Lack of affordable feeds is one of the major constraints facing small-scale
fish farmers in Tanzania. This study evaluated the suitability of moringa
leaf meal (MLM), cassava leaf meal (CLM) and cassava root meal (CRM) as
novel ingredients in Nile tilapia, Oreochromis niloticus diets. Each of the
ingredients was processed in an attempt to remove the most significant
antinutritional factor. A series of five experiments was conducted in a
recirculation system using juvenile O. niloticus. The fish were fed
isonitrogenous (30g 100g-1), isolipidic (10g 100g-1) and isoenergetic (18 kJ
g-1) diets containing graded levels of the processed ingredients to their
apparent appetite but not exceeding 10% of their body weight for a period
of 8 weeks.
Processing led to the removal of 0.3% of saponin from MLM and 60% and
90% of hydrogen cyanide from CLM and CRM respectively. The contents of
other inherent antinutritional factors such as phenols, tannins and phytic
acid were little affected. Processed MLM, CLM and CRM had
31.1/29.0/1.5g 100g-1 of crude protein, 5.9/10.2/2.4g 100g-1 of crude
fibre and 20.1/19.7/15.8k Jg-1 of gross energy. The content of sulphur
amino acids was higher in CLM (0.47%) than in MLM (0.23%). Digestibe
protein and digestible energy was higher in MLM (25.71g 100g-1/15.44kJ g-1)
than in CLM (12.71g 100-1/9.16kJ g-1). CRM had a digestible energy
content of 13.5kJ g-1.

Inclusion of either of the leaf meals, even at the lowest level of 15g 100g-1
of total dietary protein, led to a significant reduction in feed intake, growth
and feed utilisation. Liver and small intestine did not show any
histopathological changes which could be linked to dietary treatment.
Conversely, cassava root meal could replace up to 75% of wheat meal in
the diet without significantly affecting performance. The performance of
leaf meals was marginally improved by a combination of blending and
feeding stimulants, whereby a blend containing 1 part MLM and 2 parts
CLM could provide up to 20g 100g-1 of dietary protein without significantly
reducing performance. Biological and economic performance of practical
diets containing 30-50g 100g-1 of dietary protein from moringa and
cassava blends (LMB) with feeding stimulants was significantly lower than
a fishmeal-meal based diet (FM) but comparable to a soybean meal-based
diet (SBM).
The suitability of MLM and CLM as novel protein sources in O. niloticus
diets will depend on 1) improving reduction/removal of inherent
antinutritional factors in MLM and CLM as well as improving digestibility
of CLM. On the other hand, the suitability of CRM as a carbohydrate
energy source will depend on the availability of cost effective protein
sources due to its low protein content.