The Efficacy of Selected Plant Materials in Formulated Diets for Nile Tilapia, Oreochromis niloticus (L).

Abstract

A study was carried out to determine the suitability of selected plant materials to replace animal proteins from the conventional diets used to culture O. niloticus in Kenya. The research done at Sagana Aquaculture Centre was aimed at formulating cheap diets using Cassava Leaf Meal (CLM), Boiled Tea Leaf Meal (BTLM) or pawpaw Leaf Meal (PLM). Each test ingredient replaced Fresh Water Shrimps Meal (FSM) from a control diet in an 8-week feeding trial using O. niloticus fingerlings both in aquaria (initial mean weight 12.36±1.1g fish-1) and hapas (initial mean weight 10.55g fish-1). Fish growth performance, resulting whole body proximate composition (WPC), and the effects on the Hepatosomatic index (HSI) were used to assess the efficacy of the substitutions. Four isonitrogenous (300g/kg) practical diets were formulated to contain 0%, 25%, 50% or 100% of the plant ingredients. Experimental fish were fed 10% of their body weight in triplicates. In hapas, increased dietary BTLM had no significant effect on the SGR (g/day) and PWI but inclusion beyond 25% BTLM caused a significant decrease (P<0.05) in FBW. Increasing BTLM caused poor growth in aquaria. Diets with BTLM had no significant effect on carcass moisture level for fish in hapas, but at 50%BTLM inclusion HSI increased significantly. In aquaria increased inclusion of BTLM had no significant effect on the whole body moisture composition. Full replacement with BTLM caused a significant decrease in carcass crude protein (CP), while 25%BTLM caused a significant decrease (P<0.05) in WB ash. In aquaria inclusion beyond 25%BTLM significantly increased in HSI. In hapas increased CLM caused a significant decrease (P<0.05) in SGR (g/day) and percentage weight increase (PWI) but had no significant effect on final body weight (FBW) up to 50%CLM. In aquaria 25% CLM caused a significant increase in SGR (g/day) and inclusion beyond 25% CLM caused a significant decrease in FBW. Inclusion of CLM beyond 25% CLM caused a significant increase (P<0.05) in carcass moisture composition in hapas while in aquaria no significant effect was observed on carcass moisture and carcass CP up to 50%CLM, but a significant increase in carcass moisture was observed at 100%CLM levels. CLM had no significant effect on HSI up to 50%CLM inclusion in hapas. Increased in PLM had no significant effect (P>0.05) on growth performance. In hapas, 25%PLM caused a significant increase (P<0.05) in carcass moisture while inclusion levels of 50%PLM and 100%PLM significantly decreased (P<0.05) carcass ash. PLM had no significant effect (P<0.05) on HSI in hapas. In aquaria, PLM had no significant effect on the carcass moisture and ash but increased levels caused a significant (P<0.05) decrease in the HSI. In conclusion all test ingredients could partially be used to replace Freshwater shrimp meal from the conventional diet used to culture O. niloticus except pawpaw leaf meal, could wholly substitute freshwater shrimp meal.