This study investigated the effects of dietary Psidium guajava leaf powder on the growth, antioxidant status, and haematological responses of Monosex Nile tilapia ( Oreochromis niloticus ) fingerlings. A 90-day feeding trial was conducted using diets containing 0%, 2%, 4%, 6%, or 8% guava leaf powder. Tilapia fed the 8% inclusion diet exhibited significantly higher weight gain, percent weight gain, specific growth rate, average daily gain, and improved feed conversion ratio and protein efficiency ratio (p < 0.05). Haematological indicators such as RBCs, Hb, PCV, MCH, MCHC, and lymphocytes increased significantly in treated groups, while WBCs were highest in the control. Antioxidant enzyme activities (GPx, SOD, GST) were elevated in the liver and kidney of fish fed guava leaf diets, with reduced lipid peroxidation (MDA). Water quality remained within optimal limits. These findings indicate that dietary inclusion of 8% guava leaf powder enhances growth and physiological resilience in Nile tilapia, supporting its potential use as a sustainable, natural aquafeed additive. • Guava leaf powder was tested at 0–8% inclusion levels in tilapia diets. • Highest growth performance occurred at 8% inclusion. • Haematological and antioxidant markers improved significantly. • Guava leaf powder reduced oxidative stress (lower MDA, H₂O₂). • Psidium guajava shows strong potential as an eco-friendly aquafeed additive.
Painkra et al. (2026) studied this question.