Ameliorative Effects of Dietary Ocimum gratissimum Leafmeal on African Catfish, Clarias gariepinus Subjected to Pathogenic and Transportation-Induced Stress

The primary aim of this project is the use of functional feed supplements to ameliorate or reduce the effects of stressors rather than using chemicals that could be harmful and expensive. Specifically, assessment of the ameliorative effect of locally available phytogenic product, Ocimum gratissimum on the negative effects of stress in African catfish production was carried out in a study that lasted for 70 days. Five experimental diets were formulated, at different inclusion levels of O. gratissimum , as 0.00 g (control), 0.05 g, 0.10 g, 0.15 g, 0.20 g per 100 g of diet denoted as T1 (control), T2, T3, T4, and T5 respectively. At the end of the feeding trial, stress-induced treatments of experimental fish were done using pathogenic and transportation stressors. Zootechnical parameters in terms of growth and nutrient utilization were evaluated. Physiological stress assessment (Aspartate transaminase, AST and Alanine transaminase, ALT) and stress biomarkers (cortisol and glucose) were carried out using liver and blood samples from experimental fish. Results showed that zootechnical parameters were significantly (P < 0.05) enhanced with increasing supplementation levels of O. gratissimum. There were better performances in the growth and nutrient utilization indices like weight gain, specific growth rate, protein efficiency and feed conversion ratio as the level of O. gratissimum was increased to 0.15 mg/g in the diets. Curvilinear trends were recorded with a second degree polynomial regression model depicting a strong relationship between SGR and O. gratissimum supplementation in fish diet followed by adverse responses when increased to 0.20 mg/g in the diet. There were significant reduction in stress parameters with increasing supplementation levels of O. gratissimum leaf extract in the diets. The best supplementation level of O. gratissimum was 0.15 mg/g in T4. From the above deductions, this study confirmed the positive ameliorating effects of O. gratissimum on the African catfish during stressful episodes.