The use of jack bean ( Canavalia ensiformis Leguminosae) meal as a partial substitute for fish meal in diets for tilapia ( Oreochromis mossambicus Cichlidae)

Abstract

The use of jack bean ( C. ensiformis) meal in diets for O. mossambicus was tested in two experiments. The first was designed to determine the effects of protein from jack bean meal treated by autoclaving for 30 min at 125°C and 15 psi, as a partial substitute for protein from fish meal. The percentages of dietary protein from jack bean meal were 0 (diet 1), 10 (diet 2), 25 (diet 3), and 35 (diets 4 and 5). Diet 5 was also supplemented with the amino acids lysine, arginine and threonine. The results showed a direct relationship between fish mortality and the increment of jack bean meal. In the second experiment, three methods were tested to extract the non-thermolabile toxins from jack beans using 25% canavalia seed protein as a partial substitute of the total protein in diets for tilapia. The results showed no significant differences in growth (weight gain, final weight) and food conversion rate between fish ingesting the diets containing the treated jack bean and the control diet ( P < 0.01). It is concluded that canavalia seed meal is potentially useful as a partial substitute for fish meal in tilapia diets. However, caution must be exercised when using this protein source because of the presence of residues of non-thermolabile toxins in the meal.