Effects of Dietary Detarium microcarpum Stem-bark Extract on Erythrocyte and Leucocyte Variables in Nile Tilapia (Oreochromis niloticus)
Abstract
Plant-derived feed additives are increasingly investigated as locally available tools for sustainable aquaculture, but their physiological effects require careful assessment. The objective was to determine whether graded dietary supplementation with a hydroethanolic Detarium microcarpum stem-bark extract was associated with detectable changes in erythrocyte and leucocyte variables in Nile tilapia (Oreochromis niloticus). A 90-day completely randomised feeding trial was conducted in Loumbila, Burkina Faso, with haematological analyses performed in Bobo-Dioulasso in 2026. A total of 180 fingerlings (initial body weight 7.49 ± 1.43 g) were allocated to 12 tanks (15 fish/tank) and fed an unsupplemented control diet (RT) or diets containing 200, 300, or 400 mg dried extract/kg feed (R1, R2, and R3, respectively), with three replicate tanks per treatment. After 90 days, three fish per tank (n = 9/treatment) were sampled. Red and white blood cell counts, haemoglobin, haematocrit, erythrocyte indices, lymphocytes, and neutrophils were measured using a Sysmex XN-550 analyser, and dietary effects were assessed by nested analysis of variance. No significant dietary effect was detected for any of the nine haematological variables; treatment-effect P values ranged from .10 to .80. Red blood cell counts ranged from 1.37 ± 0.51 to 1.84 ± 0.52 ×10⁶/µL, haemoglobin from 7.17 ± 2.47 to 9.62 ± 2.62 g/dL, and haematocrit from 23.00 ± 7.10 to 30.96 ± 9.40%. White blood cells and lymphocytes were numerically highest in R2 but showed substantial within-treatment variability, while mean neutrophil-to-lymphocyte ratios remained descriptively similar (0.214-0.270). Under the conditions tested, dietary D. microcarpum stem-bark extract at 200-400 mg/kg did not produce a detectable adverse haematological effect. The numerical leucocyte changes do not establish immunostimulation and require confirmation using validated fish-specific cell-counting methods and complementary immune biomarkers.