The nutritional value of Jatropha curcas kernel (JCK) can be improved through different processing methods; however, when using a thermal treatment, optimization of the process is needed to prevent denaturation of nutrients. In this study, JCK was toasted for varying durations (0, 10, 20, and 30 min) and nutritionally evaluated. The implication of feeding Clarias gariepinus with dietary inclusions (35% CP; 315 kcal g-1) of the toasted JCK was also reported. The results obtained suggest that prolonged duration of toasting improved the nutritional characteristics of the JCK until the 20th min. Beyond this time, the protein content and essential amino acids are reduced. However, the antinutrients continuously decreased with prolonged processing. The growth, carcass analysis, and haematology of the fish groups fed toasted JCK at varying duration also did better than those fed raw JCK. Importantly, the performance tends to reduce for those fed JCK toasted beyond 20 min. The estimated cost of producing 1 kg of the fish also substantially reduced with feeding the processed JCK than feeding raw JCK. Histological examination of the intestine and liver tissues further revealed fewer signs of histopathological degeneration for fish-fed processed JCK compared to the control. It was concluded that the processing of JCK by toasting should not exceed 20 min to improve the nutritional composition of the feed ingredients and their dietary utilization by fish.
Keywords: African Catfish; Antinutrients; Non-conventional feedstuff; Toasting.