The positive impact of partial substitution of fish meal by a meal mixture of duckweed and mealworm larvae on the diets of Nile tilapia fry (Oreochromis niloticus Linnaeus, 1758)

Abstract

In ordre to promote aquaculture in the south of the country, and specifically, to reduce the cost of feeding farmed fish, this study was carried out to evaluate the effect of partial replacement of fishmeal with a mixture of duckweed meal (DWM) and mealworm larvae (WLM) on growth performance, feed utilization and carcass composition of Nile tilapia. Eight-week feeding experiment was conducted on fry of O. niloticus (average initial weight: 0.87 ± 0.23 g). Four isoproteic diets (38.52 ± 0.11% crude protein) comprising control diet D0 and three test diets (D1 to D3) were formulated and tested in triplicates. To satisfy EAA requirements in test diets, the ratios 1: 5; 2: 4 ; 4: 2 between DWM and WLM were used respectively in partial replacement for fishmeal. No significant differences (P > 0.05) were observed in survival, growth and feed utilization. On the other hand, the compositions of the carcasses showed strong significant differences (P < 0.05) except ash contents. The carcass lipid increased proportionally with the inclusion of WLM, but the reverse was true for the moisture content. However, the high contents of retained proteins were obtained in the ratios 0 : 0 and 4 : 2 between D0 and D3. It is concluded that fishmeal could be replaced by a meal mixture of DWM and WLM up to the proportion (4 : 2, respectively) in the feed of O. niloticus without adverse effects on growth and nutrient utilization and most importantly, reduce the cost of production up to 29.8% which would have a positive impact on post-feeding and therefore the financial management of an aquaculture farm.