Biological and economic performance of peanut-based meals As alternatives to dietary fishmeal in pond cultured Nile Tilapia (Oreochromis niloticus L.) In Uganda

Abstract

Increasing price of dietary fishmeal is offsetting the excellent growth and yield induced in farmed Nile tilapia subsequently reducing the corresponding cost-effectiveness. Replacement of the dietary ingredient with better or comparable substitutes has become necessary in many countries including Uganda. In light of the phenomenon, a study was conducted in Busoga sub-region of Eastern Uganda to evaluate the biological and economic performance of pondcultured Nile tilapia (Oreochromis niloticus L.) fed on peanut-based meals as alternative to dietary fishmeal. Sample surveys supplemented by field experiments attained all the specific objectives of the study from January 2016 to March 2017. The specific objectives of the study related the following performance indicators in Nile tilapia fed on the test diets; biomass production (g/pond), Feed Conversion Ratios, Relative Growth Rates (%), Net Fish Yields (g/pond), Survival Rates (%), Economic Conversion Ratios and Profit Indices. The surveys that valuated the test feeds and fish products occurred in sampling units in local commodity markets in Iganga municipality and along the main roads network respectively. The fish pond input and output valuations (USD/Kg) were conducted directly and indirectly respectively. The field experiments aimed at measuring targeted responses induced by test diets in Nile tilapia. Each of the two experimental sites at Busoga University farmland consisted of rectangular shaped earthen ponds. Two experimental sites A and B were stocked in the dry and wet seasons respectively. The replication of Site A at Site B aimed at mitigating the effect of weather on fish production. Forty-eight mono-sex fish fingerlings were stocked in sixteen pond units of uniform size (3.0 x 4.0 x 1.0 cubic meters) at each site. Among the stocked ponds, one acted as a fish reserve pond for mitigating the risk of fish loss in the earthen ponds. Mean body weights at stocking were 22.2 and 21.7 grams for the sites A and B respectively. Test diets were Iso-caloric throughout the experiments (5.3627 Kcal/g) and isonitrogenous; 30% and 25% Crude Protein for the first twelve and latter weeks respectively. Dietary treatments included the fishmeal-based diet (control) and two peanut-based diets; peanut meal and mixed plant meal-based diets. The locally available commercial feed for grow-out Nile tilapia containing 25% Crude Protein was the control diet throughout the feeding trials. The results indicated that only unionized ammonia affected fish biomass production negatively. Survival Rates in Nile tilapia were the only performance indicators that were insignificantly different (p 0.05) across all the dietary treatment groups. Other Insignificant differences (p 0.05) among other indicators of performance were restricted were restricted the fishmeal and mixed plant-based diets. With exception to the Survival Rates, the peanut-based diet exhibited significantly poorer (p 0.05) results than the fishmeal-based diet. The lack of significant differences (p>0.05) across all tested biological and economic performance indicators implied that the mixed plant meal based and fishmeal-based diets exhibited comparable performances. Therefore, among the peanut-based meals, only the mixed plant-meal should completely substitute the conventional fishmeal-based diet in the pond cultured Nile tilapia in Uganda.