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Summary Jatropha platyphylla is a multipurpose and drought-resistant shrub, available in Mexico, locally known as ‘sangregrado’ and belonging to the family Euphorbiaceae. Its seeds are rich in oil and protein and do not contain the main toxin, phorbol esters present in other Jatropha species. Jatropha platyphylla kernel meal (JPKM) obtained after oil extraction contained 70–75% crude protein (CP); however, it contained phytate, lectin and trypsin-inhibitor. The levels of essential amino acids (except lysine) were higher in JPKM than in soybean meal (SBM). Using Nile tilapia (Oreochromis niloticus) fingerlings a 12-week experiment was conducted to evaluate the nutritional quality of the heated JPKM and compare with that of SBM and fishmeal. Fingerlings (15 fish; average weight 13.7 ± 0.21 g) were randomly distributed in three treatment groups with five replicates. Fish were fed three isonitrogenous diets (CP 36%): control diet containing fishmeal-based protein and two other diets replacing 62.5% fishmeal protein with JPKM (Jatropha group) and SBM (Soybean group). The growth performance, feed conversion ratio, protein efficiency ratio, protein productive and energy retention did not differ significantly among the three groups. A lower apparent lipid conversion was observed in the plant protein-fed group than in the control group. RBC count, haematocrit and blood glucose contents were higher in plant-protein fed groups than control group. Other haematological parameters (WBC count, haemoglobin, mean cell volume: calcium and sodium ions, total bilirubin and urea–nitrogen in the blood) and metabolic enzymes (alkaline phosphatase and alanine transaminase) activities in blood did not differ significantly among the three groups. The results from the present study established that JPKM is a promising and good quality protein source for Nile tilapia feed.

Summary Jatropha platyphylla is available on the pacific coast from Sinaloa to Michoacan including the Nayarit and Jalisco states in Mexico. The seeds of J. platyphylla are rich in oil and protein, and the kernel meal (JPKM) prepared after oil extraction contains 70–75% crude protein (CP). Contents of essential amino acids (except lysine) are higher in JPKM than in soybean meal (SBM). Phorbol-esters, the main toxin present in most Jatropha species is absent in J. platyphylla. Heat-treated JPKM (H-JPKM) was evaluated as a protein supplement in tilapia feed and compared with that of SBM and fish meal (FM). Nile tilapia (Oreochromis niloticus L.) fingerlings (15 fish; av. body mass 13.9 ± 0.17 g) were randomly distributed in three groups with five replicates each. A 12-week experiment was conducted in a respirometer system to evaluate the growth performance, nutrient utilization and energy budget. Nile tilapia fingerlings were fed three iso-nitrogenous diets (36% CP): Control containing FM, and Jatropha and Soybean diets in which 62.5% of FM protein was replaced by H-JPKM and SBM respectively. The growth performance, feed conversion ratio, protein efficiency ratio, apparent lipid conversion and energy retention did not differ significantly among the three groups. Higher protein productive value was observed in plant protein fed groups. Average metabolic rate, energy expenditure per g protein fed and retained in the body did not differ significantly among the three groups. Conclusively, Nile tilapia fed plant protein (heated JPKM and SBM) and FM protein-based diets exhibited equal average metabolic rate which indicate that JPKM can be used as a protein source in aqua feed.