Removal of antinutrients from bitter cassava leaves and its effect on feed quality for Nile tilapia
1992
Shukla, Kumar Arvind
Bitter cassava (Manihot esculenta) leaf was investigated for the presence of antinutrients namely, trypsin inhibitor (TI), cyanogen, phytate, tannin and saponin. Treatments namely, boiling (T1), soaking (T2), alkali treatment (T3), drying (T4) and ensiling (T5) were evaluated for their efficacy to remove these antinutrients. On the basis of chemical analysis the treatments were selected and differently treated cassava leaf meal (CLM) based diets were prepared. These diets were evaluated for their suitability in fish grow-out experiment. The amount of TI, HCN and phytic acid in untreated leaf were found to be 377.6, 42.0 and 803.3 mg/kg, respectively. Tannin and saponin contents were found to be 2.17 and 2.53 %, respectively. Efficiency of the soaking and alkali treatment for removal of most of the antinutrients was generally high. To remove TI and HCN, alkali treatment, drying and ensiling, however, were found to be equally good. Saponin and phytic acid were best removed by boiling while tannin removal was most efficient by soaking followed by alkali treatment. Ensiling resulted in increased tannin content. The treatments selected for the grow-out experiment were drying, soaking, alkali treatment, and boiling. The treated dry leaf was powdered and isonitrogenous diets were prepared and fed to Nile tilapia for 42 days. None of the treatments resulted in a reduction of crude protein content of CLM but the ash content was significantly reduced after every treatment except drying. In comparison to control diet (D1) fed fish the growth rate (GR) and specific growth rate (SGR) of fish was very low when fed CLM based diets. However, soaked and alkali treated CLM based diets showed comparatively better results (0.44 and 0.40 g/day GR, respectively).
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