Physiological Resilience and Metabolic Response of Broiler Chickens to Graded Level of Ocimum gratissimum and Vernonia amygdalina Leaf Meals as Natural Growth Promoters

This study provides a comparative assessment of the haematological and serum biochemical responses of broiler chickens fed graded levels of Ocimum gratissimum (Scent Leaf Meal SLM) and Vernonia amygdalina (Bitter Leaf Meal BLM) as natural alternatives to synthetic antibiotics. In two separate trials, a total of 300 day old broiler chicks (Ross 308) were assigned to four dietary treatments (T1: 0%, T2: 0.15%, T3: 0.30%, and T4: 0.45% inclusion) in a Completely Randomized Design. At the end of the 7 weeks (finisher phase), blood samples were collected to evaluate erythrocytic indices, immune response markers, liver enzyme activity, and lipid profiles. Results revealed that SLM significantly (P<0.05) stimulated erythropoiesis, achieving optimal packed cell volume (36.33%) and haemoglobin levels (13.80 g/dL) at the 0.30% inclusion level (T3). In contrast, birds fed BLM maintained lower haematological values, with peak PCV at 28.67% in the control group. Serum biochemistry indicated that SLM possesses superior hepatoprotective and hypolipidemic properties, significantly increasing high density lipoprotein (76.33 mg/dL) while maintaining low liver enzyme activity at high inclusion levels. Conversely, BLM inclusion at 0.45% (T4) induced significant elevations in ALT (86.11 U/L) and AST (44.37 U/L), suggesting a metabolic safety threshold at lower concentrations. Both leaf meals supported robust immune health through maintained lymphocyte counts. It is concluded that while both plants are physiologically compatible with broiler production, Ocimum gratissimum offers a higher safety threshold and more effective lipid lowering potential. For optimal performance, an inclusion level of up to 0.45% is recommended for SLM, while BLM should be restricted to a 0.30% inclusion level to avoid hepatocellular stress.