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Development of Economically Feasible Feeds for Semi-Intensive Culture of
Tilapia, Oreochromis niloticus,
Using Locally Available Agricultural By-Products
Feeds and Fertilizers Research 4 (10FFR4)/Experiment/Kenya
Kenya Fisheries Department, Kenya
Moi University, Kenya
David M. Liti
1) Formulate cheap practical diets using locally available agricultural by-products for semi- intensive culture of Oreochromis niloticus.
2) Evaluate, under a semi-intensive culture system, the growth performance of O. niloticus fed these formulations as compared with that of fish fed maize and starter/broiler diet.
3) Determine the economic feasibility of using these diets as supplement to natural food in a semi-intensive O. niloticus production system.
4) Train young undergraduate and post-graduate fellows research skills in aquacultures, feed formulation and processing, and feeding practices.
Feed represents the largest expenditure item in semi-intensive and intensive culture systems and protein is the most expensive macro-nutrient in fish feeds. In semi-intensive tilapia farming where ponds are heavily fertilized, natural food organisms contribute significant amount of nutrient necessary for fish growth. Compounded feeds formulated for other species have been used as supplement to natural food to increase fish yield. However, due to the availability and high costs of compounded diets, a number of studies have been conducted to evaluate alternative cheap feed supplements for Nile tilapia farming. Such supplements that have been evaluated include rice bran, wheat bran, cassava meal and corn meal (Perschbacher and Lochmann, 1995; Cao et al., 1997; Veverica et al., 1999).
The problem with single ingredients like brans is that they are deficient in both macro and micro-nutrients while the high content of crude fiber in some brans may greatly reduce the digestibility thus, leading to low fish yields (Liti et al., 2001). However, preliminary studies conducted at Sagana fish farm have shown that the performance of different brans in promoting fish growth differed considerably. Maize bran, for example, gave the highest fish yield followed by wheat bran, while rice bran yielded the least. An alternative management practice to increase the fish yield is to use formulated diets.
In an attempt to seek ways of increasing fish yields, a recent study was conducted at Sagana fish farm to compare locally available rice bran with two compounded feeds, a domestic animal feed (pig finisher pellet) and a laboratory formulated diet (Liti et al., 2001). The results demonstrated that the two compounded diets had similar nutritional value and promoted better fish growth than rice bran.
Cao et al. (1997) compared the growth performance of O. niloticus fed 20% crude protein diets formulated from chicken feed and fish meal with single ingredients (corn meal and rice bran). The fish in this study performed better with formulated diets as compared to single ingredients. Also an economic comparison performed in this study favored the utilization of formulated diets.
Since the cost of feed represent the major expenses in semi-intensive tilapia production, reducing the cost of feed is necessary to increase profit. Compounded diets for pigs and starter/broiler diets, although locally available and have been shown to provided better growth of tilapia than brans, are very costly. Thus, lower-cost compounded diet formulated from locally available ingredients for semi-intensive production of O. niloticus in earthen ponds must be developed.
Quantified Anticipated Benefits
Twenty-five farmers will be provided with information on how to formulate economically effective practical diets at their farms. They will be reached through a worKShop to be conducted later after the experiment. The results of the study will help improve profitability in the production of O. niloticus, as determined by enterprise budgets, and will reduce reliance on feeds that are available only through special orders and at exaggerated prices. This knowledge will also empower farmers to become strong decision makers in the fish feed industry. Fish yield is expected to increase and the cost of feed is expected to be markedly reduced. For example, a 70-kg bag of commercial pig finisher pellet costs KSh 1,200 (US$15.60) while the costs of broiler starter and maize bran are KSh 1,400 (US$18.20) and 300 (US$3.90) respectively per 70 kg. A 70-kg bag of feed formulated from Nile perch filleting waste meal, cottonseed cake, sunflower oil meal residue, and maize bran to contain crude protein similar to that of starter/broiler feed would cost only KSh 850 (US$11.00) prior to pelleting. This is considerable cheaper than pig finisher pellets and starter/broiler feed.
The project will be conducted at Sagana Fish Farm, located at Sagana town which is 90 km north of Nairobi and located at an altitude of 1,230 m, latitude 0°39'S and longitude 37°12'E. Sixteen 800-m2 static water earthen ponds will be stocked with sex reversed male O. niloticus (10.0 g) at a rate of 2 fish/m2 (20,000 fish/ha). To control snails and to provide a second marketable species, 1,000/ha of fingerling Clarias catfish (5.0 g) will also be stocked. This stocking rate was previously shown to effectively control snail populations in station ponds. Prior to stocking and at every two weeks, ponds will be fertilized with inorganic fertilizers at rates previously determined at the site (20 kg and 5 kg of N and P/ha, respectively).
Two experimental diets will be formulated to contain approximately 20% crude protein and 6% fat. Diet 1 will consist of 8% Nile perch filleting waste, 20% cottonseed cake, 15% sunflower seed oil residue and 58% maize bran. Diet 2 will have the same composition as diet 1 except that 0.5% of fish vitamin premix will be added at the expense of maize bran. Available commercial starter/broiler diets will also be evaluated. Maize bran will be used as the control diet. All diets (except maize bran) will be processed into sinking pellets using belt driven mixer and extruder, broken down into suitable sizes and air dried to a moisture content of about 10%. Each diet will be fed to tilapia in four replicate ponds two times daily, once in the morning and once in the afternoon, at a daily rate of 2% of body weight. At least 10% of the total number of tilapia stocked in each pond will be sampled twice a month to determine the average weight and adjust the feeding rate. The ponds will be drained and harvested after 8 months of culture or until fish reach a marketable size of 300g , whichever comes first.
Fifty fish will be randomly selected at the beginning of the experiment and stored frozen at 8°C for determination of whole body proximate composition. At the conclusion of the feeding study, 10 fish from each pond will be randomly collected and stored frozen for subsequent measurement of body composition. Experimental diets will also be analyzed for chemical composition. Proximate analysis of fish and feeds swill be done following the standard method by AOAC (1990).
Weather data will be gathered from a meteorological station located at the farm. Morning and afternoon water temperature and dissolved oxygen at about 25 cm deep will be measured weekly at the start of the trial and more frequently as the experiment progressed. Total alkalinity, chlorophyll a, Secchi disk visibility, total ammonia-nitrogen, soluble reactive phosphorus, nitrate-nitrogen, nitrite-nitrogen, and total hardness will be measured once every two weeks. Total nitrogen and total phosphorus and will be analyzed monthly. All sampling and analyses of samples will be carried out according to the standard CRSP protocols.
The economic assessment of the diets will be determined by enterprise budget analysis, incorporating returns and variable costs (such as fingerlings, feedstuffs, transportation, labor).
Null hypothesis: There are no significant differences in the performance of all diets in terms of growth, total production, feed and protein efficiency, apparent protein utilization, whole body composition and production cost.
Statistical design and analysis: The experimental units (800-m2 ponds) will be assigned randomly using a completely randomized design with four replications/treatment. All data will be analyzed by a one-way analysis of variance (SAS Institute, 1993). Duncan's multiple range test will be used to determine differences between treatment means. Differences will be considered significant at the 0.05 probability level.
This proposed research form part of regional activities in Malawi, where the main research activity is pond management and nutrient inputs as means to increase fish production.
Preparation of ponds (draining and liming and fertilization), analysis of feed ingredients, and diet formulation and processing, July 2001. (Throughout the course of the study, due to the small capacity of the mixer and extruder, feed processing will be done as needed.)
Stocking of ponds with male sex-reversed O. niloticus and Clarias catfish, August 2001.
Harvesting of ponds, April 2002.
Chemical analysis of experimental feeds and fish, May to June 2002
Data analysis and final report submission, by 30 April 2003.
AOAC (Association of Official Analytical Chemists), 1990. Official Method of Analysis, 15th Edition. Association of Official Analytical Chemists, Arlington, Virginia.
Cao, T.B., C.K. Lin and H. Demaine, 1997. Evaluation of low cost supplemental diets for culture of Oreochromis niloticus (L.) in Northern Vietnam. In: D. Burke, J. Baker, B. Goetze, D. Clair and H. Egna (Editors), Fifteenth Annual Technical Report. Pond Dynamics/Aquaculture CRSP, Oregon State University, Corvallis, Oregon, pp. 167175.
Liti, D.M., E. Mac'Were, and K.L. Veverica, 2001. Growth performance and economic benefits of Oreochromis niloticus/Clarias gariepinus polyculture fed on three supplementary feeds in fertilized tropical ponds. World Aquaculture Society, 2001, Orlando, USA.
Perschbacher, P. W. and R. Lochmann, 1995. Effects of form of defatted rice bran offered on Nile Tilapia in production ponds. In: H. Egna, J. Bowman, B. Goetze and N. Weidner (Editors), Twelfth Annual Technical Report. Pond Dynamics/Aquaculture CRSP, Oregon State University, Corvallis, Oregon, pp. 7983.
SAS Institute. 1993. SAS User's Guide: Basics, 1993 Edition, Carey, North Carolina.
Veverica, K.L., W. Gichuri, and J. Bowman, 1999. Relative contribution of supplemental feed and inorganic fertilizers in semi-intensive tilapia production. In: K. McElwee, D. Burke, and H. Egna (Editors), Sixteenth Annual Technical Report. Pond Dynamics/Aquaculture CRSP, Oregon State University, Corvallis, Oregon, pp. 4345.
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