TILAPIA FEED AND FEEDING IN SEMI-INTENSIVE CULTURE SYSTEMS

8 th International Symposium on Tilapia in Aquaculture 2008 717 TILAPIA FEED AND FEEDING IN SEMI-INTENSIVE CULTURE SYSTEMS ABDEL-FATTAH M. EL-SAYED Oceanography Department, Faculty of Science, University of Alexandria, Alexandria, Egypt a_elsayed50@yahoo.com Abstract Semi-intensive farming of tilapia has been practiced for many years in different parts of the world, particularly in southeast Asia, either in monoculture or polyculture systems. Over the past two decades, semiintensive tilapia culture, with other herbivorous fishes such as carps has witnessed rapid expansion, particularly among small-scale farmers in Asia, Africa and Latin America. Therefore, over 90% of farmed tilapia are produced in semi-intensive systems (SIS). Natural food, produced through pond fertilization, is considered the driving vehicle of fish growth during early growth stages. Supplemental feeds must be added at later fattening stages. However, many farmers are now using pelleted feed as early as the 2 nd week after fish stocking. Moreover, little attention has been given to tilapia nutrition under SIS. This short review throws some light on tilapia feed and feeding in SIS with emphasis on the following practices: adoption of appropriate fertilization and supplemental feeding strategies, adoption of mixed-feeding schedules, reducing feeding rates and adoption of periphyton-based pond culture. Appropriate adoption of these practices would likely result in a substantial reduction in feed costs and significant economic improvement in pond outputs. INTRODUCTION Tilapia culture has been growing at an outstanding rate during the past two decades. As a result, the production of farmed tilapia has witness a 6-fold increase during the past 15 years, jumping from 383,654 mt in 1990 to 2,096,187 mt in 2005 (FAO, 2007). This has created a gap between seeds supplies and farmers demand, and an increasing demand for artificial feed as well. The prices of major feed ingredients; namely, fish meal (FM), soybean meal (SBM), corn and oils have been skyrocketing during the past few years. This has been attributed mainly to one or more of the following reasons: 1- declining production 2- increasing demands and competition among users. 3- The conversion of some ingredients to biofuel (e.g. corn to ethanol). Corn prices, for example, have sharply increased during the past few years, mainly because increasing demand for ethanol production is straining supplies. The amount of corn harvest used in the production of ethanol in the USA has jumped from only 6% in 2000, to about 20% in 2006. It is expected that ethanol production will

718 TILAPIA FEED AND FEEDING IN SEMI-INTENSIVE CULTURE SYSTEMS account for over 25% of corn production in 2007 (National Corn Growers Association,2008). In 2004, the production of moist corn grains in the US reached 300 million mt, representing 42% of world s 708 million mt. About 13% of the corn harvest in the US (about 39 million mt) was diverted to produce ethanol in 2004. Over 12 billion liters of corn ethanol was produced in the U.S. in 2004 (National Corn Growers Association) (http://www.ncga.com/ethanol/main/economics.htm). Since nutrition represents over 50% of total culture inputs, the major challenge facing tilapia culture industry is the production of cost effective and environmentally performing diets for farmed tilapia, using inexpensive, locally available ingredients. This simply means that searching for unconventional, cheap feed inputs for tilapia culture, together with the adoption of appropriate feeding strategies, is a must. Natural food versus supplemental feeding In developing countries, tilapia culture is practiced mainly, at small-scale levels, particularly in remote, rural areas, where culture inputs are scarce and fund assistance is limited. In the mean time, tilapia are generally produced for local consumption, where their gate prices are relatively low. Under these circumstances, it is unwise to use high quality commercial feed in small-scale farming systems. Instead, the adoption of both fertilization and supplemental feeding would be more appropriate and cost-effective (Diana et al., 1994; Green et al. (2002). It is also recommended that natural food should be used during early growth stages, whereas supplemental feeds must be added at later fattening stages. However, many farmers are now using pelleted feed as early as the 2 nd week after fish stocking (El-Sayed, 2007). In order to reduce feed cost in semi-intensive tilapia culture and to achieve sustainable and economic outputs in SIS, the following practices should be considered: 1- adoption of appropriate fertilization and supplemental feeding strategies. 2- adoption of mixed-feeding schedule practices. 3- reducing feeding rates. 4- Adoption of periphyton-based pond culture. Adoption of appropriate fertilization and supplemental feeding strategies As mentioned earlier, tilapia culture is practiced mainly at small-scale levels, particularly in rural areas, where culture inputs are scarce and fund assistance is limited. In the mean time, tilapia are generally produced for local consumption, where their gate prices are relatively low. Under these circumstances, the dependence on high quality commercial feed would not be necessary. Instead, the adoption of both fertilization and supplemental feeding would be more appropriate and cost-effective (Diana et al., 1994; Green et al., 2002). The adoption of both fertilization and supplemental feeding strategies in semi-

ABDEL-FATTAH M. EL-SAYED 719 intensive farming of tilapia has been practiced for many years in different parts of the world, particularly in Southeast Asia, and more recently in Africa and Latin America. In this system, farmed fish depend completely on natural food, produced through fertilization, during the early stages of their life, up to certain size, known as critical standing crop. Beyond this critical standing crop, fish growth will slow down, because natural food would be insufficient to meet their requirement. At this size, supplemental feed becomes necessary to sustain fish growth. Thus, providing supplemental feed at smaller fish size will lead to the waste of resources and increase in operating costs unnecessarily. Meanwhile, long delay in supplemental feeding will result in a reduction in fish growth and total yield. Therefore, selecting the proper timing and fish size for staring supplemental feeding is a key factor for successful semi intensive tilapia aquaculture. Depending on natural food during early stages of semi-intensive culture, and delaying feeding with commercial formulated feed or supplemental feed sources to latter stages, has been a common practice for small-scale farmers in many developing countries for decades. However, many other small pond fish farmers do not know that delaying supplemental feeding is more economic for them. Those farmers rarely adopt scheduled fertilization/ feed strategies. Instead, they fertilize and manage their systems by trial and error. In Egypt, for example, tilapia farmers generally use a single application of 1.5 3.0 mt/ha of dry poultry manure (and sometimes super phosphate and urea at rates of 35 and 25 kg/ha, respectively) before fish stocking. In addition, many farmers start feeding their fish with commercial feeds as early as 3 days after stocking, while few others start feeding about one month after stocking (El-Sayed, 2007, 2008). Several studies have considered the most suitable timing for supplemental feeding in semi-intensive tilapia culture The results of these studies are summarized in Table 1. Diana et al. (1996). found that the most efficient system for Nile tilapia reared semi-intensively is to grow the fish up to 100-150 g with fertilizers alone, followed by feeding them with supplemental feeds at 50% satiation. Feeding the fish before they reach this size was wasteful. These studies clearly indicated that delaying supplemental feeding in fertilized ponds sharply reduces feed cost without reducing fish yield. Therefore, small-scale tilapia farmers who adopt SIS must rely completely on fertilization as far as natural food supports fish growth during their early life stages, and must not use supplemental feed during these stages.

720 TILAPIA FEED AND FEEDING IN SEMI-INTENSIVE CULTURE SYSTEMS Table 1. Optimum feeding and fertilization regime in semi-intensive tilapia culture (from El-Sayed, 2008, International Aqua feed, 11 (1), 32-34. Fish species and size (g) All male Nile tilapia (15) All male Nile tilapia (23-24) All male Nile tilapia (0.1) Stocking density (fish m -2 ) Fertilization regime 3 urea (60 kg ha -1 week -1 + 34 kg TSP ha -1 week -1 ) 3 urea (60.7 kg ha -1 week -1 + 35.7 kg TSP ha -1 week -1 ) 4 Ammonia (28 kg ha -1 week -1 ) & ammonium phosphate and 5.6 kg ha -1 week -1 ) Optimum feeding timing When fish reach 100-150 g. 80 days after stocking 75 days after stocking Author Diana et al. (1996). Lin et al. (1997) Brown et al. (2000) Nile tilapia 3 Chicken litter (750 kg 42 days after Abdelghany (13.8), ha -1, biweekly), 100 stocking et al. (2002) common carp kg TSP + 20 kg urea (1.9) and silver ha -1 ) carp (10.7) Adoption of mixed-feeding schedules Mixed feeding schedules can be defined as "feeding the fish on a high protein diet alternatively with a low protein diet, over a predetermined period of time" (De Silva, 2007). The concept of "mixed feeding schedules" was first hypothesized by De Silva (1985), based on the observations on daily variations in protein and dry matter digestibility of feed in Asian chromid (Etroplus suratensis) and Nile tilapia (O. niloticus) (De Silva and Perera, 1983, 1984). In this hypothesis, the authors suggested that when the fish are provided a high protein diet throughout the rearing period, feed utilization efficiency could be reduced with time. This hypothesis was tested with Nile tilapia, through the use of mixed feeding schedules where a high protein diet (a diet containing the optimal protein requirement) was alternated with a low protein diet (containing about 10% less than the optimal requirement). The results indicated that the performance of fish maintained on mixed feeding schedules was comparable to, or even better, than, those fed regularly on a high protein diet. A number of experimental and field trials have been carried out on the adoption of mixed feeding schedules with a number of fish species (Nandeeesha et al., 1994, 1995, 2002; Hashim, 1994; Santiago and Laron, 2002; Patel and Yakupitiyage, 2003). Patel and Yakupitiyage (2003) compared the growth and feed efficiency of Nile tilapia

ABDEL-FATTAH M. EL-SAYED 721 reared semi-intensively on mixed feeding schedules using a 33% crude protein diet, alternatively with a relatively low protein content (22% crude protein) for 60 days. Mixed feeding schedule resulted in significant improvements in protein utilization efficiency compared to the continuously high protein diet, without any significant decline in growth rates. In fact, the mixed feeding schedule ensuring 2 days of the high protein diet followed by 3 days of low protein diet, performed the best. In a similar study, Santiago and Laron (2002) fed Nile tilapia fingerlings high protein (HP; 25%) or low protein (LP; 18%) diets at different feeding schedules. Weight gain was highest in fish fed the HP or LH for 23-days followed by LP for one day (2-3 HP-1LP). When the broodstock were fed HP (40%) or LP (25%), fry production was not affected by feeding schedules. However, when reproductive performance and economic evaluation were considered, broodstock on 1HP-1LP and 3HP-2LP gave the best overall performance. Reducing feeding rates Reducing feeding rates is another important factor affecting the economic return of tilapia in semi-intensive culture systems. Since natural food is the main energy input in fish ponds, excessive supplemental feeding may result in a considerable economic loss, in addition to a severe environmental impact, while partial reduction of feeding level may improve economic return. For example, Lin and Yi (2003) reported that Nile tilapia reared in fertilized ponds and fed supplemental diets at 50%, 75%, and 100% satiation, produced comparable yields, but the 50% level achieved considerable reduction in production costs and in nutrient loading. This means that farmers who adopt this feeding level can save about 50% of the feed without reducing their yield. Similarly, the highest production and net income of Nile tilapia polycultured with common carp and silver carp in fertilized ponds and fed 0, 1%, 3%, 5% biomass and to apparent satiation were achieved at 2.67% of fish biomass day -1 (equivalent to apparent satiation) (Abdelghany and Ahmad, 2002). It is clear, thus, that adoption of an optimal feeding regime will reduce both feed costs and nutrient loading in the ponds, and in turn, reduce environmental impacts of aquaculture practices. Adoption of periphyton-based pond culture Periphyton-based pond culture is a simple and cheap way of producing natural food in fish ponds for semi-intensively cultured fishes. In this system, woody branches, bamboo poles, or any other hard substrates are planted or fixed in shallow waters such as ponds, lagoons, reservoirs, etc., to enhance the growth of sessile autotrophic and heterotrophic aquatic biota such as bacteria, fungi, protozoa, phytoplankton, zooplankton, benthic organisms, etc., known as periphyton. This system has been successfully used for fish production (Azim et al., 2001, 2003, 2004; van Dam et al., 2002). Periphyton can partially or totally replace or complement supplemental feed in tilapia ponds, without reducing fish yield but with considerable reduction in production costs. Thus, periphyton-based aquaculture can be an excellent alternative to reduce

722 TILAPIA FEED AND FEEDING IN SEMI-INTENSIVE CULTURE SYSTEMS production costs and allow an economically viable tilapia production, particularly in rural, resource-limited regions in developing countries. REFERENCES 1. Abdelghany, A. E. and M. H. Ahmad. 2002. Effects of feeding rates on growth and production of Nile tilapia, common carp and silver carp polycultured in fertilized ponds. Aquacult. Res, 33:415-423. 2. Abdelghany, A. E., M. S. Ayyat and M. H. Ahmad. 2002. Appropriate timing of supplemental feeding for production of Nile tilapia, silver carp, and common carp in fertilized polyculture ponds. J. World Aquacult. Soc., 33: 307-315. 3. Azim, M. E., M. C. J. Verdegem, M. A. Wahab, A. A. van Dam and M. C. M. Beveridge. 2001. Periphyton boosts production in pond aquaculture systems. World Aquacult., 32 (4): 57-61. 4. Azim, M. E., M. C. J. Verdegem, I. Mantingh, A. A. van Dam and M. C. M. Beveridge. 2003. Ingestion and utilization of periphyton grown on artificial substrates by Nile tilapia Oreochromis niloticus L. Aquacult. Res., 34: 85-92. 5. Azim, M. E., M. M. Rahaman, M. A. Wahab, T. Asaeda, D. C. Little and M. C. J. Verdegem. 2004. Periphyton-based pond polyculture system: a bioeconomic comparison of on-farm and on-station trials. Aquaculture, 242: 381-396. 6. Brown, C.L., R. B. Bolivar, E. T. Jimenez and J. Szyper. 2000. Timing of the onset of supplemental feeding of Nile tilapia (Oreochromis niloticus) in ponds. In: Fitzsimmons, K. and Filho, J.C. (eds) Tilapia Culture in the 21 st Century. Proc. 5th Int. Symp. Tilapia Aquacult., American Tilapia Association and ICLARM, Rio de Janeiro, Brazil, pp. 237-240. 7. De Silva, S. S. 1985. Performance of Oreochromis niloticus (L.) fry maintained on mixed feeding schedules of different protein contents. Aquacult. Fish. Manag., 16: 621-633. 8. De Silva, S. S. 2007. Reducing feed costs through adoption of mixed feeding schedule practices in semi-intensive aquaculture. Int. Aqua Feed, 10(5): 18-22. 9. De Silva, S. S. and M. K. Perera. 1983. Digestibility of an aquatic macrophyte by the cichlid Etroplus suratensis with observations on the relative merits of three indigenous components as markers and daily changes in protein digestibility. J. Fish Biol., 23: 675-684. 10. De Silva, S. S. and M. K. Perera. 1984. Digestibility in Sarotherodon niloticus fry: effects of dietary protein level and salinity with further observations on variability in digestibility. Aquaculture, 38: 293-306. 11. Diana, J. S., C. K. Lin and K. Jaiyen. 1994. Supplemental feeding of tilapia in fertilized ponds. J. World Aquacult. Soc., 25: 497-506. 12. Diana, J. S., C. K. Lin and Y. Yi. 1996. Timing of supplemental feeding for tilapia

ABDEL-FATTAH M. EL-SAYED 723 production. J. World Aquacult. Soc., 27: 410-419. 13. El-Sayed, A.-F. M. 2007. Analysis of feeds and fertilizers for sustainable aquaculture development in Egypt. In M.R. Hasan (ed.) Study and analysis of feeds and fertilizers for sustainable aquaculture development. FAO Fisheries Technical Paper No. 497, Rome, FAO, pp. 401-422. 14. El-Sayed, A.-F. M. 2008. Reducing feed costs in semi-intensive tilapia culture. Int. Aqua feed, 11 (1): 32-34. 15. FAO (Food and Agriculture Organization of the United Nations). 2007. Fishstat Plus. FAO, Rome. 16. Green, B. W., Z. El Nagdy and H. Hebicha. 2002. Evaluation of Nile tilapia pond management strategies in Egypt. Aquacult. Res., 33: 1037-1048. 17. Hashim, R. 1994. The effect of mixed feeding schedules of varying dietary protein content on the growth performance of Channa striata fry. Asian Fish. Sci., 7: 149-155. 18. Lin, C. K. and Y. Yi. 2003. Minimizing environmental impacts of freshwater aquaculture and reuse of pond effluents and mud. Aquaculture, 226: 57-68. 19. Lin, C. K., Y. Yi and J. Diana. 1997. The effects of pond management strategies on nutrient budgets: Thailand. In: Fourteenth Annual Technical Report. Pond Dynamics/ Aquaculture CRSP, Oregon State University, Corvallis, Oregon, USA, pp. 19-24. 20. Nandeesha, M. C., S. S. De Silva, D. Krishna Murthy and K. Dathathri. 1994. Use of mixed feeding schedule in fish culture: field trials on catla, Catla catla (Hamlton- Buchanan), roho, Labeo rohita (Hamilton), and common carp, Cyprinus carpio L. Aquacult. Fish. Manag., 25: 659-670. 21. Nandeesha, M. C., S. S. De Silva and D. Krishna Murthy. 1995. Use of mixed feeding schedule in fish culture: Performance of common carp, Cyprinus carpio L. on plant and animal protein based diets. Aquacult. Res., 26: 161-166. 22. Nandeesha, M. C., B. Gangadhara and J. K. Manissery. 2002. Further studies on the use of mixed feeding schedule with plant- and animal- based diets for common carp, Cyprinus carpio (Linnaeus). Aquacult. Res., 33: 1157-1162. 23. Patel, A. B. and A. Yakupitiyage. 2003. Mixed feeding schedules in semi-intensive pond culture of Nile tilapia, Oreochromis niloticus L.: is it necessary to have two diets of differing protein contents?. Aquacult. Res., 44: 1343-1352. 24. Santiago, C. B. and M. A. Laron. 2002. Growth and fry production of Nile tilapia, Oreochromis niloticus (L.) on different feeding schedules. Aquacult. Res., 33: 129-136. 25. Van Dam, A. A., M. C. M. Beveridge, M. E. Azim and M. C. J. Verdegem. 2002. The potential of fish production based on periphyton. Rev. Fish Biol. Fish., 12: 1-31.