Studies on detoxification of Jatropha press cake and preliminary feed testing in tilapia (Oreochromis niloticus L.)
2009
Espiritu, B.M. | Nuñez, S.F. | Willauer, L.B. | Demafelis, R.B., Philippines Univ. Los Baños, College, Laguna (Philippines)
Jatropha curcas meal has crude protein content of 53 to 58%. The press cake, however, has been found to be very toxic to fish, rats and chickens. In this study, Jatropha press cake was detoxified using heat treatment, solvent extraction and fermentation with mixed microbial inoculants for three weeks. Using tilapia fingerlings (Oreochromis niloticus L.), a two-week experiment was conducted to evaluate the toxicity and nutritional quality of the treated Jatropha press cake as fish feeds. Fingerlings were randomly distributed in eight treatment groups and fed the following diets: T1 (standard diet for commercial feed), T2 (fermented cake), T3 (50% commercial feed + 50% fermented cake), T4 (methanol-treated cake), T5 (50% commercial feed + 50% methanol-treated cake), T6 (heat-treated cake), T7 (50% commercial feed + 50% heat-treated cake), and T8 (raw Jatropha press cake). The body weight gain (BWG%) and specific growth rate (SGR%) in T1 and T3 were statistically similar, and both were significantly higher than those of the other groups. Feed intake with raw Jatropha meal in diet was significantly reduced for all treatments and fish experienced body weight loss. This was mainly attributed to the presence of phorbol esters, a toxin found in raw Jatropha press cake. Percent mortality based on tilapia test was used as the index of toxicity of treated and untreated press cake in this evaluation. Highest mortality of 46.67% was observed in those fed with raw press cake. T3 gave the results closest to that of T1 for all feeding parameters such as body weight gain, specific growth rate and daily food consumption. Fermentation with mixed bacterial inoculants seemed to be the best method for detoxifying Jatropha press cake for use as fish feed.
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