The suitability of different mixtures of soybean meal (SBM), cottonseed meal (CSM) and groundnut cake (GNC) as ingredients to replace fish meal in the diets of Nile tilapia (Oreochromis niloticus L.), was evaluated over a 56-day growth period. Nine isonitrogenous (320 g.kg-1), isolipidic (100 g.kg-1) and isoenergetic (18 KJ.g-1) test diets were formulated in which different mixture combinations of SBM, CSM and GNC proteins replaced fish meal (FM) protein at levels of 50% and 75%. The control diet had FM as the sole protein source. Fish were fed at 6-4% body weight per day. The growth experiment was conducted in plastic tanks in a recirculation system. Each dietary treatment was in triplicate. Growth performance and feed utilization of fish fed with the oilseed meal mixtures indicated that up to 50% replacement could be more effective than a single source for the substitution of fish meal in tilapia diets. This was particularly evident with the diet containing equal proportions of all oilseed meals (EQ50). Combination of oilseed meals in different proportions was more effective than the single individual sources. This could be due to a compensatory effect which led to some reduction of antinutritional factors coupled with improved essential amino acid profile in the diet as a result of mixing.

ABSTRACT:The nutritional suitability and cost effectiveness of cottonseed meal (CSM) as protein source in the diet of Nile tilapia (Oreochromis niloticus L.) with mean initial weight 4.24±0.20 g, was evaluated over a 56-day growth period. Four isonitrogenous (320 g kg -1 ), isolipidic (100 g kg -1 ) and isoenergetic (18 KJ g -1 ) test diets were formulated in which CSM protein replaced fish meal (FM) protein at levels of 0% (control), 25%, 50% and 75%. The control diet had FM as the sole protein source. The growth experiment was conducted in plastic tanks in a recirculation system each dietary treatment was in triplicate. After 56 days of feeding fish at 6% -4% body weight per day, CSM protein replacements of 25% and 50% did not significantly (P<0.05) affect growth (Specific Growth Rate, Weight Gain) and feed utilization (Feed Intake, Feed Conversion Ratio, Protein Efficiency Ratio, Apparent Net Protein Utilization and Energy Retention). However, the highest replacement level (75%) significantly reduced these parameters compared to the control diet and this was attributed to low levels of lysine, methionine and threonine and also to high levels of gossypol, trypsin inhibitors saponin and phytic acid in the diet. In terms of cost effectiveness, all the CSM based diets were more profitable than the control. The study indicated that CSM could replace at least 50% of fish meal protein in the diet of O. niloticus without adversely affecting growth and feed utilization and the most cost effective diet was also the diet with 50% inclusion level of CSM. @JASEM

An investigation into the food and feeding ecology of the cichlid, Sarotherodon galilaeus multifasciatus in a tropical meteoritic lake in Ghana was undertaken. Stomachs of the fishes, at two length classes, representing adults and juveniles, were examined and the food items identified. The juveniles of Sarotherodon galilaeus multifasciatus feed mainly on insect and insect larvae and relatively small quantities of diatoms but avoiding macrophytes. A striking feature in the composition of juvenile diet was the considerable quantities of ingested sand, which constituted about 16% of stomach contents. Ingested sand may be helpful in maceration of food in the pyloric stomach. A sandy substratum may, therefore, appear ecologically important for juveniles of the species. Adult stomachs contained mainly phytoplankton, chironomid and insect larvae with no ingested sand. No significant differences were found in the stomach contents of the fishes for the dry and wet seasons due, partly, to the lack of any considerable seasonal differences in allochthonous inputs into the lake waters. The fishes exploit a wide range of food resources in the open, sub-littoral and littoral zones of the lake. Further studies to include growth and recruitment are recommended to enhance future production of the species under culture conditions. @ JASEM

This study was conducted to determine the nutritional (proximate and energy) composition of selected shea nut by-products (SNPs) namely; shea nut meal (SNM, solvent extracted), shea nut cake (SNC, mechanically extracted) and shea nut cake (SNCW, water extracted) and their apparent digestibility coefficient (ADC) by Nile tilapia, Oreochromis niloticus. The ADC was determined using a reference diet with chromic oxide indicator and test diets that contained 70% reference diet and 30% of SNPs being evaluated. Nile tilapia (26.89 ± 3.19 g) was stocked in rearing tanks at 12 per tank and their faeces was collected from two replicate groups of fish by siphoning. Crude protein (CP), crude lipid (CL), crude fibre (CF) and gross energy (GE) of SNM,