1. INTRODUCTION
The main challenge in the current poultry industry is how to maintain performance and health of broilers with low antibiotics utilization (Al-Garadi et al., 2025). Subtherapeutic levels of antibiotics have also been used for long period in animal feed in order to enhance their growth and minimize costs (Wang et al., 2024; Aminullah et al., 2025); nonetheless, it is currently questionable. The long-term use of antibiotics as growth promoters (AGPs) has led to antibiotics in meat and the emergence of multidrug-resistant strains, seriously endangering public health (Wang et al., 2024; Luna et al., 2025; Ahmed et al., 2024).
In response, the European Union implemented a complete ban on AGPs in 2006, followed by similar restrictive policies in other nations, such as China’s 2020 withdrawal of growth-promoting pharmaceutical additives (Luna et al., 2025). Consequently, the poultry industry is under increasing pressure to develop sustainable, antibiotic-free (ABF) production systems that use natural, safe alternatives to maintain flock health and efficiency (Luna et al., 2025; Naeem & Bourassa, 2025; Sujatha et al., 2017).
Phytogenic feed additives (PFAs), also known as botanicals or Phyto biotics, have emerged as promising alternatives to synthetic growth promoters (Oni & Oke, 2025; Hussein et al., 2024). Derived from herbs, spices, and plant extracts, PFAs contain various bioactive compounds, such as polyphenols, flavonoids, and essential oils, that exert antimicrobial, antioxidant, and anti-inflammatory effects. These natural growth promoters enhance productivity by modulating intestinal microbiota, stimulating the secretion of digestive enzymes (e.g., trypsin, amylase, and lipase), and improving gut morphology through increased villus height and surface area (Ampode & Asimpen, 2021; Islam et al., 2024; Nakamura et al., 2022; Mamun et al., 2021; Paul et al., 2020). Furthermore, PFAs improve the oxidative stability of poultry meat, meeting consumer demands for safe, high-quality organic products free from chemical residues (Oni & Oke, 2025; Fu et al., 2023; Nath et al., 2022).
In developing nations, particularly in South Asia, there are distinct social and environmental issues in broiler rearing. Feed constitutes 70–80% of the total cost, making the need for cheap and indigenous supplements a priority (Sihan et al., 2021; Ampode & Asimpen, 2021). Additionally, many South Asian countries are characterized by hot tropical climates, where ambient temperatures frequently exceed the birds' thermoneutral zone (Azzam et al., 2020). This environmental heat stress leads to increased generation of reactive oxygen species (ROS), resulting in lipid peroxidation, impaired intestinal barrier function, and a marked reduction in growth performance and survivability (Khan et al., 2012; Whitehead & Keller, 2003). In such regions, antibiotics are used more frequently because they are available over-the-counter without prescription, further fueling antimicrobial resistance (Haque et al., 2020; Sani et al., 2023). Bangladesh is one such country where the absence of antibiotics in broiler rearing is a priority but not extensively explored. Poultry is a backbone of the economy, accounting for 37% of the country’s meat production (Hamid et al., 2016). However, the industry is frequently affected by disease outbreaks and misuse of antibiotics with lack of compliance to mandatory withdrawal periods (Mamun et al., 2021). Residues of most important antibiotics such as ciprofloxacin and tetracycline in the breast meat and thigh muscles of broilers reared commercially in Bangladesh have been found to be observably high (Hussein et al., 2024; Andreu et al., 2007; Trouchon et al., 2016). Furthermore, the lack of standardized protocols for natural alternatives and the paucity of in vivo trials comparing locally available phytogenic to traditional AGPs limit the adoption of sustainable practices among Bangladeshi farmers (Khan et al., 2014).
Similarly, Thankuni is very high in its vitamin, mineral and bioactive glycosides (including asiaticoside) content which have been reported to enhance immune response, improve nutrient availability and reduce deposition of abdominal fat in chickens Aja yisafu et al. Although the effectiveness of these individual plants is established, little is known about their combined efficacy under an antibiotic free production system. The majority of previous reports have addressed single-plant extracts or used them as an extra-addition to normal diets and not as growth promoters themselves (Durrani et al., 2008). There is a critical need to investigate whether a combination of these local resources can provide synergistic effects that mimic the growth-permitting actions of antibiotics while addressing the specific challenges of tropical environments, such as heat-induced oxidative damage (Aminullah et al., 2025; Hussein et al., 2024; Islam et al., 2024; Mamun et al., 2021; Nakamura et al., 2022).
Therefore, this study aimed to evaluate the efficacy of aqueous leaf extracts of Azadirachta indica and Centella asiatica as novel growth promoters on the growth performance, feed efficiency, carcass yield, and blood parameters of antibiotic-free broiler production in Bangladesh. The novelty lies in using locally available, sustainably sourced botanical extracts to replace synthetic growth stimulants, thereby improving food safety and supporting the national economy by reducing medicinal costs.
