic compounds (Sturm et al., 2019).
       
This study aims to examine the effects of encapsulated clove leaf extract on the performance of broiler chickens, which has not been explored in previous studies.

Clove leaf extract encapsulation process
 
Mature clove leaves (yellowish to dark brown) were weighed, washed thoroughly, drained and dried indoors, away from direct sunlight. Then, the dried clove leaves were ground to produce a fine powder.
       
Powdered clove leaves were extracted using a maceration technique with a ratio of 1:4 between the simplicia and the solvent. For this process, the clove leaf simplicia was soaked in 70% ethanol for 72 hours at room temperature. The soaked simplicia was filtered using filter paper to obtain a liquid extract or filtrate. Then, the filtrate was concentrated using a vacuum rotary evaporator at a maximum temperature of 60°C until a paste-like clove leaf extract was obtained (Sjafani et al., 2022).
       
The clove leaf extract was encapsulated using maltodextrin as the coating material. Maltodextrin was dissolved in distilled water with a ratio of maltodextrin to distilled water of 1:3. Then, the dissolved maltodextrin was mixed with the clove leaf filtrate with a ratio of filtrate to maltodextrin of 1:5. After the filtrate was completely dissolved in the liquid maltodextrin, a freeze-drying process was carried out to obtain the encapsulated clove leaf extract (Tamara, 2024).
 
In vivo experiment
 
This study has been approved by the Research Ethics Committee of the Faculty of Medicine and Health Sciences, Universitas Khairun (No. 058/UN44/C.9/KEP/2025). A total of 250 unsexed Lohmann broiler chickens were raised together from 0 to 7 days of age with commercial feed. On the 8^th day, they (body weight 157.21±3.24 g) were randomly assigned to five treatment groups, namely CONT (basal feed without encapsulated clove leaf extract), EC0.5 (basal feed + encapsulated clove leaf extract of 0.5 g/kg feed), EC1.0 (basal feed + encapsulated clove leaf extract of 1.0 g/kg feed). EC1.5 (basal feed + encapsulated clove leaf extract of 1.5 g/kg feed) and EC2.0 (basal feed + encapsulated clove leaf extract of 2.0 g/kg feed). Each treatment was replicated five times.
       
Throughout the growth phase, the chickens were housed in well-ventilated broiler enclosures with sawdust used for bedding. They received a specially designed mash feed intended for starter (days 8-21) and finisher (days 22-35), detailed in Table 1. Both feed and water were made available freely until the 35^th day. On day 4, all chickens were administered a commercial Newcastle  disease (ND) vaccine using eye drops, followed by drinking water on day 18 and were also given the Gomboro vaccine in their drinking water on day 12.


       
Weekly updates were made on weight increase, feed intake and feed conversion rate (FCR). To minimize physiological variations linked to gender and body weight, male chicks that matched the body weight of each cage were chosen for sampling. On day 35, blood samples were taken via the brachial vein in the wing of male chicks from each replication (five chicks per treatment). The collected blood samples were placed in tubes containing ethylenediaminetetraacetic acid (EDTA) to obtain a complete blood profile. For pragmatic purposes, the chickens that had earlier provided blood samples were processed for meat and their insides were extracted. The internal organs of the trial chickens were gathered and weighed using a precise scale.
       
This research utilized a completely randomized design approach. The collected data were evaluated through ANOVA using SPSS version 16.0. In addition, Duncan’s multiple range test was applied to identify statistically significant differences among the means (p<0.05).

Broiler chicken performance
 
As shown in Table 2, groups EC1.0, EC1.5 and EC2.0 experienced greater body weight gain (p<0.05) during the rearing period, compared to CONT and EC0,5. Nevertheless, there was no notable difference detected between EC1.5 and EC2.0 (p>0.05). The use of encapsulated clove leaf extract in different proportions led to a marked increase in feed intake and a reduced conversion rate (p<0.05), in comparison to the CONT.


       
The results of this study indicate that feeding broiler chickens with encapsulated clove leaf extract can improve their growth performance. To date, no studies in the literature have described the effects of encapsulated clove leaf extract on increasing body weight gain in broiler chickens. The effectiveness of encapsulated clove leaf extract is likely attributed to the synergistic action of various phytochemicals present in clove leaves (El-Maati et al., 2016; Idowu et al., 2021; Sapsuha et al., 2023). This can result in improved physiological condition of the chickens. Encapsulation serves as a delivery system that maintains the stability of clove leaf bioactive compounds until they reach the intestine. If released slowly, flavonoids contained in herbal plants help inhibit the growth of pathogenic bacteria (E. coli and Salmonella) and support the balance of intestinal microflora (Dwivedi et al., 2023). In addition, the use of encapsulated clove leaf extract can increase feed consumption and weight gain in broiler chickens. This is because encapsulation lessens the pungent aroma of herbal extracts, making it more pleasant for chickens to eat (Sugiharto and Ayasan, 2023). Improved feed conversion demonstrates better feed utilization and efficiency.
       
The findings of this study confirm those of prior studies, which reported that phytochemicals such as flavonoids, phenols and saponins in plants used as phytogenics increase growth rates and feed efficiency in broiler chickens due to their ability to maintain the integrity of the intestinal mucosa and enhance intestinal digestibility (Citra et al., 2025; Rajab et al., 2025). Likewise, additional research has indicated that clove foliage displays antibacterial characteristics (El-Maati et al., 2016; El-Refai et al., 2020) that can promote the proliferation of helpful bacteria, neutralize harmful bacteria and assist in the metabolism and uptake of nutrients within the digestive system, thereby enhancing the growth performance of broiler poultry (Tahir et al., 2019).
 
Relative weight of internal organs in broiler chickens
 
The results revealed that feeding broiler chickens with encapsulated clove leaf extract had no effect (p>0.05) on the weight of their internal organs (Table 3). Previous studies have shown that the administration of plant extracts can affect the internal organs of broiler chickens, particularly the liver. This is because direct exposure to high concentrations of bioactive compounds contained in plant extracts creates a metabolic burden (Nufer and Shatskikh, 2021; Sapsuha et al., 2021). In contrast, the results of this present study reveal that administering encapsulated clove leaf extract does not affect the relative weight of the internal organs of broiler chickens, as the active compounds are released slowly (controlled release) with encapsulation, thus reducing the workload of the liver (Yun et al., 2021).


 
Broiler chicken blood profile
 
As presented in Table 4, feeding broiler chickens with encapsulated clove leaf extract did not affect (p>0.05) their blood profile.


       
Normal blood profiles in broiler chickens are maintained by their body homeostasis. This study shows that administering encapsulated clove leaf extract neither stimulates nor suppresses hematopoiesis in broiler chickens, as evidenced by the absence of an increase in their blood profile, particularly their leukocytes, erythrocytes and hemoglobin. While the exact cause of this condition remains unknown, this is possibly because clove leaf’s bioactive properties work in the digestive tract. This finding supports a previous study, which reported no effect of administering plant extracts to broiler chickens on their blood profiles (Gharechopogh et al., 2021).

Administering encapsulated clove leaf extract at a dose of up to 1.5 g/kg feed can improve the performance of broiler chickens without negatively affecting their blood profile.

This study was supported by the Ministry of Higher Education, Science and Technology of the Republic of Indonesia through the 2025 Master’s Thesis Research (PenelitianTesisMagister /PTM) Scheme with contract No. 074/C3/DT.05.00/PL/2025; 481/UN44/LI/PG.12/2025.
 
Disclaimers
 
The opinions and findings presented in this article are exclusively those of the authors and might not reflect the perspectives of the organizations they are associated with. The authors hold responsibility for the precision and thoroughness of the information shared, yet they do not assume any responsibility for any consequences, whether direct or indirect, that may arise from using this material.
 
Informed consent
 
All procedures involving animals for experimentation received approval from the Committee responsible for the care and management of experimental animals and the Research Ethics Committee of the Faculty of Medicine and Health Sciences at Universitas Khairun approved the handling methods (No. 058/UN44/C.9/KEP/2025).

The writers state that there are no interests that conflict with the release of this article. No financial support or sponsorship impacted the study’s design, data gathering, analysis, choice to publish, or the drafting of the manuscript.