8th 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 2nd 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
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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 2nd 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.
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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
Stocking
and size (g)
density
Fertilization regime
Optimum
Author
feeding timing
(fish m-2 )
urea (60 kg ha-1
When fish
Diana et al.
week-1 + 34 kg TSP
reach 100-
(1996).
ha week )
150 g.
urea (60.7 kg ha-1
80 days after
Lin et al..
stocking
(1997)
Ammonia (28 kg ha-1
75 days after
Brown et al..
week-1) & ammonium
stocking
(2000)
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
All male Nile
3
tilapia (15)
-1
All male Nile
3
-1
-1
tilapia (23-24)
week + 35.7 kg TSP
ha-1 week-1)
All male Nile
4
tilapia (0.1)
phosphate and 5.6 kg
ha-1 week-1)
Nile tilapia
(1.9) and silver
3
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
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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.
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