The global push for antibiotics free poultry production has intensified the search for natural growth promoters. This study evaluated the effects of graded levels of Caesalpinia bonduc leaf oil on the growth performance and nutrient digestibility of broiler chickens. A total of 300 -1 day old broiler chicks were randomly assigned into five dietary treatments in a Completely Randomized Design for a 42 day trial. The birds were reared in a battery cage and fed basal diet formulated to NRC (1994) standards. The treatment consisted of: Treatment 1 (T1) basal diet only; T2 (basal diet with 0.5 mL Caesalpinia bonduc leaf oil/kg diet; T3 (basal diet with 1.0 mL Caesalpinia bonduc leaf oil/kg diet; T4 (basal diet with 1.5 mL Caesalpinia bonduc leaf oil/kg diet and T5 (basal diet with 2.0 mL Caesalpinia bonduc leaf oil/kg diet. Phytochemical analysis of T2 (basal diet with 0.5 mL Caesalpinia bonduc leaf showed that it contained phenols (13.76 %), flavonoids (10.22 %), terpenoids (8.77 %), tannins (4.31 %), and saponins (1.87 %). Result showed that the overall body weight gain was significantly higher (p<0.05) in birds receiving Caesalpinia bonduc leaf oil (T2-T5) compared to the control group (T1). Correspondingly, the feed to gain ratio significantly improved (p<0.05) in oil supplemented groups. Nutrient digestibility of dry matter, organic matter, crude protein, ether extract and ash was significantly enhanced (p<0.05) in birds fed Caesalpinia bonduc leaf oil diet. It was concluded that Caesalpinia bonduc leaf oil at an inclusion of 2.0 mL/kg is an effective phytogenic feed additive for optimizing growth and nutrient utilization in broiler chickens.

The global poultry industry is currently undergoing a significant transition toward sustainable, antibiotic-free production systems (Abdelli et al., 2021; El-Sayed et al., 2022). Traditionally, antibiotic growth promoters were used extensively to enhance performance and control subclinical infections; however, their use has been largely restricted or banned in many countries due to the rising threat of antimicrobial resistance and the presence of drug residues in animal products (Alagbe, 2024; Adewale et al., 2021). This shift has catalyzed research into phytogenic feed additives, basically derived from plants, such as herbs, spices, and essential oils—as effective natural alternatives (Haque et al., 2020; Ojediran et al., 2024). Among these natural alternatives, Caesalpinia bonduc (L.) Roxb., commonly known as the "grey nicker nut," stands out due to its rich profile of secondary metabolites, including tannins, flavonoids, alkaloids, and terpenoids (Paraskeuas et al., 2017; Ri et al., 2017). Essential oils extracted from it's  leaves are particularly valued for their lipophilic nature and broad-spectrum antimicrobial activity (Singh et al., 2022; Mohiti et al., 2017). These oils have the potential to modulate the intestinal microbiota, stimulate the secretion of endogenous digestive enzymes, and improve the morphology of the gastrointestinal tract, thereby enhancing both growth performance and nutrient utilization in broiler chickens (Engberg et al., 2012; Giannen et al., 2018). Despite the well-documented potential of various phytogenics, the poultry industry faces persistent challenges in maintaining high productivity and bird health in the absence of conventional antibiotics (Bozkurt et al., 2012; Bravo et al., 2011). Standard diets often fail to provide the necessary gut health support needed to maximize feed efficiency and nutrient digestibility, leading to increased susceptibility to enteric pathogens and economic losses (Alp et al., 2012; Amerah et al., 2011; Hernandez and Alagbe, 2024b). Furthermore, while Caesalpinia bonduc is known for its pharmacological properties, there is a significant lack of standardized data regarding its application as a leaf essential oil in broiler nutrition. The efficacy of phytogenic feed additives can be highly inconsistent due to variations in inclusion levels, plant part used, and the specific chemical composition of the oil (Isabel et al., 2009; Xu et al., 2003). Without a comprehensive evaluation of its specific effects on growth parameters and nutrient digestibility, its potential as a reliable feed additive remains largely untapped and unoptimized for commercial use. This study is justified by the urgent need for safe, residue-free, and cost-effective growth promoters that align with modern consumer demands for safe products from birds (Hamedi et al., 2017; Park et al., 2018). Caesalpinia bonduc is an abundant, locally available medicinal plant that offers a sustainable alternative to synthetic chemicals (Jumroz et al., 2006; Chen et al., 2020).

Experimental site and duration

The experiment was conducted over a 42 days period at the Poultry Section, Gandhi College of Agricultural Technology, Rajasthan, India between the months of June – September 2025. All experimental procedures followed the guidelines for the care and use of experimental birds outlined at the Animal Production and Health Department of the Institution (ASD/008L/2025).  Preparation of plant materials, Identification and extraction of oil Fresh Caesalpinia bonduc leaves were harvested in the early morning within the Biological Sciences Department garden, Gandhi College of Agriculture, Rajasthan India and taken to Botany Department of the same institution for proper authentication by Mr. Ham Singh and assigned a reference number GD/09/2411 for future botanical verification. The collected leaves were manually sorted, washed with distilled and spread on a plastic tray to dry under shade for 12 days until a constant weight was achieved. The dried leaves was pulverized into coarse powder with mortar and pestle to increase the surface area for extraction and stored in an airtight containers until further use. 100 g of pulverized Caesalpinia bonduc leaf was taken to the laboratory to determine the composition of phytochemicals in the sample. Analysis (Table 2) was carried out according to the methods outlined by Harbone (1998).  Extraction of Caesalpinia bonduc leaf oil was carried out using Clavenger –type equipment. 200 g of pulverized Caesalpinia bonduc leaves was placed in a 2 liter round bottom flask mixed with distilled water at a ratio of 1:3 (w/v). The flask is mounted on a heating mantle and maintained at a temperature of 80 ℃ for 45 minutes, mixture of water and oil vapor passes through the condenser and it is collected in a graduated receiver. The oil layer which floats on the surface was carefully removed from the mixture residual moisture in the oil was removed by adding 0.5 g of anhydrous sodium sulfate. Final oil was transferred into glass vial and stored in the refrigerator at a temperature of 4℃. 

Experimental birds and management practices

300 – 1 day old broiler chicks (Ross 307) was used for this experiment. Upon arrival, birds were unboxed, weighed with automated digital weighing scale to obtain their initial body weight gain and randomly distributed into one of the five dietary treatment groups, each treatment group consisted of 60 birds. The birds were housed in a clean disinfected battery cage measuring 0.8 m by 0.5 m by 0.35 m (L×B×H). Brooding was done in the first two weeks using gas heaters to maintain optimum temperature. Clean drinking water and basal diets were provided throughout the experimental period. Vaccinations (Table 2) were strictly followed according to the Veterinary Regulations in Rajasthan. 

Experimental diets and design

A completely randomized design was adopted and basal diet was formulated to meet the specified nutrient requirements of broiler chickens according to NRC (1994) recommendations. The birds were distributed into 5 treatments with 6 replicates consisting of 10 birds each. The treatment group were as follows:

Treatment 1 (control): Basal diet only without Caesalpinia bonduc leaf oil 

Treatment 2: Basal diet with 0.5 mL + Caesalpinia bonduc leaf oil /kg diet 

Treatment 3: Basal diet with 1.0 mL + Caesalpinia bonduc leaf oil /kg diet 

Treatment 4: Basal diet with 1.5 mL + Caesalpinia bonduc leaf oil /kg diet 

Treatment 5: Basal diet with 2.0 mL + Caesalpinia bonduc leaf oil /kg diet 

To ensure the full dose of Caesalpinia bonduc leaf oil was consumed, daily oil requirements of each group was mixed with 100 g of feed and offered as the first meal in the morning. The remainder of the daily feed allowance was provided after the treated portion was fully consumed. 

Birds were weighed weekly in the morning before feeding to evaluate the body weight gain. Feed consumed was recorded daily by subtracting the weight of the left over from the weight of feed given. Feed to gain ratio was calculated as the ratio of feed consumed to weight gain.

Nutrient digestibility trial

Nutrient digestibility trial was carried out on the last day of the trial. 5 birds were randomly selected per treatment and transferred into a metabolic cage. Birds were allowed to adjust to their new environment for 2 days. The digestibility trial wasted for 5 days, a known quantity of feed was given to birds, total excreta were collected, weighed and oven dried at a temperature of 70 ℃ for 4 hours. Samples of feed and excreta were analyzed for dry matter, crude protein, crude fibre, ether extract and ash using CSD® near infra-red feed analyzer (Model 3400C, China), calibrated and adjusted to the manufacturer’s instruction to ensure precision in results

All data collected on growth performance and nutrient digestibility were subjected to One- way Analysis of Variance for Completely Randomized Design. Significant difference between treatment means were separated using Duncan Multiple Range Test at a probability level of p<0.05. 

Table 1: Ingredient and chemical composition of basal diet (% DM).

Starter Min-Vitamin Premix; 2.5 kg contains—vitamin A: 10,000,000 IU; vitamin D3: 4,000,000 IU; vitamin E: 27,000 IU; vitamin K: 3,000 mg; thiamine B1: 1,800 mg; riboflavin B2: 7000 mg; pyridoxine B6: 2,800 mg; niacin: 30,500 mg; vitamin B12: 20 mg; pantothenic acid: 9000 mg; folic acid: 8000 mg; biotin: 70 mg; choline chloride: 350 g; antioxidant: 115 mg; magnesium: 100 g; zinc: 70 g; iron: 13 g; copper: 8.00 g; iodine: 1.25 g; selenium: 100 mg; cobalt: 100 mg.

Finisher Min-Vitamin Premix; 2.5 kg contains —vitamin A: 10,000,000 IU; vitamin D3: 2,000,000 IU; vitamin E: 20,000 IU; vitamin K: 2,250 mg; thiamine B1: 1750 mg; riboflavin B2: 5000 mg; pyridoxine B6: 2750 mg; niacin: 27,500 mg; vitamin B12: 15 mg; pantothenic acid: 7500 mg; folic acid: 7500 mg; biotin: 50 mg; choline chloride: 400 g; antioxidant: 125 mg; magnesium: 80 g; zinc: 50 g; iron: 20 g; copper: 5 g; iodine: 1.2 g; selenium: 200 mg; cobalt: 200 mg.

Table 2: Vaccination schedule for birds.

Table 3: Phytochemical composition Caesalpinia bonduc leaf.

Table 4: Growth performance of broiler chickens fed different levels of Caesalpinia bonduc leaf oil.

a,b,c Means within the same row with different superscript differ significantly (p<0.05).

Table 5: Nutrient digestibility of broiler chickens fed different levels of Caesalpinia bonduc leaf oil.

a,b,c Means within the same row with different superscript differ significantly (p<0.05).

Table 4 reveals the growth performance of broiler chickens fed different levels of Caesalpinia bonduc leaf oil at starter and finisher phase. Variables obtained in this study follow similar trend as body weight gain, feed to gain ratio and feed consumption were significantly (p<0>

The inclusion of Caesalpinia bonduc leaf oil at up to 2.0 mL/kg diet successful improved the growth of birds over the 42 days period. The increase in nutritient digestibility suggests that the phyto-components (particularly terpenoids and phenols) enhanced enzymatic activities and intestinal health.