Potency of cassava leaf as protein source for Nile tilapia (Oreochromis niloticus)

Abstract

Cassava (Manihot esculenta, Crantz) leaves are cheap and readily available resource that can be used as a feed ingredient for Nile tilapia although they have different constituents that affect their nutritional values. The aim of the study was to examine the effects of processing methods on nutrient content of cassava leaves, digestibility, and growth performance of Nile tilapia. Eight processing methods, namely air-drying, soaking and boiling, baker’s yeast (Saccharomyces cerevisiae), rumen-fluid, molasses, yeast-rumen-fluid, yeast-molasses and molasses-rumen-fluid fermentations, were applied. One control and eight processed cassava leaf-based diets were made. The cassava leaf protein replaced 30% of crude protein (CP) from soybean cake in the control diet. The results showed that CP content in dry matter (DM) varied from 21.7 ± 0.25% (Molasses fermentation) to 30.3 ± 0.25% (Yeast-rumen-fluid fermentation). Rumen-fluid fermentation showed higher (p < 0.05) level of gross energy (21.9 ± 0.02 MJ/kg, DM) and ether extract (12.0 ± 0.21%) compared with other treatments. The apparent digestibility coefficient of CP was generally higher in the control diet (89.9 ± 0.61% in the hindgut), followed by rumen-fluid fermented diet (87.2 ± 0.61%), rumen-fluid-molasses fermented diet (86.1 ± 0.61%) and yeast-molasses fermented diet (85.3 ± 0.61%). Besides the control diet, the latter three diets also revealed the best growth rate, feed conversion ratio, protein efficiency ratio and production profitability. In conclusion, rumen-fluid, yeast-molasses, and rumen-fluid-molasses fermentation methods improved the nutritional value of cassava leaves. Diets with 30% protein from soybean cake replaced by rumen-fluid, rumen-fluid-molasses and yeast-molasses fermented cassava leaves had overall acceptable growth performance with better production outcomes for Nile tilapia farming.