Isolation of phytate from Jatropha curcas kernel meal and effects of isolated phytate on growth, digestive physiology and metabolic changes in Nile tilapia (Oreochromis niloticus L.)

Jatropha curcas seeds are rich in oil and protein. The oil is used for biodiesel production. The defatted Jatropha kernel meal obtained after oil extraction is rich in protein (58-66%) and phytate (9-11%). The phytate rich fraction was isolated from defatted kernel meal using organic solvents (acetone and carbon tetracholride). It had 66% phytate and 22% crude protein. The fingerlings (n = 50, 16.2 ± 0.64 g) were randomly distributed into five groups containing 10 replicates and fed iso-nitrogenous diets (crude protein 36%): control diet containing casein and gelatin as proteins; control diet containing 1.5% and 3% Jatropha phytate (PWP_1.5 and PWP₃, respectively); and control diet containing 1.5% and 3% Jatropha phytate supplemented with phytase (1500 FTU/kg) (PWP_{1.5 + Phytase} and PWP_{3 + Phytase}, respectively). Significantly lower (P < 0.05) growth and feed utilization in PWP_1.5 and PWP₃ groups than for control and both phytase containing groups were observed; whereas feed gain ratio exhibited opposite trend. Protein and lipid digestibilities of the diets, amylase and protease enzyme activities in the intestine were significantly higher (P < 0.05) in PWP_{1.5 + Phytase} and PWP_{3 + Phytase} groups than for PWP_1.5 and PWP₃ groups. Lowest red blood cell counts, and hemoglobin and hematocrit concentrations were observed in PWP₃ group which were not statistically different to those for PWP_1.5 group, but were significantly (P < 0.05) lower than those for all other groups. Highest albumin, globulin and total protein concentrations were observed in PP_{3 + Phytase} group and lowest in PWP_1.5 group; and values for the latter were statistically similar to those for control group. Calcium, phosphorus and glucose concentrations in blood and cholesterol concentration in plasma were significantly lower (P < 0.05) in the phytate enriched groups compared with control and phytase treated groups (PP_{1.5 + Phytase} and PP_{3 + Phytase}). Higher (P < 0.05) alkaline phosphatase activity was observed in phytase supplemented groups compared with that in non-supplemented groups which (PP_{1.5 + Phytase}) was statistically similar to that in control group, whereas alanine transaminase activity in blood exhibited opposite trend. In conclusion, Jatropha phytate present in DJKM is an antinutrient and addition of phytase in the diet containing DJKM is recommended.