Exogenous xylanase improves growth,protein digestibility and digestive enzymes activities in Nile tilapia,Oreochromis niloticus,fed different ratios of fish meal to sunflower meal

A 3 × 2 factorial experiment was designed to evaluate the effect of different ratios of fish meal (FM): sunflower meal (SFM) with or without exogenous xylanase supplementation on growth, feed utilization, digestive enzymes activities, apparent digestibility, intestinal and liver morphology and chemical composition of Nile tilapia, Oreochromis niloticus. Three isonitrogenous (329.80 g/kg of crude protein) and isoenergetic (18.46 MJ/kg gross energy) experimental diets were formulated as SFM₁ (FM:SFM = 2:1), SFM₂ (FM:SFM = 1:1) and SFM₃ (FM:SFM = 1:2) based on protein content. Each diet was supplemented with 0 or 0.5 g/kg of exogenous xylanase and was fed to triplicate groups of twelve fish (with initial weight, 1.31 ± 0.02 g) for 84 days. After 84 days of feeding period, the highest weight gain, specific growth rate, protein efficiency, protein productive value and the best feed conversion ratio were recorded in fish fed either SFM₁ or SFM₂ supplemented with exogenous xylanase. Whereas lowest growth performance was recorded in fish fed SFM₂ and SFM₃ un‐supplemented with xylanase. The highest activities of chymotrypsin, trypsin, lipase, amylase, alkaline phosphatase and cholecystokinin were observed in fish fed SFM₁ and SFM₂ diets supplemented with xylanase. The highest ADCs of dry matter, protein, lipid and digestible energy were recorded in fish fed SFM₁ and SFM₂ diets supplemented with exogenous xylanase. Supplementation of exogenous xylanase improved muscularis mucosa thickness, height of mucosal folds and enterocytes of intestinal fish. Addition of exogenous xylanase increased the calcium and phosphorus retention. Results of this study indicated that the addition of exogenous xylanase to diet containing high inclusion level of sunflower meal improved growth, digestive enzymes, nutrient digestibility, histological morphometric of liver and intestine and nutrient retention.     

Digestibility and feeding value of some feed ingredients fed to tilapia Oreochromis niloticus (L.)

The apparent digestibility of protein, organic matter and energy of high‐fibre and fibre‐reduced sunflower cakes, Kenya's ‘omena’ fishmeal, anchovy fishmeal and wheat bran were investigated in tilapia Oreochromis niloticus (L.) fingerlings. The feeding values and protein qualities of the above ingredients were also determined at two dietary protein levels. Fourteen diets were formulated, and each was provided to three tanks containing 12 fish in Expt 1 (digestibility study) and 25 fish in Expt 2 (feeding trial). Water temperatures and dissolved oxygen concentrations were maintained above 26 °C and 5.5 mg L^?1 respectively. Anchovy and ‘omena’ fishmeals each had an apparent digestibility coefficient for protein (ADC‐P) of 90%, whereas the fibre‐reduced and high‐fibre sunflower cakes had ADC‐P values of 89% and 86%. Wheat bran had an ADC‐P value of 75%, which was significantly lower than those found for the other test ingredients. Apparent digestibility coefficients for energy (ADC‐E) and digestible energy values (DE) were 86% and 78% and 4003 kcal kg^?1 and 3624 kcal kg^?1 for anchovy and omena fishmeals respectively. The corresponding values for the plant protein sources were 42% and 30% and 2200 kcal kg^?1 and 1400 kcal kg^?1 for the fibre‐reduced and high‐fibre sunflower cakes respectively. Diets based on the fibre‐reduced cake had higher levels of all amino acids than those based on the high‐fibre cake. Fish fed diets with 30% protein gained 40 g and had a feed conversion ratio (FCR) of 1.87, whereas those fed diets with 20% protein gained 35 g and had a FCR of 2.2. The source of protein had a significant effect on weight gain.     

Dry whey meal as a protein source in practical diets for Nile tilapia,Oreochromis niloticus fingerlings

ABSTRACT

This study was conducted as a trial of using dry whey meal (DWM) as a substitute for fish meal (FM) in practical diets for Nile tilapia, Oreochromis niloticus. Triplicate fish groups were fed on five isonitrogenous (30.2%) and isolipidic (6.9%) diets. The control diet (D1) used FM as the sole protein source. In the other four diets (D2–D5), FM protein was substituted by 25, 50, 75, or 100% DWM. Fish (3.5 ± 0.1 g) were stocked at a rate of 20 fish per 100-L aquarium and fed one of the tested diets up to satiation twice daily for 12 weeks. Fish growth, feed utilization, protein efficiency ratio, apparent protein utilization, and energy utilization for fish fed DWM diets up to 75% FM (D2–D4) tended to be higher but were not statistically different than the control diet. No significant effect of diet was found in whole-body moisture, crude protein, and total ash contents. Whole-body lipid content in fish fed the 100% DWM (D5) diet was significantly higher than that for fish fed the control diet. The optimal replacement level of FM by DWM was estimated by second-order polynomial regression to be 62.5%.     

Replacement of fish meal with a mixture of different plant protein sources in juvenile Nile tilapia, Oreochromis niloticus (L.) diets

A plant protein mixture (PPM) was tested to replace fish meal (FM) in diets for juvenile Nile tilapia, Oreochromis niloticus. Fish averaging (±SD) 3.7±0.14 g were divided into 15 groups. Three groups were fed each of five isonitrogenous (33.6%) and isocaloric (4.7 kcal g^?1) diets replacing 0%, 25%, 50%, 75% and 100% of the FM protein with similar percentages of PPM (PPM0, PPM25, PPM50, PPM75 or PPM100 respectively). The PPM consisted of 25% soybean meal, 25% cottonseed meal, 25% sunflower meal and 25% linseed meal, and 0.5% of both methionine and lysine were added to each diet except for the control. After 16 weeks of feeding, the fish fed diets PPM75 and PPM100 exhibited growth performance not differing significantly from the fish fed control diet. PPM substitution of up to 75% of the FM protein did not result in differences in the apparent protein digestibility compared with the control, whereas in the PPM100 group digestibility was significantly lower than in the other groups, except for fish fed the PPM75 diet. The incorporation of PPM in diets did not significantly affect whole‐body dry matter, protein, fat or energy compared with the control. The cost–benefit analyses of the test diets indicated that the PPM diets were economically superior to FM. The protein from PPM can completely replace the FM protein in the diets for Nile tilapia, based on the results of this study.     

Use of cottonseed meal supplemented with iron for detoxification of gossypol as a total replacement of fish meal in Nile tilapia, Oreochromis niloticus (L.) diets

The objective of this study was to determine the effect of total replacement of fish meal by cottonseed meal (CSM) supplemented with various levels of iron in practical diets on growth performance, feed utilization, body composition and some biological and haematological parameters of Nile tilapia, Oreochromis niloticus (L.). Juvenile fish (average weight 3.78±0.1 g) were stocked in 18 glass aquariums (80 L each) at 25 fish per aquarium. Fish meal (50% of the diet) was used as the sole source of animal protein in the control diet 1. Diets 2–6 had 100% CSM (0.145% free gossypol) protein with various levels of supplemented iron (86, 486, 972, 1458 and 1944 mg Fe kg diet^?1) in diets 2–6 respectively. Diets were fed to fish twice daily at a rate of 3% of body weight during the first 12 weeks then 2% of the total fish biomass daily until the end of the experiment (30 weeks). The results of this study revealed that, groups of fish fed diets 1, 4, 5 and 6 had significantly (P≤0.01) the higher average body weight and specific growth rate than those of fish fed diet 2 (100% CSM without iron supplementation) and diet 3 (100% CSM plus 486 mg Fe kg diet^?1). The best values for feed conversion ratio, protein efficiency ratio and condition factor (K) were recorded with groups of fish fed diet 4 (100% CSM plus 972 mg Fe kg diet^?1). Red blood cell count, haematocrit and haemoglobin were increased with increasing levels of iron and significantly affected by dietary iron. Hepatosomatic index for diets 3–6 were not significantly different (P>0.05) and superior to that of diet 1 control [100% fish meal (FM)]. The gonadosomatic index of males of Nile tilapia was not influenced by CSM diets with or without iron, while females of Nile tilapia were significantly influenced with iron and the lowest values were recorded with groups of fish fed diet 2 (100% CSM without iron supplementation). Apparent digestibility coefficients of protein, fat dry matter and energy were relatively high for most diets supplemented with iron and increased by increasing iron supplementation. There were no significant differences between groups of fish fed diet 1 (100% FM) and diets 5 and 6 which contained 100% CSM with additional 1458 and 1944 mg Fe kg diet supplemental iron^?1 respectively. Proximate composition of whole body was not influenced by diet. Adding 972 mg Fe kg diet^?1 from ferrous sulphate to the CSM‐based diets that contained 972 mg free gossypol (1:1 iron to free gossypol ratio) for Nile tilapia reduce the negative effects of gossypol and improved growth performance, feed utilization and blood parameters and can totally replace fish meal in tilapia diets.     

Effects of cellulase addition to canola meal in tilapia (Oreochromis niloticus L.) diets

The effects of commercial cellulase enzyme products on the nutritive value of canola meal (CM) were determined in tilapia fry. Nine diets were prepared by adding cellulase enzyme (1–5 g kg^?1) to control diet (containing no canola), low canola (41.7 g kg^?1 CM) and high canola (208.3 g kg^?1 CM). Tilapia fry was fed for 90 days, and growth, feed conversion ratio (FCR), body composition and nutrient digestibility were determined. Fish fed the diets containing the lowest levels of canola meal (41.7 g kg^?1) had similar final weight and FCR relative to the group fed the control diet, and high canola diet showed significantly lower growth than other groups (P < 0.05), irrespective of cellulase enzyme. The addition of canola meal to tilapia diets resulted in lower protein digestibility and cellulose digestibility. There were no significant differences in body compositions in all treatments. Addition of enzymes to canola meal diets had no significant effects on growth performance, body compositions and nutrient digestibility. The results of this study indicate that use in higher level of canola meal in tilapia diet was adversely affected growth parameters and FCR. Adding dietary cellulase enzyme in different rations to diets showed no significant differences in growth parameter.     

Partial replacement of soybean meal by sesame meal in diets of juvenile Nile tilapia,Oreochromis niloticus L.

An 8‐week feeding trial was conducted to determine the effects of replacing of soybean meal (SBM) with sesame meal (SM) in the diets of Oreochromis niloticus fingerlings. Seven practical diets (33 g kg^?1 crude protein, 19.2 MJ kg^?1 dry diet) containing substitution levels of 0%, 8%, 16%, 24%, 32%, 40% and 48% SM for SBM protein were formulated and fed to triplicate groups of O. niloticus fingerlings (mean initial weight of 8.74 ± 0.12 g). The fish survival rate, hepatosomatic index, viscerosomatic index and condition factor were not significantly affected by the contents of SM in the diets (P>0.05). The final body weight, weight gain (WG), specific growth ratio, feed conversion ratio and protein efficiency ratio of the fish fed the diet containing 16% SM were similar (P>0.05) to that of the fish fed the control diet. Except lipid, digestible contents of dry matter, crude protein, ash, gross energy and individual amino acids decreased while phosphorous increased with increasing SM levels. No significant differences were observed in whole‐body dry matter, ash and lipid contents among all the treatments (P>0.05); crude protein contents between fish fed the control diet and a diet containing 24% SM were also not affected significantly (P>0.05), and the phosphorus content was not significantly different when the SM level was increased to 32% (P>0.05). No significant negative differences were observed in the liver composition between fish fed the control diet and the diet containing 24% SM. The most efficient diet in terms of cost per unit WG of fish was obtained in 8% SM dietary substitution, while no significant differences were found among the 0%, 8% and 16% levels. It was indicated that SM can be utilized in the juvenile Nile tilapia diet to replace about 16% of SBM protein without causing negative effects on growth performance, body composition, liver composition and feed utilization.     

Evaluation of hydrolysed rubber seed meal as a dietary protein source for Nile tilapia Oreochromis niloticus L.

This study evaluated the use of hydrolysed rubber seed meal as a locally grown alternative feed ingredient to reduce the use of fishmeal within formulated feeds for tilapia. Five experimental diets were prepared by formulating different inclusion levels of hydrolysed rubber seed meal (0%, 25%, 50%, 75% and 100% of plant‐based protein contribution). Dried and defatted rubber seed meal was hydrolysed by adding rumen digesta liquid to the ingredient. For digestibility measurement, chromic oxide was added to each diet as an inert marker. The digestibility trial was conducted over a 14‐day period by collecting faecal matter from the rearing tanks. In addition, a growth trial was conducted over a period of 50 days using four replicates per dietary treatment. In both experiments, all fish were fed three times daily to apparent satiation. At the end of growth trial, the inclusion level of hydrolysed rubber seed meal up to 50% of plant‐based protein contribution did not give any significant difference compared to the control diet in terms of feed efficiency, specific growth rate and protein retention parameters. In the digestibility study, fish fed diets containing hydrolysed rubber seed meal up to a 50% of plant‐based protein inclusion level did not give any significant difference compared to the control diet in terms of protein and dry matter apparent digestibility. Based on the result of this growth and digestibility study, up to a 50% of plant‐based protein contribution of hydrolysed rubber seed meal can be used within formulated tilapia feeds without any adverse effect.     

Replacement of soybean (Glycine max (L.) Merrill) meal by lupin (Lupinus angustifolius) seed meal in diet for juvenile tilapia (Oreochromis niloticus×O. aureus) reared indoors

An 8‐week trial was conducted to assess the feasibility of replacing soybean meal (SBM) by lupin seed meal (LSM) in simulated commercial diets for juvenile tilapia starting at 0.3 g. Of the dietary protein (26% crude protein), 3.45% was from fishmeal and the rest came from the vegetable protein sources. The protein source of the control (C) diet came mainly from SBM and none (0%) from LSM. For the other diets, 33%, 67%, or 100% of the SBM protein was replaced by protein from either whole or dehulled LSM. One further diet was used: AW100, where alkaloid of the whole lupin seed was reduced. Survival, growth, and feed performance were compared among seven orthogonal contrasts to determine the effects of replacing SBM with whole LSM or dehulled LSM, and of reducing the alkaloid content. No differences in survival were found among all contrasts. No differences in fish growth and feed performance were found between feeding diet C and the other six diets ((whole, dehulled) × (33, 67, and 100)). Dehulled LSM diets resulted in better growth and feed performance than the whole LSM diets. Partial replacement of SBM by either dehulled LSM or whole LSM in diets obtained better growth and feed performance than total replacement. The AW100 diet resulted in equal fish growth but better feed performance than the W100 diet. This study concluded that partial, but not total, replacement of soybean protein with lupin seed protein in juvenile tilapia diets resulted in better, or at least equal, growth and feed performance. Dehulling further enhanced the growth and performance of LSM. Alkaloid removal improved feed performance but not the growth.     

Nutritional value of animal by-product meal in practical diets for Nile tilapia Oreochromis niloticus (L.) fry

Animal by-product meals (ABM) were substituted for fish meal in five experimental diets for Nile tilapia fry, Oreochromis niloticus (L), with 25%, 50%, 75% and 100% substitution. Two diets with 100% ABM were tested, one with 50:50 animal lipid:soybean oil, and the other with 100% fish oil as attractant. In general, the best growth and feeding performance was obtained with a control diet based on fish meal as the sole protein, but the results were not statistically different from those obtained with 75% and 100% ABM with soybean oil. A simple cost analysis suggested better economic efficiency when tilapia were fed with 100% ABM. It was concluded that animal by-product meal can be used as a sole protein source in commercial diets for Nile tilapia fry, without affecting growth and food utilization of the fish, improving the economics of feeding in comparison with fish meal.     

Effects of substituting fish meal with Azolla pinnata in practical diets for fingerling and adult Nile tilapia, Oreochromis niloticus (L.)

Abstract. Dry and fresh Azolla pinnata were evaluated as feed ingredients for fingerling and adult Nile tilapia, Oreochromis niloticus (L.). Dry Azolla was incorporated into practical diets containing approximately 30% crude protein and 360–400kcal/lOOg of GE lo replace 25,50,75 and 100% of the fish meal (FM) protein in the control diet. Fresh Azolla was also tested as a total diet for these fish. Formulated diets were fed to duplicate groups of fingerling (2–54g ± 0093) and adult (4033g ± 103) fish at a daily rate of 5% and 3% of their body weight respectively for 10 weeks. Growth and feed utilization efficiency of fish fed the control diet were significantly higher than of those fed Azolla-supplemented diets. Fish performance continued to deteriorate with increasing dietary Azolla level in the diets. This reduction was extremely sharp when dry and fresh Azolla were used as total diets. Furthermore, adult tilapia fed fresh Azolla started losing weight from the 7th week. Fish fed fresh Azolla had significantly higher moisture content than those fed formulated diets. Body protein and lipid contents were negatively correlated with Azolla levels in the diets, while body ash content showed a positive correlation. Results of this study indicate that young Nile tilapia utilizes Azolla more efficiently than the adults.     

Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry

Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.     

Substitution of fish meal with raw or treated cowpea (Vigna unguiculata L Walp,IT86‐D719) meal in diets for Nile tilapia (Oreochromis niloticus L.) fry

Two feeding experiments were carried out to evaluate the effect of partial substitution of fish meal (FM) with raw or heat‐treated cowpea Vigna unguiculata L. Walp var. IT86‐D719 seeds on growth performance, digestibility and pancreas tissue in Nile tilapia (Oreochromis niloticus L.) fry. Experiment 1 involved six isonitrogenous and isocaloric diets: four containing different concentrations of raw, whole cowpea meal (protein basis), a positive control with FM as sole protein source and a negative with cowpea meal as sole protein source. Substitution at up to 200 g kg^?1 had no significant effect on production parameters, although growth was negatively affected in the negative control because of seed antinutritional factor content. Experiment 2 evaluated the effect of heat treatment (oven drying at 48 °C; hot air drying at 70 °C; or autoclaving at 119 °C) and/or seed dehulling using diets containing 200 g kg^?1 cowpea meal presoaked in water. Only autoclaving eliminated trypsin inhibitor and lectin contents, independent of dehulling. Histological analysis indicated no histological changes in pancreas tissue. Raw or treated cowpea meal can replace FM in tilapia fingerling diets at up to 200 g kg^?1 protein content without significantly affecting productive parameters or pancreas tissue.     

Evaluation of replacing fish meal with corn protein concentrate in Nile tilapia Oreochromis niloticus fingerlings commercial diet

Four isocaloric‐isonitrogenous diets containing 0, 50, 100 and 190 g/kg corn protein concentrate (CPC) as replacement for dietary fish meal were fed to Nile tilapia Oreochromis niloticus fingerlings for 8 weeks. Tilapia growth parameters were not significantly (p > .05) different in fish fed diets with 0, 50 and 100 g/kg CPC and found to be superior compared to those fed on 190 g/kg CPC. Fish dressing ratios and body composition were similar among all treatments. The electron microscope indicated that the stomach size of control fish was slightly smaller and the wall was thinner while the stomach of the fish fed all other levels of CPC undergone a remarkable size increase and their walls were thicker after feeding diets with CPC. Total aerobic bacterial and coliform counts were significantly decreased in fish intestine when fed diets with 100 and 190 g/kg CPC compared with fish fed diets with 0 g/kg or 50 g/kg CPC. This study indicates that it is possible to replace up to 534 g/kg of dietary fish meal in tilapia fingerlings using 100 g/kg of CPC without any negative effect on fish growth and proximate body composition.     

Partial replacement of fishmeal with sunflower cake and corn oil in diets for tilapia Oreochromis niloticus (Linn): effect on whole body fatty acids

The objective of this study was to determine the effect of replacing fishmeal with high‐fibre and low‐fibre sunflower cakes (HFSC and LFSC) on whole body fatty acid composition in tilapia Oreochromis niloticus (Linn). Sex‐reversed O. niloticus males with an initial weight of approximately 16g ± 0.95 (SD) were used. A control diet based on herring meal and soybean meal was formulated. Six test diets were formulated such that low‐fibre (LF) and high‐fibre (HF) sunflower cakes (SC) contributed 30%, 60% and 80% of the dietary protein, and the diets were designated as LFSC‐30, LFSC‐60, LFSC‐80, HFSC‐30, HFSC‐60, and HFSC‐80 respectively. All fish were held at 25–28°C. They were fed three times daily their prescribed experimental diets for 70 days. At the end of this period they were starved for 24 h and weighed. Five fish representing the average weight of each replicated group (n=3) were frozen in plastic bags at –22°C for determination of fatty acid composition. Fatty acids in the fish were significantly influenced by diet. Palmitic, oleic and linoleic acids were the most abundant fatty acids in both the diets and the fish. Linoleic acid (18:2 ω6) was the most abundant fatty acid in diets based on sunflower cake. The levels of this fatty acid were also higher in fish fed diets with high contents of the sunflower cakes (LFSC‐60, LFSC‐80 and HFSC‐80) (31.3%, 34.7% and 29.7% respectively) than fish fed the control diet (13.8%). Percentages of long chain polyunsaturated acids of the ω‐3 family viz., docosahexaenoic (22:6 ω3) and eicosapentaenoic (20:5 ω3) were low in the diets and in the fish bodies. Fish fed the control diet had a higher level of 22:6 ω3 than those fed the other diets. The possible implications of the preceding findings for human health will be discussed.     

Growth performance,digestibility, and blood biochemical parameters of Nile tilapia (Oreochromis niloticus) reared in floating cages and fed poultry by-product meal

ABSTRACT

A 120-day feeding trial was conducted in floating cages to evaluate growth performance and digestibility of Nile tilapia (Oreochromis niloticus) juveniles fed diets containing different levels of poultry by-product meal (PBM) as a replacement for fishmeal. Nile Tilapia with an average body weight of 56.6 ± 0.28 g were used in this experiment. Five diets were formulated to contain graded levels of PBM at 0%, 5%, 10%, 20%, and 30% poultry by-product meal (PBM) and are referred as PBM0, PBM5, PBM10, PBM20, and PBM30, respectively. Groups of 25 Nile tilapia were fed close to the apparent satiation, three times a day. The results showed that growth performance, survival and whole-body composition for fish fed the experimental diets were not significantly different (P > .05) than fish fed the control diet. Apparent digestibility of dry matter, protein, lipid and amino acids of fish fed the PBM20 and PBM30 were lower compared to the other treatments (P < .05). The PBM dietary levels significantly lowered total protein, high-density-lipoprotein (HDL) and cholesterol concentration. The results of this study indicated that good quality PBM can be used up to 30% in commercial diets for Nile tilapia without any adverse effect.     

Nutritional evaluation of waste date fruit as partial substitute for soybean meal in practical diets of juvenile Nile tilapia, Oreochromis niloticus L.

The potential of waste date meal (WDM; low-quality date palm, Phoenix dactylifera L.) as a carbohydrate source in formulated diets for Nile tilapia was evaluated. Four isocaloric-practical diets (15.7 kJ g⁻¹) were formulated incorporating WDM at 0, 100, 200 and 300 g kg⁻¹ levels as partial substitutes for soybean meal (SBM). These were designated D₀ [284 g crude protein (CP) and 383 g carbohydrate (CHO) kg⁻¹ diet], D₁ (279 g CP and 446 g CHO kg⁻¹ diet), D₂ (207 g CP and 495 g CHO kg⁻¹ diet) and D₃ (175 g CP and 578 g CHO kg⁻¹ diet). Each diet was fed to three replicate groups of 30 fish [20.20 ± 0.09 g (±SE)] for 75 days. No feed-related mortality was observed during the entire experimental period. Final body weight (FBW) and specific growth rate (SGR) in the different treatments were statistically not significantly different ( P  > 0.05). Protein efficiency rate (PER) was lowest in diet D₀ and increased with decrease of SBM content (D₁–D₃). A significant increase in whole body lipid content was recorded in fish fed diets D₂ and D₃. Results showed that WDM could be a substitute for SBM up to 300 g kg⁻¹ in practical Nile tilapia diets without compromising growth.     

Potential of the use of peanut (Arachis hypogaea) leaf meal as a partial replacement for fish meal in diets for Nile tilapia (Oreochromis niloticus L.)

The rapid growth of tilapia culture has stimulated the expansion of tilapia feed production and a search for novel protein sources to replace fish meal. Vegetable or plant sources are promising alternatives and legumes are both naturally abundant and high in protein content. A study was carried out to evaluate the effects of replacing the protein from fish meal with peanut ( Arachis hypogaea ) leaf meal (PLM) in diets for male tilapia ( Oreochromis niloticus , initial body weight 75.3 g). Four isonitrogenous (35% CP) and isocaloric (18.834 kJ g⁻¹) diets were prepared to include 0% (CON), 10% (PLM10), 20% (PLM20) and 30% (PLM30) of PLM protein. Average fish weights at the end of the 126-day experiment were not statistically different among the fish fed CON, PLM10 and PLM20 diets. The PLM30 diet produced the poorest growth performance. Organic matter and protein contents of fish were similar in the CON, PLM10 and PLM20 diets. Carcass chemical composition showed a decrease in body fat content as PLM replacement levels increased. The high survival ratio in all dietary groups (>97%) suggests that PLM can be used in O. niloticus feeds for long periods without affecting fish growth performance or health.     

Effects of partial and complete replacement of freshwater shrimp meal (Caridinea niloticus Roux) with a mixture of plant protein sources on growth performance of Nile tilapia (Oreochromis niloticus L.) in fertilized ponds

Despite the well‐documented herbivorous food habits, commercial feeds for production of Oreochromis niloticus usually contain between 7% and 15% animal protein. However, animal protein feedstuffs are expensive, hence the need to search for cost‐effective alternatives in plant‐protein sources. Such alternatives are probably more effective in semi‐intensive systems where natural pond food forms part of the diet. This study evaluated the performance of O. niloticus after feeding diets in which fresh shrimp meal (SM) was gradually replaced by a mixture of plant‐protein sources in fertilized ponds. Three isonitronegenous (24% crude protein) diets containing 12 (control), 6% and 0% SM were fed to three groups of O. niloticus in four replicates per group for 250 days. Fish were fed daily at 2% body weight and sampled monthly to monitor growth and make feed adjustments. Growth, yields, survival and feed conversion ratio were not significantly different (P>0.05) among treatments. Growth of males was double that of females, while the sex ratio was skewed towards females. Although complete substitution of SM by plant protein did not affect the growth of tilapia, production cost was reduced by 36%. In conclusion, animal protein is not required in diets for production of O. niloticus in fertilized ponds.