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Apparent digestibility coefficient (ADC) values for mechanically extracted meal derived from roquette (Eruca sativa) seeds were obtained. The digestibility of dry matter (DM), protein and energy was measured using an inert marker in the diets and by faeces collection using the dissection method. Soybean meal and roquette meal had similar ADC values for protein and energy. Roquette seed meal was thereafter evaluated as a protein source in diets (400-g crude protein, 120-g crude lipid and 18.00 MJ gross energy kg-1 DM) fed to African catfish, Clarias gariepinus, fingerlings (10.4±0.4 g) to apparent satiation twice daily for 70 days. The test diets contained roquette seed meal as replacement for soybean meal protein in a control diet, providing 20%, 40% or 60% of the total protein. Catfish mortality was low (

This study was undertaken to determine the replacement value of Cassia fistula seed meal (CFM) for soybean meal (SBM) in practical diets of Oreochromis niloticus fingerlings. Five practical diets (350 g kg−1 crude protein) containing 0 g kg−1 (control), 170 g kg−1 (diet II), 340 g kg−1 (diet III), 509 g kg−1 (diet IV) and 670 g kg−1 (diet V) substitution levels of CFM for SBM were formulated and fed to triplicate groups of O. niloticus fingerlings (mean initial weight of 10.22 ± 0.03 g) for 70 days. Fish mortality increased linearly with increase in inclusion levels of CFM in the diet. Growth and diet utilization efficiency were depressed in fish fed diets containing CFM at varying inclusion levels. Feed conversion ratio, specific growth rate and protein efficiency ratio of O. niloticus fed on diet containing 170 g kg−1 substitution level of CFM were similar (P > 0.05) to the control diet. Digestibility of the different diets decreased with increase in inclusion levels of CFM. Fish fed diet containing 670 g kg−1 CFM had significantly lower carcass protein. However, no significant differences were observed in carcass protein and lipid contents between fish fed the control diets and diet containing 170 g kg−1 CFM. The most efficient diet in terms of cost per unit weight gain of fish was obtained in 170 g kg−1 CFM dietary substitution.

Macadamia presscake, the by-product from oil extraction process of low-grade kernels of macadamia nuts, was evaluated as a dietary protein supplement for tilapia, Oreochromis niloticus (L.), reared in outdoor concrete cisterns. Five isoproteic diets (28% crude protein) were fed to tilapia for 100 days. The diets comprised a control, which contained full-fat soybean as the protein source, and four test diets in which the full-fat soybean meal was progressively substituted (10%, 20%, 50% or 100%) with macadamia presscake. Final weight, daily weight gain, specific growth rate and apparent protein digestibility were significantly different (P 0.05). Body protein deposition was not affected by the inclusion level of mac-adamia presscake in the diet. Results showed that macadamia presscake was suitable as a dietary protein supplement for tilapia when incorporated up to 50% replacement for soybean protein. The nutrient content of full-fat soybean meal is apparently similar to that of macadamia presscake but the quantity of macadamia presscake in fish feeds may be limited due to the less-than-optimal amino acid balance in macadamia presscake-protein.

Clarias isheriensis Sydenham fingerlings (60·42 ± 1·13g) were fed for 180 days with pelleted diets in which maize was progressively replaced with graded levels (0, 15,30,45%) of cocoa-pod husk meal (CPHM). There was a decline in growth rate with increase in dietary CPHM level, though this was not significantly different (P 0·05). Fish mortality was low (< 2%) in all dietary treatments tested. Lack of significant difference in growth performance and nutrient utilization indicated that CPHM could be incorporated into low-cost diets for C. isheriensis up to the 30% level. In a second experiment, three feeding regimes of 15% CPHM diet were tested with C. isheriensis fingerlings (60·81 ± 1·87g) over 180 days and results showed no significant (P > 0·05) differences among the feeding regimes tested, with regards to growth, feed conversion and fish yield. This suggests that the growth of C. isheriensis from fingerling to adult size (≥ 200g) can be satisfied in one single feeding equivalent to 3% body weight per day.