38 June 2012 Jatropha meal, a promising plant protein source in aquafeed development Vikas Kumar1, Olesia Gavryliuk2, Amit Kumar Sinha1, Debtanu Barman*3, Eef De Clercq1, Apu Das4 and Sagar C. Mandal5 Jatropha curcas (L.) (physic nut) is a multipurpose, drought resistant shrub or small tree that normally reaches a height of 3-5 m, but can reach a height of 8-10 m under favorable conditions (Figures 1, 2 and 3). It is found throughout the tropics and subtropics. It is a hardy plant, thriving on degraded land and requiring limited amounts of nutrients and water. Its seeds have been extensively investigated as a source of oil. The Jatropha kernel meal is obtained after the oil is extracted. The seed kernel contains about 60 percent oil that can be converted into biodiesel fuel of high quality upon trans-esterification and used as a substitute for diesel fuel (Makkar et al. 2007). The kernel meal obtained after oil extraction is an excellent source of nutrients, containing 58 to 65 percent crude protein (Kumar et al. 2010a). Furthermore, the levels of essential amino acids (EAA), except lysine, are higher in Jatropha kernel meal than soybean meals (Kumar et al. 2010a). However, the presence of high levels of antinutrients (Makkar et al. 2008) and major toxic components (Makkar et al. 1997) restrict their use in fish feed. Subsequently, besides being a source of oil, J. curcas also provides a meal that serves as a highly nutritious and economic protein supplement in animal feed, provided the toxins are removed (Becker and Makkar 1998). Jatropha plant can yield up to 5 t seeds per year from one ha of plantation, which can produce approximately 1 t of kernel meal rich in protein (Makkar and Becker 1997). This means that there is a possibility of producing enough Jatropha kernel meal to meet the growing demand from aquaculture. Constraints in Using Jatropha Kernel Meal Toxic and non-toxic genotypes of J. curcas have been reported in cultivation practices (Makkar and Becker 2009). The nontoxic genotype exists only in Mexico, while the toxic Fig. 1. A mature Jatropha curcas tree. genotype is prevalent throughout the rest of the world. The use of Jatropha meals prepared from the toxic genotype in animal nutrition is limited because of the presence of antinutritional components and toxic factors (Table 1). The major antinutrients are trypsin inhibitors, lectin, and phytate. The main toxic factor present is phorbol esters (PEs), which are highly toxic to animals. The levels of trypsin inhibitor and lectin are similar to those in soybean meal and the level of phytate (9.4 percent) is approximately three times greater than in soybean meal. The kernel has greater crude protein, 2228 percent and oil content of 54-58 percent (Makkar et al. 1998). Furthermore, it was shown that the force feeding of Jatropha meal containing PEs displayed toxicity in mice (Li et al. 2010) rats and goats (Goel et al. 2007). Similar results have also been reported in fish (Becker and Makkar 1998). The major organs affected were intestines, liver and kidney. On the other hand, nontoxic J. curcas kernels are also rich in oil (55-58 percent) and protein (26-29 percent) (Makkar and Becker 2009). The nontoxic genotype does not have phorbol esters but contains the trypsin inhibitors, lectin and phytate, at the same levels as the meal from the toxic genotype. However, the nutritional value of meal obtained from the nontoxic genotype, after heat treatment, is very high as evaluated in fish (carp) and rats (Makkar and Becker 1999). Thereby, it could be an excellent protein-rich ingredient in feeds of ruminant and monogastric animals, including fish. However, removal of toxins to a safe level is, therefore, necessary before Jatropha meal can be used as animal feed. Chemical Composition of Jatropha Meal The content of crude protein (CP), lipid, ash, neutral detergent fiber (NDF), total sugar and starch in Jatropha kernel meal are similar for the two genotypes (Table 2, Makkar
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