Aqueous Extract from Gmelina arborea Leaf as a Functional Water-Based Supplement for Broiler Chickens in the Tropics: Integrated Mechanistic Framework for Effects on Growth Performance and Haematological Health

The escalating restrictions on antibiotic growth promoters in poultry production have intensified the search for sustainable, plant-derived alternatives that maintain productivity whilst safeguarding animal health and food security in tropical contexts. This study evaluated the efficacy of aqueous extract from Gmelina arborea leaves administered through drinking water supplementation on growth performance and haematological health of broiler chickens reared in a tropical environment. One hundred and forty-four (day-old) broiler chicks (Ross 308) were randomly allocated to four treatment groups using a completely randomized design with three replicates of twelve birds each. Treatments comprised a control group receiving no supplementation and three supplementation groups receiving 10 ml, 20 ml, and 30 ml per litre of aqueous Gmelina leaf extract (AGLE) in drinking water. After an initial 28-day brooding phase, birds entered the 28-day finisher phase during which dietary treatments were administered. Growth performance parameters measured included initial body weight, final body weight, total weight gain, average daily weight gain, total and average daily feed intake, feed conversion ratio, and water consumption. Haematological analyses encompassed red blood cell count, packed cell volume, haemoglobin concentration, white blood cell count, and differential leucocyte counts. Results demonstrated non-significant differences in growth performance indices across treatments. However, AGLE supplementation significantly enhanced haematological parameters, with packed cell volume and red blood cell counts increasing progressively across dose levels whilst haemoglobin concentrations achieved maximal elevation at the 30 ml dose. White blood cell counts demonstrated dose-dependent suppression without immune compromise. These findings suggest that AGLE, rich in bioactive compounds including saponins, glycosides, flavonoids, and tannins, may function as an effective non-antibiotic supplement supporting haematopoietic function through enhanced iron bioavailability and antioxidant-mediated erythrocyte protection. The study established a foundation for integrating locally-sourced, non-food plant resources into antibiotic-free poultry production systems aligned with tropical sustainability imperatives and One-Health principles.