Nutritional evaluation of plant ingredients for diets of Tilapia rendalli in NkhataBay, Northern Malawi

Modern fish culture requires the reduction of the cost of feeds which can partly be achieved by minimal use of dietary animal protein. This study assessed the nutritional potential of locally available plant based feedstuffs from Mpamba EPA in NkhataBay district; northern Malawi. The main objective was to isolate those that can be used as ingredients for formulation of affordable fish diets to increase pond based fish production in Malawi. The following plants were used in the study: cassava (Manihot esculenta) peels (CP) and leaves (CL), pawpaw (Carica papaya) leaves (PL), sweet potato (Ipomea batatus) leaves (SPL), peels (SPP), and tubers (SPM), jackfruit (Artocarpus heterophyllus) (JK), mexican fire plant (MFP) (Euphorbia heterophylla),cocoyam leaf meal (CYM) black jack (BJ) (Bidens pilosa), banana (Musa balbisiana) leaves (BL), maize (Zea maize) bran (MZB), and akee (Blighia sapid) leaves (AK). Proximate analysis was conducted to generate information for selection of potential plant ingredients to be used in the formulation of four diets of Tilapia rendalli. In addition, a digestibility experiment was also conducted on juvenile Tilapia rendalli to evaluate four diets formulated from the selected plants at NkhataBay fisheries Laboratory for 21 days. The four diets were designated as treatment 1 to 4. Treatment 1 comprised of (CL,BJ,MZB,SPM,SPL,CF,CO), treatment 2 (CL,CYM,MZB,SPM,SPl,CF,CO) treatment 3( CL, CYM,BJ,SPM,SPL,CF,CO) and treatment 4 (CL, CYM,BJ,MZB,SPL,CF,CO) .The experiment was laid out in a Completely Randomized Design (CRD) using glass aquaria with each diet replicated three times. Data for both proximate and digestibility experiments was analyzed using Analysis of Variance (ANOVA) at P= 0.05 using SPSS and R-software’s respectively. Results showed that cassava (Manihot esculenta) leaves, black jack (Bidens pilosa) and cocoyam (Caladium bicolor) had the highest levels of crude protein recording 21.17±0.56%, 24.35±0.7 % and 24.28±0.11%, respectively which were significantly different (P<0.05) from each other and other plant ingredients. vi Energy levels ranged from 8.78 kJ/g to 29.7 kJ/g for sweet potato leaves and cassava peels respectively. In general all plant feedstuffs had low levels of crude fiber ranging from 3.78±0.20% to 16.84±0.26%. Digestibility experiment results showed that there was a significant difference (P<0.05) in protein digestibility coefficients among different plant diets, however, diets 1 and diet 3 did not differ statistically (P>0.05) in digestibility coefficients. Apparent digestibility coefficients for energy (21.2 kJ/g to 43.44 kJ/g) and fat (54.29%-67.78 %) were higher than those of crude protein (24.15%-31.44). Depending on their availability and competition for other uses, most of the plant ingredients analyzed demonstrated potential for use in Tilapia rendalli feed. Information on nutritional and digestibility values of plant ingredients and diets will provide good nutritional indicators for the development of a system for selecting ingredients for inclusion in Tilapia rendalli diets.