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The replacement value of palm oil for codliver oil in diets for juvenile African catfish (initial weight 24.04 g) was investigated. For 8 weeks, fish were fed experimental diets in which there was either 9% codliver oil (Diet 1), 6% codliver oil, 3% palm oil (Diet 2), 3% codliver oil, 6% palm oil (Diet 3), or 9% palm oil (Diet 4).There were significant differences in body weight gain among all treatments, with fish fed diets 2 and 3 performing better. Fishes fed diets 3 and 4 had significantly higher survival than fish fed diets 1 and 2. Significant differences were recorded in carcass parameters of fish at the end of the feeding trial, with fish fed diets 3 and 4 having higher values. Fish fed diet 2 had higher blood parameters which decreased with increasing level of palm oil in the diet. There was no significant difference in the organoleptic properties of fish fed different dietary treatments and the end of the trial. The results of this study shows that diet with 3% codliver oil, 6% palm oil is nutritionally suitable for feeding the African catfish.

3 Abstract: The proximate composition, pasting characteristics, Water Absorption Capacities (WAC), Oil Absorption Capacities (OAC), bulk densities (packed and loosed), Least Gelation Concentrations (LGC) swelling capacity, solubility, and viscosity of fermented and unfermented maize-tilapia mixes namely -MUF , 1 MUF , MFF and MFF was investigated. WAC, OAC, PBD, LBD and LGC obtained are 271.7%; 176.0%; 2 3 4 0.570gmL ; 0.468g/ml; 10% (w/v) and 253.3-300%; 150.0-246.7%;0 355-0.468gmL ; 0. 513-0.610gmL ; 1 1 1 4.0-8.0% (w/v) respectively. Solubility and swelling power increased with increase in temperature. Viscosity increased with increase in the cold paste concentration and temperature. Peak viscosity of MF was 300RVA and 253.83-270.33 RVA in the formulated maize-tilapia mixes.

The effects of replacing high percentages (50%, 75% or 100%) of dietary protein from fish meal with soy protein concentrate on growth, diet utilization, and carcass composition of the African catfish, Clarias gariepinus, was evaluated. Supplemental methionine was added to the diet formulation in which soy protein concentrate replaced 100% of fish meal protein. Diets were formulated (420 g crude protein/kg and 17.5 kJ gross energy/g dry diet) and fed to catfish fingerlings (13.1±0.5 g) to apparent satiation twice daily for 70 days. Replacement of 50% and 75% of fish meal protein with soy protein concentrate did not affect growth, feed utilization or carcass composition, which were similar (P > 0.05) to those fed with the control diet. At 100% replacement, growth and feed utilization were depressed and slightly inferior hematological characteristics were observed, compared with the other treatments. Liver histology of catfish fed any of the diets showed no alternations. Results indicate that 75% of...

Artificial spawning was induced in female African giant catfish, Heterobranchus bidorsalis by single intramuscular hormone injections of carp pituitary suspensions (CPS) at 4 mg/kg body weight (bw), 1.5 ml of homoplastic pituitary suspension (HPS) per fish or human chorionic gonadotropin (HCG) at 2000 IU/kg bw, over 3 months of rainy season (June to August) in Nigeria. At ambient temperature (27±1 °C), ovulation occurred within 14–18 h post injection. Egg hydration gave 16–20% increase in egg diameter. Hatching rates were high (>84%) and similar for all hormone-treated fish (P>0.05). The percentage normal larvae hatched ranged from 81.6% to 86%. They were reared in 500-l circular tanks and fed initially on zooplankton, followed by brine shrimp nauplii and finally weaned onto commercial fish fry diet. During the larval rearing trials for 30 days, survival rates >82% were achieved. Although the four hormones tested were effective inducers, the use of HPS would save operational costs in fish hatchery management in African countries.

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.

Two aquatic plants: water fern, Azolla africana and duckweed, Spirodela polyrrhiza were evaluated as feedstuffs in production diets for Nile tilapia, Oreochromis niloticus fingerlings. Eleven diets (30% crude protein) containing fish meal protein substituted at a rate of 5, 10, 20, 30, and 100% for either of the plant ingredients were formulated. A diet without any of the plant ingredients served as the control. Nile tilapia fed diets containing duckweed showed superior growth performance. There were no significant differences (P > 0.05) in growth responses of fish fed either 10% duckweed and 5% water fern dietary inclusion or the control diet. There was a growth depression in fish with increased dietary inclusion of both plants. The most cost-efficient diet was obtained in a diet with 30% duckweed dietary inclusion. Results of this study indicated that duckweed and water fern could be substituted for fish meal protein up to 10% and 5%, respectively, in low-cost diets for Nile tilapia without com...

Stomach contents analyses of 330 specimens of the electric catfish, Malapterurus electricus (Gmelin 1789) (standard length, 10.1-30.5 cm) collected in Mahin Lagoon (southwestern Nigeria) established it as a bottom feeder. A preponderance of insects and prey fish, which accounted for 100% occurrence and > 18% of total volume in the stomachs of specimens, suggested a predatory habit. Carbohydrases (amylase, maltase), chitinase, proteases (pepsin, chymotrypsin, trypsin) and lipases were detected in different gut regions with different activity, which correlated with its predatory diet. KEY WORDS: digestive enzymes, stomach contents, food, electric catfish, Malapterurus electricus.

Analyses of stomach contents of (1093) Heterotis niloticus (Cuvier 1829) in the River Ogbese, Owena Reservoir and Mahin Lagoon (southwestern Nigeria) established it as a benthic feeder in the river and a planktonic feeder in the reservoir and lagoon. There was a preponderance of zooplankton, accounting for > 80% occurrence and > 25% of total volume in the stomachs of specimens from all habitats; this suggests a microphagous habit. Digestive enzyme assays in the different gut regions (oesophagus, stomach, pyloric caeca, ileum, rectum) of H. niloticus revealed an array of glycosidases (amylase, sucrase, maltase, lactase, cellulase); proteases (pepsin, trypsin, chymotrypsin) and lipases were also detected. The pattern of distribution and relative activity of the enzymes is consistent with its planktophagous diet. Haematocrit values, haemoglobin concentrations, erythrocyte and leucocyte counts, mean cell haemoglobin concentration, plasma protein, glucose and albumin, inorganic ion (sodium, chloride, calcium, ...

Mature winged bean ( Psophocarpus tetragonolobus ) (cultivar Tpt26) seeds were roasted or autoclaved and their meals evaluated as a dietary protein source for the African catfish. Five dry practical diets (400 g protein/kg and 17.5 kJ gross energy/g dry diet) containing menhaden fish meal or each of the heat-processed winged bean meals as partial replacement (80%), (with or without 5 g dl -methionine/kg diet supplementation) for menhaden fish meal, were prepared and fed to triplicate groups of catfish fingerlings (5.8±1.2 g) to satiation for 70 days. No mortality occurred throughout the study and satisfactory diet acceptance was observed when the heat-processed winged bean meals replaced menhaden fish meal. Differences were found in weight gain, specific growth rate, feed and protein efficiency ratios, but were not significant ( P >0.05). Digestibility of crude protein and gross energy content of the diets were high (>85%) and comparable to that of menhaden fish meal. Carcass composition of catfish did not vary significantly ( P >0.05) between diet treatments. Results indicate that both autoclaved and roasted winged bean meals were acceptable as protein sources and can replace 80% of menhaden fish meal in catfish diets.

Fish silage was prepared by fermentation of stunted tilapia with 50 ml/kg Lactobacillus plantarum starter culture and 150 g/kg sugar beet molasses at 30°C for 7 days, pasteurized, neutralized, and stored at 30°C for 180 days. Addition of 50 ml/kg onion extract proved effective as lipid antioxidant, with peroxide values lower than the control (P 0.05) among diets. Protein and lipid losses were low ( 80%) and similar (P>0.05) among diets. Moist fish silage pellets were physically stable and highly digestible to O. niloticus, and suitable as farm-made feeds for fish.

Raw heads of the river prawn, Macrobrachium vollenhovenii, were fermented with Lactobacillus plantarum at 30 °C using molasses or cassava starch as the carbohydrate source. After incubation for 7 days, a desirable and stable pH w w ) and solar-dried. The dried shrimp head silage meals were incorporated as protein supplements into pelleted semi-purified diets for catfish, Clarias gariepinus. Apparent digestibility coefficients of dry matter, crude protein, gross energy and essential amino acids in the silage by catfish fingerlings was high (> 70%). It was concluded that dried fermented fish silage is suitable and has a potential as a protein feedstuff in fish diets.

Induced breeding trials of two clariid catfishes, Clarias gariepinus and Heterobranchus bidorsalis, were conducted using five doses (2, 4, 6, 8 or 10 mg/kg) of acetone-dried tilapia pituitary (ADTP) extracts. Oocyte maturation and ovulation were induced in female catfishes by single intramuscular injection of 6–10 mgkg ADTP; optimum results were obtained with 8 mgkg in both catfishes. At ambient temperature (27 ± 1 C). ovulation occurred within 14–18 h post-injection resulting in 16–20% increase in egg diameter. Fertilization and hatching percentages increased (P < 0.05) with increases in hormone dosage. Survival of fry fed a mixed zooplankton diet was high (ranging from 79% to 85%) after 30 d of rearing.

Raw heads of the African river prawn (Macrobrachium vollenhovenii) were fermented with 5% ( w w ) Lactobacillus plantarum as inoculum at 30 °C using 15% ( w w ) cane molasses as a carbohydrate source. After incubation for 7 days, a desirable and stable pH, w w ) prior to fermentation restricted protein hydrolysis by inhibiting the activity of endogenous autolytic enzymes. Addition of onion extract at 5 ml kg−1 proved effective as an antioxidant as the thiobarbituric acid reactive substances value remained low after 30 days' fermentation. In a storage experiment, fermented shrimp heads were stored at 30 °C for 180 days and analyzed at intervals. The non-protein nitrogen increased and attained a maximum of 50.1% of total nitrogen content after 180 days. Proximate composition varied slightly during storage and there was a > 12% loss of tryptophan.

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.

Fish-silage (FS), prepared from lactic acid fermentation of whole tilapias, 5% sugar beet molasses and 2% Lactobacillus plantarum, was blended and co-dried with soybean meal (SBM), poultry by-product meal (PBM), hydrolysed feather meal (HFM) and meat and bone meal (MBM). The blends were evaluated as protein source (providing 50% of dietary protein) in dry diets (40% protein, 4·3 kcal g−1 gross energy) for juvenile catfish, Clarias gariepinus, fed at 4% body weight day−1 for 70 days. The fish-silage pellets maintained their shape during water immersion and their water stability was high and similar (P>0·05) to that of a reference diet. Clarias gariepinus fed on the different fish-silage diets showed some significant (P 0·05). Protein digestibility was reduced (P

Fermented fish silage was prepared from whole mixed-sex tilapia (Oreochromis niloticus), 15% molasses and 5% Lactobacillus plantarum starter culture and used as protein source in tilapia diets. Four alternative binders (carboxymethyl cellulose, corn starch, guar gum or wheat gluten) were incorporated in diets at 3% and their effects on water stability and nutrient leaching were determined. Water stability of the pellets showed that high physical stability of the pellets was maintained regardless of the binder used, and losses of total nitrogen were low (< 3%) on a per gram diet recovered basis. All-male O. niloticus fingerlings (mean weight, 48·9 g) were fed the appropriate diets at a rate of 5% of body weight per day, twice daily, for 30 days in a recirculated water system with water temperature maintained at 27°C. Apparent digestibility coefficients for dry matter, nitrogen or lipid in the diets were high and similar when carboxymethyl cellulose, corn starch or wheat gluten was used as the binder; but were reduced (P < 0·05) with guar gum.

Resume Fagbenro O., K. Jauncey, G. Haylor. Aquat. Living Resour., 1994, 7, 79-85. Dry diets containing varying levels of dried fermented fish silage and soybean meal blend (FS: SBM) as replacement for 25,50 or 75 % of fish meal protein were fed to juvenile Oreochromis niloticus (8.210.1 g) and Clarias gariepinus (10.8k0.3 g) at 5 % body weight per day for 70 days. Diets containing CO-dried FS: SBM supported weight gains and growth rates similar to those in the control treatment without significant differences @>0.05). Feed conversion, protein efficiency ratio and protein productive values followed a similar trend with growth performance values. Apparent protein digestibility decreased in both fish species with increasing dietary level of CO-dried FS: SBM. Carcass composition of experimental fish were not affected by the diets and morphological defects were not observed. Results indicate that CO-dried FS: SBM can partially replace fish meal protein as well as establish the potential of utilizing wastehndersized tilapias as a protein feedstuff in dry aquaculture diets.

Fermented fish-silage was prepared from whole tilapias, 15% molasses and 5% Lactobacillus plantarum starter culture and used as protein supplement in moist diets for juvenile catfish, Clarias gariepinus. Carboxymethyl cellulose, guar gum or wheat gluten was incorporated as alternative binder into diets at 2% and their effects on water stability and nutrient leaching were determined. The pellets maintained a high water stability regardless of the binder used, and losses of total nitrogen were low (

Fish silage was prepared from whole juvenile tilapia by fermentation with 50 g kg−1 (wet weight, w/w) Lactobacillus plantarum at 30°C using 150 g kg−1 (w/w) molasses, corn flour or tapioca flour as alternative fermentation (carbohydrate) substrates. After incubation for 7 days, a desirable and stable pH of less than 4.5 was attained and the source of fermentation substrate did not affect the soluble nitrogen content or the proximate composition of the liquid silage after 30 days storage. Soyabean meal, used as filler material, was blended with the liquid silage in ratios 1:1, 2:1, 3:1, 3:2 (w/w) and oven-dried. The various proportions of fish silage:soya-bean meal improved the dry matter (DM) and nutrient composition of the silage after drying. The 1:1 dried fish silage was incorporated into dry pelleted diets (650 g kg−1 diet) formulated for tilapia (Oreochromis niloticus). The pellets had a tough consistency and maintained their shape during water immersion. Water stability of dried fish silage pellets were similar (P>0.05) to that of a reference diet. Apparent digestibility coefficients for DM, protein and energy of the silage diet were 82.8%, 84.5% and 82.8%, respectively. It was concluded that co-dried fermented fish silage is suitable and has a potential as a protein feedstuff in fish diets.

Fermented fish silages were prepared from whole tilapia (Oreochromis niloticus), 15% molasses and 5% Lactobacillus plantarum starter culture. After fermentation for 72 h, potato extracts (PE), formalin or ginger extracts (GE) were added at 5 ml/kg silage as proteolytic inhibitor or lipid antioxidant, and incubated at 30°C for 30 days. The effects of presence or absence of these additives on various protein and lipid quality parameters were periodically examined. PE had a slight and insignificant effect on protein solubilization and proteolytic activity; hence it was not effective as a proteolytic inhibitor. Formalin prevented further hydrolysis of protein and reduced ammonia production. GE proved effective as an antioxidant in fermented tilapia silage, as the thiobarbituric acid value remained low after 30 days' incubation. The tilapia silages were incorporated into dry tilapia diets and the digestibility of nutrients determined. The formalin-treated tilapia silage diet gave significantly reduced (P < 0·5) digestibility of dry matter, nitrogen or lipid compared to the control, PE-treated or GE-treated silage diets.

Haematological profile of Heterobranchus bidorsalis (Geoffroy St. Hilaire 1809) was determined. Haematocrit values, haemoglobin concentrations, erythrocyte and leucocyte counts, mean cell haemoglobin concentration, sodium and potassium ions concentrations were 24.75±1.23%, 5.43±0.25 g/100 ml, 1.99±0.52 106/mm3 and 7.25±0.60 104/mm3, 22.11±0.77%, 802.52±36.97 and 83.54±5.05 mg/1, respectively. H. bidorsalis fingerlings were subjected to a range of salinities, 0, 3, 6, 9, 12 and 15 ppt. The optimum salinity range for survival and good growth performance was determined as 0–3 ppt. Survival was >85% from 0–9 ppt with no significant differences (P>0.05), but decreased progressively as salinity increased. Qualitative and quantitative assays of digestive enzymes in the different regions of H. bidorsalis guts revealed an array of carbohydrases, proteases and lipases. Enzyme activity was restricted to the stomach, duodenum and ileum with fewer enzymes recorded in the stomach. The pattern of distribution and relati...

Fermented fish silage was produced from minced tilapia ( Oreochromis niloticus ), 15% molasses and 5% Lactobacillus plantarum culture. Initially, batches of the fish silages were fermented at 5, 20, 30 or 35°C for 30 days. The pH declined rapidly at 20, 30 and 35°C but at 5°C, pH decline was slower. Protein solubilization (autolysis) in the fish silages was temperature-dependent as the non-protein nitrogen content (NPN) increased rapidly at higher temperatures. In a second experiment, fish silage was fermented at 30°C for 7 days after which autolysis was halted, then stored at 30°C for 180 days and analysed at intervals. The NPN attained a maximum of 51·4% of total nitrogen content after 180 days. Proximate composition of tilapia silages varied slightly during storage and there was a slight loss of tryptophan during fermentation and storage. The stored wet tilapia silages were blended with soybean meal (1:1, w/w) and dried. The nutritional value of co-dried tilapia silage as a dietary protein supplement for catfish ( Clarias gariepinus ) was studied in digestibility experiments. Although the protein quality of wet tilapia silage was reduced during storage, there were no differences ( P > 0·05) in the apparent protein digestibility coefficients of diets containing co-dried tilapia silages. It is suggested that autolysis in the stored tilapia silages had little effect on proten digestibility in the catfish.

Fermented fish silages were prepared from whole tilapia ( Oreochromis niloticus ), molasses and Lactobacillus plantarum starter culture. The effects of cooking and addition of 5% salt on the proximate composition, various protein and lipid quality parameters were measured over a 30-day period of incubation at 30°C. The silages were stable during fermentation and storage, and no appreciable loss of nutrient contents was noted. The changes observed were increased degree of autolysis and ammonia production. Addition of salt or cooking of substrate before fermentation prevented continued protein hydrolysis by inhibiting the activity of endogenous autolyzing enzymes and decreased the formation of total volatile bases. The apparent digestibility of dry matter, of nitrogen and of the energy content of silage-based diets for tilapia was higher in both the cooked and salted fish silages than in the raw fish silage.

Nigeria owns significant fisheries with a coastline of 853km and over 14 million hectares of inland waters. The contribution of fisheries to the Nigerian economy is significant. However, the industry is laden with various problems. The domestic fish production (0.61MT) has fallen short of the demand (1.55million MT). To achieve the much desired fish-food sufficiency, aquaculture development is the solution.

The dietary habits of the giant African clariid catfish, Heterobranchus bidorsalis (Geoffroy St. Hilaire 1809) inhabiting Owena Reservoir (Southwestern Nigeria) were investigated. Stomach content analyses established that it had an euryphagous diet. The diet comprised mainly plankton, insects, fish and detritus although, plant parts, benthic invertebrates and tadpoles were consumed. Detritus was very prominent accounting for between 68.1–74.5% occurrence and 13.9–19.6% volume in all sizes of fish examined, which indicated that it was a benthic feeder. There was a progression from planktivorous diet in fish below 12 cm standard length (SL) through a transitional insectivorous phase (SL, 12–27 cm) to a predominantly piscivorous diet in fish above 27 cm SL. It was capable of filter feeding only when young but later became predatory, consuming appropriately sized prey organisms as it grew older. No seasonal variation was established in food preference of any size of fish.

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.

Feeding and digestibility studies were conducted in concrete ponds to evaluate the use of coffee (Coffea robusta) pulp as partial and total replacements for yellow maize in low-cost diets for the catfish, Clarias isheriensis (Sydenham, 1980). The percentages of dietary coffee pulp inclusion were 0 (diet 1, control), 10 (diet 2), 20 (diet 3) and 30 (diet 4). All the diets were formulated to contain 37% crude protein using cheap, locally available feed ingredients, and fed daily to experimental fish in replicated dietary treatments at 2–10% of fish biomass for 150 days. Fish survival was high, consequent upon good water quality in all treatments. There were significant differences (P

Trials on growth performance, nutrient utilization and digestibility, as well as carcass composition, were conducted on the clariid catfish, Clarias isheriensis (Sydenham, 1980) to evaluate the replacement value of peels of cassava, yam and plantain, and maize chaff, as substitutes for maize in low-cost fish diets. Triplicate groups of C. isheriensi fingerlings (mean weight, 34·72 g) were fed for 84 days with 37% crude-protein diets containing each of the energy substitutes at 25% inclusion level. The maize chaff diet produced the greatest body weight increases and best growth performance as well as the best feed utilization. This was followed by yam peel, plantain peel and cassava peel diets in decreasing order. Apparent nutrient digestibility coefficients of the experimental diets followed a similar trend. Only the maize chaff diet compared favourably with the control (yellow maize) diet with regard to nutrient utilization and digestibility, which indicated that maize chaff had the greatest potential and desirability as a replacement for yellow maize as the energy source in low-cost diets for C. isheriensis.

Digestive enzyme assays in the different gut regions (oesophagus, stomach, caecum, duodenum, ileum, and rectum) of three commercial African freshwater fish species: Nile tilapia Oreochromis niloticus, African snakehead fish Parachanna obscura, and African long knife fish, Gymnarchus niloticus, revealed an array of glycosidases (amylase, sucrase, maltase, lactase, and cellulase); proteases (chymotrypsin, pepsin, and trypsin) and lipases. The pattern of distribution and relative activity of the enzymes showed that the fishes are capable of digesting carbohydrates, proteins and lipids such that they complemented the different dietary habits of the three fish species. Enzyme activity was not detected in the oesophagus and rectum of the three fish species. The relative distribution and activity of the various enzymes were possibly induced by the nutritional requirements of the fishes.

Reference values for some haematological indices of Parachanna obscura, Malapterurus electricus and Malapterurus minjiriya were determined. The mean ± SD values for erythrocyte count (Ec), leucocyte count (Lc), haematocrit (Hct), haemoglobin concentration (Hbc), erythrocyte sedimentation rate (ESR), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), and plasma protein content (g/dl) determined for P. obscura were 2.00 ± 0.71 x 10 12 /litre, 40.10 ± 1.32 x 10 9 /litre, 26.40 ± 3.89 %, 11.48 ± 1.55 g/dl, 13.12 ± 1.26 mm/h, 131.70 ± 108.20 fl, 57.28 ± 43.25 pg, 43.48 ± 6.97 g/dl, 62.90 ± 9.70 g/dl respectively. Ec, Lc, Hct, Hbc, ESR, MCV, MCH, MCHC and plasma protein content determined for M. electricus were 1.96 ± 0.17 x 10 12 /litre, 31.87 ± 2.30 x 10 9 /litre, 32.03 ± 1.94 %, 7.08 ± 0.22 g/dl, 2.56 ± 0.53 mm/h, 158.59 ± 5.16 fl, 35.24 ± 1.79 pg, 0.225 ± 0.018 g/dl and 52.89 ± 7.23 g/dl, respectively. Ec, Lc, Hct, Hbc, ESR, MCV, MCH, MCHC and plasma protein content determined for M. minjiriya were 2.09 ± 0.21 x 10 12 /litre, 38.48 ± 3.10 x 10 9 /litre, 34.04 ± 2.15 %, 8.28 ± 0.25 g/dl, 2.71 ± 0.58 mm/h, 168.15 ± 8.01 fl, 36.43 ± 2.17 pg, 0.255 ± 0.027 g/dl and 50.85 ± 9.86 g/dl, respectively.

A feeding study was conducted to assess the value of Tamarind, Tamarindus indica seed meal as dietary carbohydrate in the diets of Nile Tilapia, Oreochromis niloticus . Tamarind seeds were used to replace maize at 0, 20, 40, 60, 80, 100 % substitution levels for treatments 1 to 6. Growth trial was conducted in outdoor concrete tanks for 56 days. The fishes were fed at 4 % body weight twice daiy. There were no significant variations in the mean weight gain, specific growth rate (SGR), food conversion ratio (FCR) and protein efficiency ratio (PER) (p >0.05). The apparent digestibility coefficient (ADC) of protein and energy of the fishes fed diets 1 – 6 were similar (p > 0.05). There were nosignificant differences in the bood total erythrocyte counts, (TEC), pack cell volume (PCV) and red bood cells count (RBC) (p >0.05). Based on the findings, complete replacement of maize with tamarind seed meal in the diets of O. nilotcus is recommended. Keywords : Tamarind, Replacement, Maize, Oreochromis niloticus Animal Research International Vol. 1 (3) 2004 pp. 164-168

Defatted cocoa cake, a by-product of the cocoa fermentation process, was evaluated as a direct feed in the monosex culture of Tilapia guineensis (Dumeril) stocked at 10 000/ha in 160-m 2 earthen ponds. Experimental yield trials were compared with two types of controls: a locally manufactured fish diet and an unmanaged system. A completely random design was used with three treatments replicated three times and lasting 120 days. Survival of the fish ranged from 90.21 to 93.13%. At harvest, average net yields were 2310.00, 1707.50 and 1133.13 kg/ha from the fish diet treatment, cocoa cake treatment and unmanaged system, respectively. Feed conversion values (based on dry matter inputs) averaged 5.12 and 2.30 for the fish fed the cocoa cake and fish diet, respectively. Analysis of the stomach contents of fish from the experimental pond showed that cocoa cake was utilized directly as feed.