Proximate composition of selected potential feedstuffs for small-scale aquaculture in Ethiopia

A Kassahun, H Waidbacher and W Zollitsch*

BOKU-University of Natural Resources & Life Sciences Vienna, Department of Water, Atmosphere & Environment, Max- Emanuel-Straße 17, 1180 Vienna, Austria.
werner.zollitsch@boku.ac.at
* BOKU- University of Natural Resources & Life Sciences Vienna, Department of Sustainable Agricultural Systems

Abstract

In order to enhance aquaculture production, improve food security, and reduce the level of poverty in developing countries, a search for inexpensive and locally available feedstuffs is required. The present study surveyed selected potential feedstuffs with a specific focus on underutilized animal protein sources, agricultural and agro-industrial by-products. Selection of the feedstuffs was based on availability, cost and the avoidance of conflicts with human consumption. Proximate analysis was conducted of 40 selected feedstuffs from 6 underutilized animal protein sources and 34 plant feedstuffs from 7 categories to estimate their potential nutritive value for utilization as feedstuff for small-scale aquaculture.

Based on their proximate composition, 6 feedstuffs with highest CP and low NfE, from animal sources, were identified as potential dietary protein source, 16 feedstuffs with high CP and high NfE were identified as dietary protein and energy source and 11 feedstuffs with low CP and highest NfE were identified as dietary energy source.

Key words: by-product, energy, feed, fish, nutrients, protein, proximate analysis

Introduction

Fish feed play a major role in aquaculture viability and profitability, because it accounts for at least 40 - 60% of the total cost of fish production (Shang 1992; Craig and Helfrich 2002; Jamu and Ayinla 2003). Although there are rooms for enhancing aquaculture production in Africa through improvements in the overall production system, in genetics and general farm management principles, the desired growth of aquaculture which is necessary in order to meet the increasing demand for fish is only achievable through cost-effective and high quality fish feed (Gabriel et al 2007). Locally produced feed reduces the cost of production and hence, cheaper means of meeting the protein requirement improve food security and reduce the level of poverty in developing countries, thus inexpensive and locally available feedstuffs are to be identified. The search for alternative protein sources is to be focused on by-products and materials which are not suitable for direct human consumption (Hoffman et al 1997). However, in Ethiopia a number of by-products from agricultural processing is available, which are usually not utilized for human consumption, but may have a high potential for small-scale aquaculture. It is anticipated that the transformation of locally available by-products low in protein into high quality fish protein, can be a major contribution to improving the protein supply for the local human population.

Several agricultural and agro-industrial by-products available in Ethiopia have been evaluated for their production potential in poultry and livestock feed (Beker 1985; Lema 1992; Seyoum and Fekede 2006; Adugna 2007; Demeke 2007; Seyoum et al 2007; Negesse 2009; Tadessa et al 2009 a,b; Ajebu 2010). However, only few data are available which cover the suitability of this resource for fish feed (Adamneh et al 2007; Ashagrie et al 2008; Kassahun et al unpublished). Development of a feed for fish production involves evaluation of proximate composition of feed components, digestibility and performance efficiency as well as cost implications and conditions of application. Therefore, the current study was conducted to determine the proximate composition of selected locally available feed components for small-scale aquaculture feed development. A specific focus was put on currently underutilized animal protein sources, agricultural and agro-industrial by-products which are not consumed by the human population. Data from the current study are also expected to form the basis for further evaluation of the effects of selected feed components on digestibility and fish growth under different culture conditions.

Materials and Methods

The selection of feedstuffs to be covered within this study was based on availability, price and their non-use for human consumption. Samples were collected during a period of 18 months in typical regions of origin within Ethiopia (Table 1). Live Garra, Barbus and Aplocheilichthys species were collected from Lakes Koka, Ziway and Horra, respectively, using beach seain. The collection of adult sorghum chafer was done by simple traps which are baited with fruit peel (Ministry of Agriculture and Ethiopian Agricultural Research Organization 1999). The localities of samples analyzed in this study are presented in table 1.

Samples were sundried and ground into finer particles using an electric grinder and sieved through a 1 mm sieve. Analyses were conducted at the National Fisheries and Other Aquatic Life Research Center of the Ethiopian Institute of Agricultural Research in Sebeta, Ethiopia.

Dry matter (DM) was determined by drying 5 grams of sample according to AOAC (1995). Crude protein was quantified by the standard micro-Kjeldahl Nitrogen method as described in AOAC (2005), using a BehrosetInKje M digestion apparatus and a Behr S 1 steam distillation apparatus (Labor-Technik GmbH, Düsseldorf, Germany). The distilled ammonia was trapped in 2 % boric acid solution and titrated with 0.1N HCl. Crude protein was estimated by multiplying the nitrogen content with a factor of 6.25. Ether extracts were analyzed by extraction of samples of 2 g each in a Soxhlet extractor for 4 hours with diethyl ether (boiling point 40-60 °C). After extraction, the flask and extract was oven dried at 100°C for 1 hour, cooled in a desiccator for one hour and weighed. Ether extracts were quantified by expressing the difference in weight as a percentage of the original sample weight. Crude fiber (CF) was determined according to AOAC (2005). As CF is negligible in feedstuffs of animal origin, CF analysis was not conducted for feedstuffs of animal origin in the present study (CGIAR 2009). Ash was determined as the weight of the residue after 5 g of sample had been ashed at 550 °C in a muffle furnace overnight. Nitrogen Free Extracts were estimated by difference (DM-CP-EE-CF-Ash).

Results

Data on proximate composition of 40 selected feedstuffs from 7 categories are presented in tables 2-8. The proximate composition of feedstuffs of animal origin is presented in Table 2. Crude protein content ranges between 480 and 711g/kg DM. Within this group of feedstuffs, Sorghum chafer (Pachnoda interrupta) had the lowest CP content, while Garra sp had the highest. Ether extracts (EE) varied from 101 to 180 g/kg DM, which indicates a high energy content of these components. Among this group of feedstuffs, catfish carcass remains had the lowest EE level, while Sorghum chafer had the highest. The ash contents also varied between 34 (Sorghum chafer) and 282 g/kg DM (Catfish carcass remains). NfE contents were generally low.

The proximate composition of selected oilseed cakes is presented in Table 3. Crude protein contents range between 303 and 401g/kg DM. Among these feedstuffs, Nougseed cake had the lowest CP content, while soybean seed cake had the highest. Ether extracts were relatively low for soybean seed cake (81g/kg DM) and very high for sesame seed cake (187g/kg DM). Soybean seed cake contained relatively low quantities of CF and high levels of NfE, while the opposite was found for Nougseed cake.

The proximate composition of by-products from brewery and the production of wine and local beverage is presented in Table 4. The CP levels for this group of feedstuffs were highly variable (120 – 516g/kg DM): Grape pulp had the lowest, while dried brewery yeast from Harrar brewery had the highest. Overall, EE and ash values were moderate and ranged between 14 and 95g/kg DM and from 25 to 103g/kg DM, respectively. A relatively low CF level was found for areke-atela, while grape pulp contained extremely high amounts of CF and the other feedstuffs showed moderate to high CF contents. The highest NfE contents were found for Areke-atela.

The proximate composition of feedstuffs from different seed brans and hulls is presented in Table 5. The CP levels for this group range between 60 and 188 g/kg DM. Among this group of feedstuffs, chick pea hulls had the lowest CP, while lentil hulls had the highest. EE and ash levels in this group were found to be low. However, seed brans and hulls were generally rich in NfE. The CF levels varied from 41 to 426 g/kg DM for wheat bran and faba bean hull, respectively.

The proximate composition of feedstuffs from fruit peels and seeds is presented in Table 6. The CP levels for fruit peels and seeds range between 76 and 254 g/kg DM. Among these feedstuffs, mango peel had the lowest CP, while papaya seed had the highest. In this group, Avocado peels and Papaya seeds had the lowest and the highest EE level, respectively. The ash level of this group varied between 53 (Mango peel) and 188 g/kg DM (Papaya peel). The CF content of this group also varied between 113 (Banana) and 403 g/kg DM (Papaya peel). Papaya seed had the lowest level of NfE, while Mango peel had the highest.

The proximate composition of feedstuffs from boiled tea and coffee residue is presented in Table 7. The CP level of boiled tea residue was found to be higher than the CP in boiled coffee residues. The EE and ash level of both boiled coffee and tea residues were low. However, the CF level in boiled coffee residue was found be very high. Boiled tea residue was rich in NfE.

The proximate composition of feedstuffs from commercially formulated poultry feed and milling dust is presented in Table 8. The CP levels varied between 100 and 206 g/kg DM. Among these feedstuffs, milling dust from Deberezit had the lowest, while formulated poultry feed 2 had the highest CP content. EE, Ash and CF level in mill sweeping was lower than the EE, Ash and CF level in formulated poultry feeds. Generally mill sweepings and formulated poultry feeds were rich in NfE.

Discussion

Based on the data presented herein, 6 feedstuffs from animal origin with high CP and low NfE contents were identified as promising protein sources, 16 feedstuffs with high CP and high NfE were identified as sources for both protein and energy, and 11 feedstuffs with relatively low CP and high NfE were identified as promising energy sources (Fig 1, 2, 3). Dietary protein is used by fish for growth and body maintenance and eventually for energy supply. Thus a lack of high quality protein feed adversely affects growth rate, immune response to diseases and the total harvest of fish (Alatise et al 2006; Kaushik and Medale 1994). Since protein is a particularly expensive component in fish nutrition, any reduction in dietary protein level without affecting fish growth will substantially reduce the cost of fish feed (Jamabo and Alfred-Ockiya 2008). However, management, environmental factors and fish size can affect dietary nutrient level for optimum performance. Supplying energy from suitable sources in order to satisfy the energy requirements of fish will save dietary protein for growth (Jauncey 1998; Sang-Min and Tae-Jun 2005). High dietary fiber concentrations can lead to growth depression, due to various factors, such as faster gastric emptying, reduced feed intake, digestibility and nutrient utilization (NRC 1993). It is reported that at least 24% of CP was found to be essential for a satisfactory growth of O. niloticus under typical East African aquaculture conditions (Liti et al 2005). This minimum protein content for satisfactory growth of O. niloticus cannot be achieved with simplified diet formulations as they are commonly used by small scale producers in Ethiopia. However, fish perform well on feedstuffs containing even less than 200g/kg, such as wheat bran, maize bran, lathyrus pea bran and rice bran in fertilized ponds (Liti. et al 2006, Kassahun et al unpublished). Thus a CP content of 200g/kg is used herein as a limit for the selection of potential protein sources.

Tilapia and catfish carcass remains (i.e. post-filleting residues), small fish of various species of Aplocheilichthys, Garra, Barbus and insects were analysed as feedstuffs of animal origin with a generally very high CP content (Table 2 and 10). These feed materials are also expected to be highly digestible, to contain an excellent amino acid profile (i.e. especially high in lysine and methionine), a high percentage of poly-unsaturated and especially Omega -3 fatty acids. Due to this and the absence of ANFs, fishmeal is used as the main source of protein in fish feeds (Jauncey 1998; Hardy and Barrows 2002; El-Sayed 2004; Li et al 2006; Miles and Chapman 2006; Gatlin III et al 2007; Lin and Shiau 2007). Despite the lack of tradition of using fish meal as animal feed due to the poorly developed fishery and aquaculture sector in Ethiopia, small fish which form the by-catch from lake fisheries or carcass remains represent a currently underutilized, high quality nutrient pool for the nutrition of cultured fish. However, if relevant quantities of fishes are to be used for feed, special attention should be given to the ecological importance of these organisms in natural water bodies.

Insects may form another potential nutrient source for small scale aquaculture. The use of insects as fish feed supplement is not so common, but under natural condition fish feed on adult aquatic insects (Getachew 1987). The use of maggots has been reported to possess a great potential as fish feed by several authors (Adesulu and Mustapha 2000; Fasakin et al 2003; Ajani et al 2004; Ogunji et al 2008). These studies reported that the growth of fish has been promoted by feeding maggot meal. In the present study Sorghum chafer (Pachnoda interrupta) was analysed which temporarily occurs as an important pest in Ethiopia (Yitbarek and Hiwot 2000). The CP and EE contents of Sorghum chafer were found to be high (Table 2). Therefore, the utilization of Sorghum chafer as fish feed component would be advantageous from the perspective of eco-friendly crop protection, cost effectiveness and its nutritional value. The use of tilapia and catfish carcass remains, species of Aplocheilichthys, Garra, Barbus and Sorghum chafer as dietary protein sources in aquaculture feeds are also economically feasible, since the costs of supply mainly involved costs for collection, transportation and processing (Fig 1).

The data presented herein and information from the literature show that legume and oil seed cakes had high CP contents (Table 3; Table 10; Jackson et al 1982; El-Sayed 1990; Reddy 1999; Olvera et al 2002; Maina et al 2002; El-Saidy and Gaber 2004; Leming and Lember 2005; Munguti et al 2006; Guo et al 2011). The NfE values were moderate and the EE content of most of oil seed cakes was relatively high due to the incomplete oil extraction connected with the technologies practiced in Ethiopia (Table 3; Solomon 1992). This supports the use of these feedstuffs as energy supplements. Generally, oilseed cakes and legume seeds are considered suitable as alternative dietary protein and energy sources for fish feed and are available in Ethiopia and other regions of sub-Saharan Africa on large scale (Table 3; Fig 2; Fagbenro et al 2003). The level of inclusion in the feed depends on nutrients and toxic compounds in seed residues, which largely vary, depending on methods of processing and the strains used (Liener 1980). Oilseed cakes are commonly used for livestock feed in different parts of Ethiopia, also because of their moderate costs. In most developing countries leguminous seeds constitute an important part of the human diet and their use for aqua-feeds would compete with the ultimate goal of securing human nutrition. However, by-products from the processing of legume seeds and oilseeds are not directly used for human consumption in Ethiopia, therefore feed – food competition can be avoided.

Among the ingredients being investigated as alternatives to fish meal, soybean cake is the most promising (Table 3; Lim et al 1998; Hardy 1999; Storebakken et al 2000; Swick 2002) because of the security of supply, price as well as its protein and essential amino acid composition. Despite this favourable composition, the nutritional value of soybean cake may be lower than expected, mainly due to the presence of anti-nutritional factors, such as protease inhibitors, lectins, phytates and tannins (De la Pena et al 1987; Fagbenro 1998; Olli et al. 1994). The presence of these anti-nutritional factors reduces the growth rate of young mono-gastric animals (Van Damme et.al 1997), which requires removal or inactivation through processing prior to usage within aqua-feeds (Tacon 1995).

Several studies have been conducted to determine the amount of cotton seed cake, sesame seed cake and rapeseed cake that can be incorporated into fish diets without negative effects on growth (Yurkowski et al 1978; Jackson et al 1982; Viola and Zohar 1984; El-Sayed 1990; Gomes and Kaushik 1989; Hossain and Jauncey 1989a,b; Gomes et al 1993; Olukunle and Falaye 1998; Burel et al 2000; Mbahinzireki et al 2001; Rinchard et al 2002; El-Saidy and Gaber 2004; Yi-Rong and Qi-Cun 2008; Fagbenro 2010; Mazurkiewicz 2010; Nang et al 2011). Results have indicated that cottonseed cake contains gossypol which is toxic to fish. This has been reported to interfere with physiological processes of reproduction, including the inhibition of steroidogenesis in animals and a growth depression in fish (Table 9; Hadley et al 1981; Jauncey and Ross 1982; Lin et al 1988; Rinchard et al 2002; El- Saidy and Gaber 2004; Liti et al 2005). Rapeseeds contain high level of phytins, tannins and glucosinolates which limits its inclusion in fish feeds (Francis et al 2001). For successful utilization of these resources in aquafeed it requires removal or inactivation through processing prior to usage (Table 9; Jauncey and Ross 1982). While sesame seed is not known to contain any protease inhibitors, the high levels of oxalic and phytic acids may have adverse effects on palatability (Narasinga 1985; Johnson et al 1979) and on availability of minerals and protein (Aherne and Kennelly 1985). However, dehulling reduces the oxalic acid contact of the seed (Table 9; Salunkhe et al 1991). Linseed cake and noug seed cake (Guizotia abyssinica) are commonly used as livestock feed (Alemu and Guenther 1992; Tadesse and Zelalem 2004; Nudda 2006;Artur et al 2010). However, there are no data available for the effect of linseed cake and noug seed cake on the growth response of fish. The presence of hydrocyanic and phytic acid in linseed is likely to result in poor growth of monogastric animals but it can be extracted by water and heat (Table 9; Hossain and Jauncey 1990). There are also no reports on anti-nutritional factors in noug seed cake and as they were not analysed in the present study, a critical evaluation of anti-nutritional compounds is essential prior to widespread utilization.

The CP content of brewer´s grains was found to be higher than 200g/kg and it had high and moderate levels of NfE and CF, respectively (Table 3). The CP content of dried brewery yeast were very high and even comparable to that of feedstuffs from animal origin; it also contains high quantities of NfE (Table 3). Thus brewer´s grains and dried brewery yeast can serve as dietary sources for both protein and energy (fig 2). The CP levels of tela-atela, areke-atela and grape pulp were low, whereas they contained high amounts of NfE (Table 3). CF was low in tela-atela and areke-atela but high in grape pulp (Table 3). Thus tela-atela and areke-atela can be used as dietary energy source (Fig 3), but the high level of CF in grape pulp may limit its inclusion in the feed. Brewer´s grain has been fed to livestock since the advent of beer production (Wastendorf and Wohlt 2002). Brewer's grains, because of their high nutritive value, is widely available in many parts of the world. However, its utilization for animal diets, particularly for fish, is poorly understood in some regions (Desale et al 2008). Several studies indicated that the use of brewer´s by-products as fish meal substitute was successfully practiced in different fish species (Middendrop 1995; Hoffman et al 1997; Oliva-Teles and Goncalves 2001; Schneider et al 2004; Kaur and Saxena 2004; Desale et al 2008). Moreover, despite the inconsistency of the results from different studies it is reported that brewer´s yeast are capable of enhancing innate immunity and disease resistance of certain fish (Siwicki et al 1994; Li and Gatlin 2003; Li et al 2005). Tela-atela and areke-atela are produced in large amounts in almost every region of Ethiopia. Small proportions of this by-product are used as feed for dairy cattle and small ruminants. However, large quantities accumulate at production sites, causing disposal and public health problems (Demeke 2007). Several studies have been conducted on the nutritional effect of atella on dairy cows, small ruminants and poultry (Mekasha et al 2002; Mekasha et al 2003; Demeke 2007; Ajebu 2010), but here is no data available for the use of atella as fish feed. Brewery by products are usually very cheap and readily available at production sites throughout the country, and areke-atela, tela-atela and grape pulp are usually available for free. Therefore, the use of these by-products as aquaculture feeds will also be economically feasible.

Figure 3. Selected potential energy sources for small-scale aquaculture in Ethiopia BD= Baher Dar, DZ = Debere Zit, Se = Sebeta

Except for wheat bran, seed brans and hulls analysed in this study contained high levels of CF (Table 4). Although seed brans and hulls can be considered as dietary energy sources, their mostly high CF content will limit their inclusion level in the feed. The use of cereal brans and hulls is very common as livestock feed in Ethiopia, but its use as fish feed has only recently been evaluated: wheat bran and Lathyrus pea hull were fed to O. niloticus and the growth performance in fertilized and unfertilized ponds was evaluated (Kassahun et al unpublished data; Adamneh et al 2007). Both wheat bran and Lathyrus pea hull promoted good growth of Nile tilapia and can substitute each other, depending on whichever of the two is locally available (Kassahun et al unpublished). In a similar study in Kenya it is reported that wheat bran and maize bran promoted growth of O. niloticus in fertilized ponds (Liti et al 2006). Gohl (1975) found a general deficiency of lysine in cereal by-products, but deficient nutrients might be supplemented by natural pond food in semi-intensive culture systems. Thus, based on their proximate composition and results from growth experiments, wheat bran, barley bran and Lathyrus pea hull can be used as potential energy sources in aquaculture feed development (fig 3). The presence of protease inhibitors, phytohaemagglutinin and saponin in lentil hulls, which could reduce apparent digestibility of protein and lipid, and inhibit absorption of vitamin and cholesterol metabolism may limit the use of lentil hulls in aquafeed (Table 8; Berg-Lea et al 1989; Ashild et al 2010). Thus, due to the presence of antinutritional factors and the high CF content of chick pea hulls, lentil hulls and faba bean hulls are not recommended to be used as aquafeeds. The use of cereal brans and hulls is economically promising as they are cheap and readily available in most Ethiopian regions.

In some Ethiopian regions, large quantities of fruit by-products accumulate at production and market sites without being utilized and therefore causing disposal and public health problems. The CP levels in most fruit by-products analysed were very low except for papaya peel and seeds (Table 5). While papaya peel and seeds were high in CF and low in NfE, the other fruit by-products analysed had low CF and high NfE (Table 5). Although there is hardly any data available about the use of fruit by-products as livestock or fish feed, papaya peel and papaya seeds might have a value as dietary protein sources. However, their high CF content and their content of lectins which are potentially toxic for fish (Table 8; Makkar and Becker 1999; Asseliech et al 1989), and would have to be destroyed by heat treatment followed by aqueous methanol extraction or soaking in water for 24 hours under refrigerated conditions (Makkar and Becker 1999) will probably prevent their practical utilization. Banana peels, mango peel and avocado peel could be used as dietary energy sources. From an economical point of view, the use of any fruit by-product seems to be promising, as the only costs to be considered are for collection, transportation and eventually some kind of moderate processing.

Boiled coffee residue is a by-product of a very popular beverage used in all parts of the country. The nutritional level of boiled coffee residue, however, was found to be poor, due to low CP, EE, NfE and high CF (Table 6). No data and information is available on proximate composition and the use of this by-product as animal or fish feed. Due to its low nutrient content, boiled coffee residues will not be recommended as potential feed component for small-scale aquaculture. However, it is readily available and accessible in all part of the country and there is no conflict of interest with livestock feeding. Therefore it might offer a cheap source for fertilizing ponds, provided that the secondary constituents like caffeine are not harmful to fish. While there is no data available for the effect of caffeine on fish, it is reported that caffeine has health hazards on humans if it exceeds a certain level (Nawrot et al 2003). Other than coffee residues, boiled tea leaf residues, which are widely available in cities and towns, contains high levels of CP and NfE, only moderate level of CF and very low EE (Table 6, 10; Munguti et al 2006). Therefore they may be considered as potential source for protein and energy for small-scale aquaculture, but no data is available for their use as livestock or fish feed. However, a critical evaluation of anti-nutritional compounds is essential prior to their utilization.

Due to the lack of commercially prepared aquafeed, poultry feeds are frequently used as fish feed for projects and experiments in Ethiopia. The nutritional value of the formulated poultry feeds from three different sources which were analysed in this study, was found to be similar, with CP being around 200g/kg, low CF and high NfE (Table 7). From the nutrition point of view, these feedstuffs may be used for small-scale aquaculture as protein and energy sources, but their high price may prevent them from being utilized on a larger scale. Although there was some variation in the CP contents of milling dusts, their CP level was generally low. However, all milling dusts were rich in NfE and low in CF (Table 7). Milling dusts are commonly used as livestock feed in Ethiopia, but very few data are available for the use of this by-product as fish feed ingredient (Ashagrie et al 2008). From a nutrition point of view, milling dusts may be a good alternative energy source for small-scale aquaculture. Milling dusts are generally cheap and readily available in most Ethiopian regions, thus the use of milling dusts is likely to be economically feasible.

Conclusions

• From the present study and from the information provided in the literature it can be concluded that Tilapia and Catfish carcass remains, Aplocheilichthus sp, Barbus sp, Garra sp and Sorghum chafer can be used as dietary protein sources. Brewer´s grain, dried brewery yeast, oil seed cakes, formulated poultry feeds can be used as both dietary protein and energy sources. Areke-atela, tela-atela, brans and hulls from different seeds, banana, mango and avocado peels, and milling dust can be used as dietary energy sources in aquaculture systems which rely greatly on local resources. This estimation is mainly based on the actual contents of CP, NfE and CF, but the possibility and practicability of removing anti-nutritional constituents, the evaluation of amino acid contents and digestibility needs to be addressed by further research. If relevant quantities of fishes are to be used for feed, special attention should be given to the ecological importance of these organisms in natural water bodies. Furthermore, the use of fish protein should not be targeted as a common option for the production of fish feed for small-scale, sustainable aquaculture, but should be mainly utilized for feeding fry which particularly requires high quality protein sources.

Acknowledgements

The authors are grateful to the Austrian Development Cooperation through ÖAD North-South Dialogue Programme and BOKU-University of Natural Resources and Life Sciences Vienna for financial support. We appreciate the support from the Ethiopian Institute of Agricultural Research (EIAR) and the cooperation of staff from National Fishery and other Aquatic Life Research Centre (NFLARC). Support received from Holetta Agricultural Research Centre, Animal Nutrition Department staff and National Animal health research is also are greatly acknowledged.

References

Adamneh D, Aschale H, Fassil D and Abeba W 2007 Growth performance and economic returns of male monosex and unsexed tilapia (Oreochromis niloticus L.) culture in ponds fed on wheat bran. In: Live stock systems: Opportunities and challenges as a livelihood strategy, D. Tamerat and F. Fekede (eds), pp 172-179. Proceedings of the 15^th annual conference of the Ethiopian Society of Animal Production (ESAP), Addis Ababa-Ethiopia.

ADCP 1983 Fish feeds and feeding in developing countries. Rome, FAO, ADCP/REP/83/18, 97 p.

ADCP 1987 Feed and feeding of fish and shrimp-a manual on the preparation and presentation of compound feeds for shrimp and fish culture. Rome, FAO, ADCP/REP/87/26,184-193 pp.

Adesulu E A and Mustapha A K 2000 Use of housefly maggots as a fishmeal replacer in tilapia culture: a recent vogue in Nigeria. In: 5th Inter. Symp. On tilapia Aquaculture (Fitzsimmons, K. & Filho, J.C. eds.) Vol. 1, pp. 138. Rio De Janeiro, Brasil.

Adugna T 2007 Feed resource for producing export quality meat and livestock in Ethiopia. Examples from selected woredas in Oromia and SNNP regional states

Aherne F X and Kennelly J J 1985 Oilseed meals for livestock feeding. In: Recent developments in pig nutrition. Eds. Cole, D.J.A. & Haresign, W., Butterworths, London. pp. 278-315.

Ajani E K, Nwanna L C and Musa B O 2004 Replacement of fishmeal with maggot meal in the diets of Nile tilapia, Oreochromis niloticus. World Aquaculture, 35/1: 52-54.

Ajebu N 2010 Feed intake, digestibility, nitrogen utilization and body weight change of sheep consuming wheat straw supplemented with local agricultural and agro-industrial by-products. Tropical Animal Health and Production (2010) 42: 815 – 824

Alatise P S, Ogundele O, Eyo A A and Oludunjoye F 2006 Evaluation of different soybean- based diets on growth and nutrient utilization of Heterobranchus longifilis in aquaria tanks. FISON conference Proceeding. Calabar 13th-17th Nov. 2006. pp. 255-262.

Alemu Y and Guenther K D 1992 Studies on the chemical composition of some poultry feeds of Ethiopian origin. Beitrage zur Tropischen Landwirtschaft und Veterinarmedizin, 30, 427 – 450.

AOAC (Association of Official Analytical Chemists) 1995 Official Methods of Analysis. 16th Edition.AOAC, Arlington, VA. USA.

AOAC (Association of Official Analytical Chemists) International 2005 Official Methods of Analysis of AOAC International, 18^th Edition. Gaithersburg, Maryland, USA, AOAC International.

Artur J, Nina S, Emilia B, Zbigniew Ł, Bożena P, Wojciech C, Agnieszka C, Weronika G, Danuta S, Józef K and Jarosław O H 2008 The effect of feeding linseed cake on milk yield and milk fatty acid profile in goats. Animal Science Papers and Reports vol. 28 (2010) no. 3, 245-251 Institute of Genetics and Animal Breeding, Jastrzębiec, Poland

Ashagrie G, Abebe G and Seyoum M 2008 Effect of stocking density on the growth performance and yield of Nile tilapia [Oreochromis niloticus (L., 1758)] in a cage culture system in Lake Kuriftu, Ethiopia, Aquaculture Research, 2008, 39, 1450 – 1460

Ashild K, Michale P, Jim T, Stale R and Anne M B 2010 Important antinutrients in plant feedstuffs for aquaculture: an update on recent findings regarding responses in salmonids, Aquaculture Research, 2010, 41, 333-344

Asseliech C L M, Plumbly R A and Hyslands P J 1989 Purification and partial characterization of the hemagglutination from seeds of Jatropha curcas. Journal of Food Biochemistry, 13, 1-20.

Assmann S 2009 Feeding behavior of Nile tilapia (Oreochromis niloticus) according to feeds made of locally available agriculture by-products in Kenya, East Africa Master thesis, BOKU University of Natural Resource and applied life science, Vienna, Austria

Beker A 1985 Evaluation of the nutritive value of brewers’ grain to chicks. M.Sc. Thesis. Addis Ababa University, 1 pp.

Berg L T, Bratts L E and Krogdahl A 1989 Soybean proteinase inhibitors affect nutrient digestion in rainbow trout. In: Recent Advances of Research in Antinutritional Factors in Legume Seeds (ed. by J. Huisman,T.F.B. van der Pool & I. Liener), pp.99 - 102. Pudoc,Wageningen.

Burel C, Boujard T, Escaffre A M, Kaushik S J, Boeuf G, Mol K A, van der Geyten S and Kühn E R 2000 Dietary lowglucosinolate rapeseed meal affects thyroid status and nutrient utilization in rainbow trout (Oncorhynchus mykiss). British Journal of Nutrition, 83, 653–664.

CGIAR 2009 Sub-saharan Africa feed composition database - ILRI Lab data. CGIAR Systemwide Livestock Programme

Craig S and Helfrich L A 2002 Understanding Fish Nutrition, Feeds and Feeding, Cooperative Extension Service, publication 420-256. Virginia State University, USA.

De la Pena, L D, Chiu Y N and Ganchero F 1987 “Evaluation of various leguminous seeds as protein sources for milkfish, Chanos chanos Forrskal, juveniles”. Asian Fisheries Science 1:19-25.

Demeke S 2007 Comparative nutritive value of Atella and industrial brewers grains in chicken starter ration in Ethiopia. Livestock Research for Rural Development. Volume 19, Article #8.Retrieved May 26, 2011, from http://www.lrrd.org/lrrd19/1/deme19008.htm

Desale B Z, Kevin M F, Robert J C and Glenn C D 2008 Evaluation of Brewer´s waste as partial replacement of fish meal protein in Nile Tilapia, Oreochromis niloticus, Diets. Journal of the world Aquaculture Socity.Vol. 39 N0. 4

Dong N T K and Ogle R B 2004 An evaluation of Brewery Waste as a Replacement for Concentrates in Diets for Growth Crossbred Common Ducks. Tropical Animal Health and Production, 36 715 – 729.

El-Saidy D M S D and Gaber M M A 2004 Use of cottonseed meal supplemented with iron for detoxification of gossypol as a replacement of fish meal in Nile tilapia, Oreochromis niloticus (L.) diets. Aquaculture Research 35,859 - 869.

El-Sayed A-F M 1990 Long-term evaluation of cottonseed meal as a protein source for Nile tilapia, (Oreochromis niloticus L.) Aquaculture, 84, 315-320.

El-Sayed A-F M 2004 Protein nutrition of farmed tilapia: searching for unconventional sources. In: Bolivar R B, Mair G C and Fitzsimmons K (editors), Proceedings of the 6th International symposium on Tilapia in Aquaculture, Manila, Philippines Volume 1 pp 364-378

Fagbenro OA 1998 “Apparent digestibility of legume seeds by Nile tilapia”. Aquaculture International 6: 83-87.

Fagbenro O A, Akande T T and Fapounda O O 2003 Use of Roselle (Hibiscus Sabdariffa) seed meal as a soybean meal replacer in practical diets for fingerlings of African Catfish (Clarias gariepinus). Proceeding of the third international conference on African fish and Fisheries, Cotonou, Benin, 10-14 November, Ed SnoeksJ, Laleye P, Vandewalle P. p. 73-79.

Fagbenro O A, Adeparusi E O and Jimoh W A 2010 Nutritional evaluation of sunflower and sesame seed meal in Clarias gariepinus: An assessment by growth performance and nutrient utilization African Journal of Agricultural Research Vol. 5(22), pp. 3096-3101.

Fasakin E A, Balogun A M and Ajayi O O 2003 Evaluation of full fat and defatted maggot meals in the feeding of calariid catfish calarias gariepinus fingerlings. Aquaculture research 34, 733-738.

Francis G, Makkar H P S and Becker K 2001 Antinutritional factors present in plant-derived alternate fish feed ingredients and their effects in fish. Aquaculture 199, 197–227.

Gabriel U U, Akinrotimi O A, Bekibele D O, Onunkwo D N and Anyanwu P E 2007 Locally produced fish feed: potentials for aquaculture development in sub-Saharan Africa African Journal of Agricultural Research Vol. 2(7), pp. 287-295.

Gatlin III D M, Barrows F T, Brown P, Dabrowski K, Gaylord T G, Hardy R W, Herman E, Hu G, Krogdahl A, Nelson R, Overturf K, Rust M, Sealey W, Skonberg D, Souza E J, Stone D, Wilson R and Wurtele E 2007 Expanding the utilisation of sustainable plant products in aquafeeds: a review. Aquaculture Research 38: 551-579

Getachew T 1987 A study of an herbivorous fish, Oreochromis niloticus L., diet and its quality in two Ethiopian Rift valley Lakes, Awasa and Zwai. Journal of Fish Biology 30, 439-449.

Gohl B 1975 Tropical feeds. Food and Agricultural Organisation of the United Nations, Rome, Italy. p 525.

Gomes E F and Kaushik S J 1989 Incorporation of lupin seed meal, colzapro or triticale as proteinrenergy substitutes in rainbow trout diets. In: Proc. Third Int. Symp. on Feeding and Nutr. in Fish, Toba, Tokyo University, Japan, 1989, 28 aout–1er septembre. pp. 315–324.

Gomes E F, Corraze G and Kaushik S 1993 Effects of dietary incorporation of a co-extruded plant protein (rapeseed and peas) on growth, nutrient utilization and muscle fatty acid composition of rainbow trout (Oncorhynchus mykiss). Aquaculture, 113, 339–353.

Guo Y X, Xiao-Hui D, Bei-Ping T, Shu-Yan C, Qi-Hui Y, Gang C and Lu Z 2011 Partial replacement of soybean meal by sesame meal in diets of juvenile Nile tilapia, Oreochromis niloticus L. Aquaculture Research, 42, 1298 – 1307.

Hadley M A, Lin Y C and Dym M 1981 Effects of gossypol on the reproductive system of male rats. Journal of Andrology 1981, 2190–2199.

Hardy R W 1999 Collaborative opportunities between fish nutrition and other disciplines in aquaculture: an overview. Aquaculture Vol 177 No.1-4 pp 217-230.

Hardy R W and Barrows F T 2002 Diet formulation and manufacture. In: Halver J and Hardy R (editors), Fish Nutrition 3^rd Edition Academic Press, New York, NW, USA, pp. 505-600.

Hoffman L C Prinson J F and Rukan G 1997 Partial replacement of fish meal with either soybean meal or brewery yeast or tomato meal in the diet of African sharp tooth Catfish Clarias gariepinus. Water SA 23(2), 181 – 186.

Hossain M A and Jauncey K 1989a Study on protein, energy and amino acid digestability of fish meal, mustard oil cake, linseed and sesame meal for Common carp (Cyprinus carpio). Aquaculture, 83, 59 – 72.

Hossain M A and Jauncey K 1989b Nutritional evaluation of some Bangladeshi oil seed meal as partial substitutes for fish meal in the diet of Common carp (Cyprinus carpio). Aquaculture and Fisheries Management, 20, 255 – 268.

Hossain M A and Jauncey K 1990 Detoxification of linseed and sesame meal and evaluation of their nutritive in the diet of Common carp (Caprius carpio L). Asian Fisheries Science, 3, 169 – 183.

Jackson A K, Capper B S and Matty A J 1982 Evaluation of some plant proteins in complete diets for the tilapia (Sarotheron mossambicus). Aquaculture 27, 97-109.

Jamabo N A and Alfred-Ockiya J F 2008 Effects of dietary protein levels on the growth performance of Heterobranchus bidorsalis (Geoffroy-Saint-Hilaire, 1809) fingerlings from the Niger Delta. African Journal of Biotechnology Vol. 7 (14), pp. 2483-2485.

Jamu D M and Ayinla O A 2003 Potential for the development of aquaculture in Africa. NAGA 26(3), 9-13, http://worldfishcenter.org/Naga/naga26_3.htm

Jauncey K 1998 Tilapia feeds and feeding. Pisces Press Ltd, Stirling-Scotland.

Jauncey K and Ross B 1982 A guide to tilapia feeds and feeding. Institute of Aquaculture. University of Stirling, Scotland. U.K

Jonson L A, Suleima T M and Lusas E W 1979 Sesame protein: a review and prospect. Journal of the American Oil Chemists' Society, 56, 463 – 468.

Kaur V I and Sexena PK 2004 Incorporation of brewery waste in supplementary feed and its impact on growth in some carps. Bioresource Technology 91: 101 – 104.

Kaushik S J and Medale F 1994 Energy requirement utilization and dietary supply of salmonids. Aquaculture 124: 81 – 97.

Leming R and Lember A 2005 Chemical composition of expeller-extracted and cold-pressed canola meal. Agraarteadus 16:103–109.

Lemma G 1992 Comparison of different legumes hay, urea, and noug seed cake as a protein supplement for growing Horro sheep fed teff straw. In: Proceedings of the 4th National Livestock Improvement Conference, 13–15 November 1991, Addis Ababa, Ethiopia, pp. 211–215.

Liener I E 1980 Introduction. In: Toxic constituents of plant foodstuffs (ed. I.E. Liener), pp 1-6. Academic Press, New York, USA.

Liener I E 1994 Implications of antinutritional components in soybean foods. Critical reviews in food science and nutrition, 34(1), 31-67.

Li M H, Lim C E and Webster C D 2006 Feed formulation and manufacture. In: Lim C E and Webster C D (editors), Tilapia Biology, Culture, and Nutrition, Haworth Press Inc, New York, London, pp. 517-545.

Lin Y C, Dietrick T and Rukihisa Y 1988 Antifertility effect of gossypol in male Japanese quail. Life Sciences, 42, 2283-2292.

Lin Y H and Shiau S Y 2007 Effect of dietary blend of fish oil with corn oil on growth and non-specific immune responses of grouper, Epinephelus malabaricus. Aquaculture Nutrition 13, 137-144.

Li P and Gatlin III D M 2003 Evaluation of brewer`s yeast, (Saccharomyces cerevisiae) as a feed supplement for hybrid striped bass, (Morone chrysops X M. saxatilis). Aquaculture 219, 681–692.

Li P, Burr G S, Goff J, Whitemen K W, Davis K B, Vega R R, Neill W H and Gatlin III D M 2005 A preliminary study on the effect of dietary supplementation of Brewers yeast and nucleotides, singularly or in combination, on juvenile red drum, Sciaenops ocellatus. Aquaculture Research 36, 1120– 1127.

Liti D, Cherop L, Munguti J and Chhorn L 2005 Growth and economic performance of Nile tilapia (Oreochromis niloticus L.) fed on two formulated diet and two locally available feeds in fertilized ponds. Aquaculture Research, 2005, 36, 746- 752.

Liti D M, Mugo R M, Munguti J M and Waidbacher H 2006 Growth and economic performance of Nile tilapia (Oreochromis niloticus L.) fed on three brans (maize, wheat and rice) in fertilized ponds. Aquaculture Nutrition12, 239–245.

Maina J G, Beames R M, Higgs D, Mbugua P N, Iwama G and Kisia S M 2002 Digestibility and value of same feed ingredients fed to tilapia Oreochromis niloticus (L). Aquaculture Research 33, 853-862.

Makkar H P S and Becker K 1999 Plant toxins and detoxification methods to improve feed quality of tropical seeds-Review. Asian-Australian Journal of Animal Science 12 (3), 467-480.

Mazurkiewicz J, Przybyl A, Czyzak-runowska G and Lyczynski A 2010 Cold-pressed rapeseed cake as a component of the diet of common carp (Cyprinus carpio L.): effects on growth, nutrient utilization, body composition and meat quality. Aquaculture Nutrition 2010.1111/j.1365-2095.2010.00811.x

Mbahinzireki G B, Dabrowski K, Lee K J, El-Saidy D and Wisner E R 2001 Growth, feed utilization and body composition of tilapia (Oreochromis sp.) fed with cottonseed meal-based diets in a recirculating system. Aquaculture Nutrition 7, 189–200.

Mekasha Y, Tegegne A, Yami A and Umunna NN 2002 Evaluation of non-conventional agro-industrial by-productsas supplementary feeds for ruminants: in vitro and metabo-lism study. Small Ruminant Research 44, 25-35.

Mekasha Y, Tegegne A, Yami A, Umunna N N and Nsahlai I V 2003 Effects of supplementation of grass hay with non-conventional agro-industrial by-products on rumen fermen-tation characteristics and microbial nitrogen supply in rams. Small Ruminant Research 50, 141-151.

Middendorp A J 1995 Pond farming of Nile tilapia, Oreochromis niloticus (L.), in northern Cameroon. Feeding combinations of cottonseed cake and brewery waste in fingerling culture, hand-sexed male monosex culture, and mixed culture with police-fish, Clarias gariepinus (Burchell). Aquaculture Research, 26,715–722. doi:10.1111/j.1365-2109.1995.tb00863.x

Miles R D and Chapman F A 2006 The benefits of fish meal in aquaculture diets. Series of the Department of Fisheries and Aquatic Sciences University of Florida. FA 122, pp 7 http://edis.ifas.ufl.edu/FA122

Ministry of Agriculture, and Ethiopian Agricultural Research Organization (EARO) 1999 Control measures used by farmers and associated problems Workshop on the Significance, Distribution, and Control of Sorghum Chafer, Pachnodainterrupta (Olivier) (Coleoptera: Scarabaeidae) in Amhara and Afar regions, Ministry of Agriculture and Ethiopian Agricultural Research Organization, Addis Ababa, Ethiopia, pp. 19–23.

Munguti J M, Liti D M, Waidbacher H, Straif M and Zollitsch W 2006 Proximate composition of selected potential feedstuffs for Nile tilapia (Oreochromis niloticus Linnaeus) production in Kenya, Austrian journal of Agricultural research 57 (3), 131 – 141.

Narasinga R M S 1985 Nutritional aspect of oil seeds. In oil seed productions – contraints and opportunities ed. Strvastava HC, Bhaskaran S, Vatsya B, Menon KKG. P. 625 – 34, New Delhi, Oxford and IBH.

National Research Council (NRC) 1993 Committee on Animal Nutrition (Board on Agriculture) Nutrient requirement for fish. National Research council, National Academy Press, Washington, DC.

Nang T T T, Bodin N, Saeger D E, Larondelle Y and Rollin 2011 Substitution of fish meal by sesame oil cake (Sesamum indicum L.) in the diet of rinbow trout (Oncorhychus mykiss W.) Aquaculture Nutrition 17, 80-89.

Nalwanga R, Liti D M, Waidbacher H, Munguti J and Zollitsch W J 2009 Monitoring the nutritional value of feed components for aquaculture along the supply chain – an East African case study. Livestock Research for Rural Development. Volume 21, Article #148. Retrieved April 8, 2011, from http://www.lrrd.org/lrrd21/9/nalw21148.htm

Nawrot P, Jordan S, Eastwood J, Rotstein J, Hugenholtz A and Feeley M 2003 Effects of caffeine on human health Food Additives and Contaminants, Vol. 20, No. 1, 1–30.

Negesse T, Makkar H P S and Becker K 2009 Nutritive value of some non-convectional feed resources of Ethiopia determined by chemical composition analysis and an in vitro gas method. Animal feed Science and Technology 154: 204 – 217.

Nudda A, Battacone G, Usai M G, Fancellu S and Pulina G 2006 Supplementation with Extruded Linseed Cake Affects Concentrations of Conjugated Linoleic Acid and Vaccenic Acid in Goat Milk. Journal of Dairy Science 89, 277–282.

Ogunji J O, Rahat-Ul-Ain S T, Carsten S and Werner K 2008 Growth Performance, Nutrient Utilization of Nile Tilapia Oreochromis niloticus Fed Housefly Maggot Meal (Magmeal) Diets. Turkish Journal of Fisheries and Aquatic Sciences 8. 141-147.

Oliva-Teles A and Goncalves P 2001 Partial replacement of fish meal by brewer´s yeast, Saccaromyces cerevisae, in diets for sea bass, Dicentrarchus labrax, juveniles. Aquaculture 202, 269–278.

Olli J, Hjelmeland K and Krogdahl A 1994 Soybean trypsin inhibitors in diets for Atlantic salmon (Salmo salar, L.): effects on nutrient digestibilities and trypsin in pyloric caeca homogenate and intestinal content. Comparative Biochemistry and Physiology 109A, 923–928.

Olvera-Novoa M A, Olivera-Castillo L  and Martinezpalcios C A 2002 Sunflower seed meal as a protein source in diets for Tilapia rendalli (Boulanger, 1896) fingerlings. Aquaculture Research 33, 223-229.

Osman M A, Reid P M and Weber C W 2002 Thermal inactivation of tepary bean (Phaseolus acutifolius), soybean and lima bean protease inhibitors: effect of acidic and basic pH. Food Chemistry 78, 419-423.

Phatcharaporn W, Siripan J and Sorada W 2009 The effects of banana peel preparations on the properties of banana peel dietary fibre concentrate Songklanakarin Journal of Science and Technology 31 (6), 605-611.

Reddy C A 1999 Feeding sesame seed meal. Poultry International 38, 90-94.

Rinchard J, Mbainzireki G, Dabrowski K, Lee K J, Garcia-Abiabo M A and Ottobre J 2002 The effects of cottonseed meal protein level on growth, gonad development and plasma sex steroid hormones of Tropical fish Tilapia, Oreochromis sp. Aquaculture International 10, 11-28.

Salunkhe D K, Chavan J K, Adsule R N and Kadam S S 1991 World oilseeds: Chemistry, Technology and Utilization. P. 554. New York. Van Nostrand Reinhold.

San-Min T and Tae-Jun L 2005 Effects of dietary protein and energy levels on growth and lipid composition of juvenile snail. Journal of Shellfisheries Research, Jan 2005, pp. 50-65.

Schneider O, Amirkolaie A K, Vera-Cartas J, Eding E H, Schrama J W and Verreth J A J 2004 Digestibility, feces recovery, and related carbon, nitrogen and phosphorus balances of five feed ingredients evaluated as fish meal alternatives in Nile tilapia, Oreochromis niloticus L. Aquaculture Research 35, 1370–1379.

Seyoum B and Fekede F 2006 The status of animal feeds and nutrition in the West Shewa zone of Oromia, Ethiopia. In: (Kindu, M., Glatzel, G. and Habermann, B. eds) Proceedings of indigenous trees and shrub species for environmental protection and agricultural productivity. Workshop at Holetta Agricultural Research Center; November 7-9, 2006, Ethiopia. Pp 27-49.

Seyoum B, Zinash S and Dereje F 2007 Chemical composition and nutritive values of Ethiopian feeds. Ethiopian institute of agricultural research. Research report 73.

Shang Y C 1992 “The Role of Aquaculture in the World Fisheries”, Presented at the World Fisheries Congress, Athens, Greece, May 3-8, 30pp.

Siwicki A K, Anderson D P and Rumsey G L 1994 Dietary intake of immunostimulants by rainbow trout affects non-specific immunity and protection against furunculosis. Veterinary Immunology and Immunopathology 41, 125–139.

Solomon M 1992 The effects of method of processing of oil seed cakes in Ethiopia on nutritive value. PhD Thesis, University of Bonn, Germany.

Storebakken T, Refstie S and Ruyter B 2000 Soy products as fat and protein sources in fish feeds for intensive aquaculture. Soy in Animal Nutrition (ed. by Drackley, J.K), Federation of Animal Science Societies, Savoy, IL, USA, 127-170.

Swick R A 2002 Soybean meal quality: assessing the characteristics of a major aquatic feed ingredient. Global Aquaculture Advocate 5, 46-49.

Tacon A G J 1995 Fishmeal replacers: review of antinutrients within oilseeds and pulses - a limiting factor for the aquafeed green revolution. Paper presented at the Feed Ingredients Asia’95 Conference, 19-21 September 1995, Singapore International Convention & Exhibition Centre, Singapore. Turret Group PLC (UK), Conference Proceedings, pp.23-48.

Tadessa D, Getu K, Aemiro K, Seyoum B, Dereje F, Bayissa H and Liyusew A 2009a Feed Resource Status, LivestockFeeding and Management in the Central Highlands of Ethiopia. Proceedings of Ethiopian society of animal production 17th-ESAP-TP-005.

Tadessa D, Fassil A and Seyoum B 2009b Reaction of Some Rumen Micro flora to Different Supplementary Feeds in Rumen Fistulated Animals. Ethiopian Journal of Science (SINET) 32(1), 65-74

Tadesse B and Zelalem Y 2004 Feeding noug 'Guizotia abyssinica' cake as protein source to lactating Borana X Jersey crossbred cows: performances in milk yield, reproduction and feed efficiency. PP. 375-385. In: Farm animal biodiversity: status and prospects. Proceedings of the 11^th Annual Conference of the Ethiopian Society of Animal Production (ESAP). 28-30 August 2003, Addis Ababa, Ethiopia.

Van Damme E J M, Peumans W J, Pusztai A and Bardocz S 1997 Handbook of plant lectins: Properties and biomedical applications, p. 224. Chichester: Wiley.

Viola S and Zohar G 1984 Nutrition studies with market size hybrids of tilapia Oreochromis in intensive culture. The Israeli Journal of Aquaculture-Bamidgeh 36, 3-15.

Westendorf M L and Wohlt J E 2002 Brewing byproducts: their use as animal feeds. The Veterinary Clinics of North America Food Animal Practice 18(2), 233–252.

Yi-Rong Y and Qc-Cun Z 2008 Effect of replacing soyabean meal with cottonseed meal on growth, feed utilization, and hematological indexes for juvenile hybrid tilapia, Oreochromis niloticus X O. aureus. Aquaculture 284, 185 – 189.

Yitbarek W H and Hiwot L 2000 Yield loss assessment of sorghum chafer, Pachnoda interrupta (Coleoptera: Scarabaeidae), in Ethiopia. Workshop on the Development of Monitoring and Control Strategy Against Sorghum Chafer, Pachnoda interrupta (Coleoptera: Scarabaeidae) in Ethiopia, Ministry of Agriculture, Addis Ababa, Ethiopia, pp. 40–43.

Yurkowski M, Bailey J K, Evans R E, Tabaczek G B, Ayles G B and Eales J G 1978 Acceptability of rapeseed proteins in diets of rainbow trout (Salmo gairdneri). Journal of the Fisheries Research Board of Canada 35, 951–962.

Received 1 January 2012; Accepted 26 May 2012; Published 1 June 2012

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