INFLUENCE OF BITTER LEAF EXTRACT ON NILE TILAPIA GROWTH, HEMATOLOGY, AND HEAT STRESS RESPONSE

Abstract

Herbal supplements are suitable for improving growth, health of fish and increasing tolerance to environmental perturbations. Cost of formulated feed, disease outbreak and hypoxic related stress issues are major challenges confronting tilapia production. In this study, the effects of the bitter leaf (Vernonia amygdalina) extracts (BLE) on growth, hematology, liver health and resistance to heat stress were investigated in Nile tilapia (Oreochromis niloticus). Experimental fish of average weight 30 ± 1 g were puts into 4 groups each for a respective treatment and fed with diets to include a control (0 % BLE), and BLE supplemented diets at 1% BLE, 3% BLE and 5% BLE for 8 weeks in circular concreate tanks. Upon termination of the experiment, growth performance (i.e. mean weight gain (WG), viscerosomatic index (VSI), hepasomatic index (HSI) and feed conversion ratio (FCR) amongst others), hematology (i.e. red blood cell, white blood cells, leukocyte, haemoglobin, and hematocrit amongst others), liver enzyme activity (i.e. aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase), plasma chemistry to include total protein (TP) and albumin (ALB amongst others) and on hematological parameters also after heat stress treatments were sampled using appropriate tools and methods. One-way ANOVA and Duncan multiple range test were used to determine differences in growth, hematological, stress response, and toxic parameters using IBM SPSS at (P<0.05). The end results indicated that tilapia fed diets enriched with BLE in the range of 1% - 5% BLE were superior in the growth indices measured compared to the control group with 1% BLE exhibiting the best effects. Hematology and plasma chemistry showed similar results with 1% BLE presenting the best of results. However, it is worth nothing that increasing level of BLE showed a decreasing trend yet significantly high in comparism to the control group. Increased levels of AST, ALT and ALP were observed in the first 4 weeks but were significantly lower at 8 weeks in all BLE groups compared to the control suggesting initial tolerance and hepato-protectiveness of BLE in fish. The hematological indices investigated after exposure to heat stress test revealed that fish fed BLE supplemented diet could help increase tolerance to heat stress than those fed the control diet. In summation, the results suggest that BLE inclusion particularly at 1% BLE has the potential to improve growth and health of tilapia. Palatability and digestibility test is recommended in future trials to help understand and improve feed acceptance of fish fed with BLE supplements.