Maize (called vutta in Bengali) is one of the emerging crops in Bangladesh, is being cultivated for long time; though still is being considered as minor crops. Price, demand and supply of maize are increasing worldwide. Bangladesh has a great potentiality to increase the maize cultivation due to its soil and climate suitability. Due to the huge demand for poultry feed, people and government of Bangladesh paid attention to grow it. It is also a promising fish feed ingredient, which is frequently used as fish feed in small scale fish farmer (Dongmeza et al., 2010). It has been used successfully as energy sources in the diet many carnivorous fish (Pfeffer et al., 1991, Bergot, 1993, Hemre et al., 1996, Sanden et al., 2006). It is notable that protein, mainly used for growth, is the main expensive macro-ingredient in fish feed. But if there is no available energy in the diet; growth of fish is compromised. When carbohydrate is available in the fish feed, it is used as energy sources, and more protein is used for growth, which is commonly known as protein sparing effect. Thus, maize is a one kind of carbohydrate (starch) can be useful energy sources in fish diet.
Digestibility energy is one of the important concern to use any ingredient in fish feed, depends on origin, sources, physical state, inclusion level of starch and fish species. There are three varieties of maize, has been used in fish feed, such as
- Normal maize: contains 28-30% of amylose and 70-72% of amylopectin,
- Amlylomaize: contain 65% amylose and
- Waxymaize : contains 1% amylose and 99% amylopectin.
High proportion of amylose has a negative effect on starch digestibility in fish (Bergot, 1993). In presence of crystalline structure of amylose and amylopectin, starches are categorised in to three groups (A, B and C) (Gallant et al., 1992). Maize starch is in group B (Stone, 2003). Apparent digestibility coefficient of three varieties of maize was compared in carnivorous fish, rainbow trout diet and found that ordinary maize was intermediate (33%) between amylomaize (18%) and waxymaize (54%) (Bergot, 1993). It is noted that most of the aquaculture fish species in Bangladesh, are omnivorous or herbivorous; they are more capable of digesting carbohydrate than carnivorous. Trout has a intermediate capability to digest starch compare to fish with high digestibility of starch such as grass carp, common carp or tilapia and fish with lower digestibility of starch such as cod or sea bass (Bergot, 1993).
Processing (gelatinisation or extrusion) improves the digestibility of any kind of starch (Bergot, 1993, Stone, 2003, Krogdahl et al., 2005). Since treated starch, including maize digestibility coefficient reached to 95% while that of non-treated starched remained below 60% in the diet of rainbow trout (Bergot, 1993). Digestibility of raw starch is lower than that of gelatinized starch (Yamamoto et al., 2007). Gelatinization has a positive effect on starch digestibility and growth in rainbow trout (Bergot and Breque, 1983). Gelatinised maize starch in the diet of channel cat fish was 17% more digestible than native maize starch (Lovell, 1989).
Inclusion level of maize in fish feed diet should be estimated to determine the proper nutritive balance of diet. In Tilapia fed diet containing maize starch from 22% to 46% showed significantly higher weight gain, specific growth rate, feed efficiency ratio and protein efficiency ratio (Pérez-Jiménez et al., 2007). The hepatosomatic index (HSI) was increased linearly with increasing level of maize due to enlargement liver by storage of glycogen (Wu et al., 2007). In most species liver glycogen is generally used as a first reserved energy sources during starvation, then lipid reserves are used to obtain energy, when both are depleted protein from skeletal muscle is catabolised for energy (Pérez-Jiménez et al., 2007).
Moreover, maize leaves and cob can be used as feed source for herbivorous fish such grass carp. Maize cob is being used for feeding grass carp traditionally in some region of Bangladesh. Research can be done to use maize cob and leaf in fish feed especially, grass carp, silver barb (Thai Sarputi) and tilapia. In Vietnam, maize leaves are using as a feed ingredient for grass carp and research revealed that fresh maize have a good potential to be used as supplement in the diets for grass carp (Dongmeza et al., 2010)
However, price of fish meal (protein sources for fish feed) and fish oil are increasing sharply in the world. Fish nutritionist are trying to find any alternative sources of energy for fish especially from carbohydrate, because carbohydrate are still cheap and readily available energy compare to protein and lipid. Research need to be undertaken with across the fish species, cultured in Bangladesh to minimize the level of inclusion of maize starch in fish feed to obtained better growth. It will contribute to reduce the feed cost for fish farm as well as improve the market of maize and strengthen the economy of Bangladesh.
- Bergot, F. 1993. Digestibility of natives starches of various botanical origins by rainbow trout (Oncorhynchus mykiss). (In: S.J. Kaushik and P. Luquet, Editors, Fish Nutrition in Practice.) Proceedings of the IVth International Symposium on Fish Nutrition and Feeding, 24 June-27 June 1991, Biarritz (France), INRA Editions, Paris (1993), pp. 857–865.
- Bergot, F. Breque, J. 1983. Digestibility of starch by rainbow trout: Effects of the physical state of starch and of the intake level. Aquaculture, 34, 203-212.
- Dongmeza, E. B., Francis, G., Steinbronn, S., Focken, U. Becker, K. 2010. Investigations on the digestibility and metabolizability of the major nutrients and energy of maize leaves and barnyard grass in grass carp (Ctenopharyngodon idella). Aquacult. Nutr., 16, 313-326.
- Gallant, D. J., Bouchet B, Buléon A Pérez, S. 1992. Physical characteristics of starch granules and susceptibility to enzymatic degradation. Eur J Clin Nutr. 1992 Oct;46 Suppl 2:S3-16., 46 (suppl. 2), S3-S16.
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- Krogdahl, Å., Hemre, G.-I. Mommsen, T. P. 2005. Carbohydrates in fish nutrition: digestion and absorption in postlarval stages. Aquaculture Nutrition, 11, 103-122.
- Lovell, T. 1989. Re-evaluation of carbohydrates in fish feeds. . Aquaculture Magazine, 15, 62-64.
- Pérez-Jiménez, A., Guedes, M. J., Morales, A. E. Oliva-Teles, A. 2007. Metabolic responses to short starvation and refeeding in Dicentrarchus labrax. Effect of dietary composition. Aquaculture, 265, 325-335.
- Pfeffer, E., Beckmann-Toussaint, J., Henrichfreise, B. Jansen, H. D. 1991. Effect of extrusion on efficiency of utilization of maize starch by rainbow trout (Oncorhynchus mykiss). Aquaculture, 96, 293-303.
- Sanden, M., Krogdahl, Å., Bakke-Mckellep, A. M., Buddington, R. K. Hemre, G.-I. 2006. Growth performance and organ development in Atlantic salmon,Salmo salar L. parr fed genetically modified (GM) soybean and maize. Aquacult. Nutr., 12, 1-14.
- Stone, D. A. J. 2003. Dietary carbophydrate utilization by fish. Reviews in Fisheries Science, 11(4), 337-369.
- Wu, X.-Y., Liu, Y.-J., Tian, L.-X., Mai, K.-S., Yang, H.-J. Liang, G.-Y. 2007. Effects of raw corn starch levels on growth, feed utilization, plasma chemical indices and enzyme activities in juvenile yellowfin seabream Sparus latus Houttuyn. Aquaculture Research, 38, 1330-1338.
- Yamamoto, T., Shima, T., Furuita, H., Sugita, T. Suzuki, N. 2007. Effects of feeding time, water temperature, feeding frequency and dietary composition on apparent nutrient digestibility in rainbow trout Oncorhynchus mykiss and common carp Cyprinus carpio. Fish. Sci., 73, 161-170.
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