Detoxified Jatropha curcas kernel meal as a dietary protein source: growth performance, nutrient utilization and digestive enzymes in common carp (Cyprinus carpio L.) fingerlings

Jatropha curcas kernel meal is rich in protein; however, it is toxic. Two durations of detoxification process were investigated: 30 and 60 min; designated as J(a) and J(b), respectively. Common carp fingerlings (252 fish; 3.2 +/- 0.07 g) were fed diets: control containing fishmeal (FM); S-50, J(a50) and J(b50): 50% of FM protein replaced by soybean meal (SBM), detoxified Jatropha kernel meal (DJ(a)KM and DJ(b)KM); S-75, J(a75) and J(b75): 75% of FM protein replaced by SBM, DJ(a)KM and DJ(b)KM. Highest body mass gain, specific growth rate, metabolic growth rate (MGR) and energy production value were observed for the J(b50) group which were statistically similar to that for control group and significantly (P < 0.05) higher than for all other groups. Lowest feed gain ratio was observed in control group, which was statistically similar to than in J(b50) group. Lowest MGR, protein efficiency ratio, protein productive value and lipid production value were observed in J(a75) group. The dry matter and lipid digestibilities were statistically (P < 0.05) highest in control group and lowest in J(a50) group. Protein and energy digestibilities were statistically similar (P > 0.05) for control and J(b50) groups, and these values were highest among the groups. Highest crude protein efficiency was observed in J(b50) group, whereas lowest in J(b75) group. Relative intestinal length and hepatosomatic index were higher in plant protein-fed groups. Intestinal amylase, protease and lipase activities for control group were statistically higher (P < 0.05) than for plant protein-fed groups. Conclusively, performance of J(b50) group was similar to control group and better than other groups and, thus, is recommended as the most optimal diet for common carp fingerlings.