Chemical composition and effect of heat on organic matter- and nitrogen-degradability and some antinutritional components of Jatropha meal

Abstract

Jatropha curcas, a member of the Euphorbiaceae is a multipurpose tree of significant economic importance because of its several industrial and medicinal uses. The kernel to shell ratio of J. curcas seeds was 63:37 and the kernels contained about 580 g kg −1 oil. The oil-free kernels of J. curcas had crude protein content of about 580 g kg −1, however 24 h in vitro rumen nitrogen degradability (IVDN) was very low (29 to 43%). In addition, the meal had high activity of trypsin inhibitor (TIA, 19 to 21 mg trypsin inhibited g −1 sample) and phytate (ca 10%). Lectins (a minimum of 66.7 mg ml −1 assay produced agglutination) and saponins (2.6% as diosgenin equivalent) were also present. Tannins were not detected and the phenolic content was negligible (0.2 to 0.4% as tannic acid equivalent). Effect of several heat treatments (moist: 100°C, 67% moisture; 130 and 160°C, initial moisture 80%, dry: 130 and 160°C, combination of moist and dry heating: 100°C, 67% moisture, 60 min followed by dry heating at 160°C) on nutritive value and deleterious components of partially defatted (PD, about 23% residual oil) and defatted (D, about 1.5% residual oil) Jatropha meals were studied. Some treatments which could be promising for monogastrics were: (i) moist heating (67% moisture) at 100°C for 60 min which increased IVDN of PD and D meals to 66.5 and 67.4% respectively and decreased TIA to about 5 mg trypsin inhibited g −1 sample; and (ii) moist heating (80% initial moisture) at 130°C for 30 min which increased IVDN of PD and D meals to 55.2 and 73.3% respectively and decreased TIA to about 4 mg trypsin inhibited g −1 sample. For ruminants, dry heating at 160°C for 120 min might be advantageous as IVDN decreased to 23.7% for PD meal and to 38.6% for D meal. The TIA of these treated meals was about 4 mg trypsin inhibited g −1 sample. Presence of oil was found to decrease the effect of heat in increasing IVDN and inactivating trypsin inhibitors. The levels of other antinutritional factors did not decrease by the treatments studied. The pepsin insoluble nitrogen in the moist heated samples were only 4 to 6% of the total nitrogen and those in the dry heated samples were from 8 to 15%. The calculated organic matter digestibility and metabolizable energy and IVDN for D Jatropha meal following heat treatment (80% initial moisture, 130°C, 30 min) were: 82.9%, 11.8 MJ kg −1 and 73.3% respectively which were lower by 5% units, 2.5 MJ kg −1 and 7.6% units respectively compared with soyabean meal.