INTRODUCTION
Nile tilapia, (Oreochromis niloticus), constitute a major and important fish
in the Egyptian aquaculture, that's where tilapia production reached 557049
tons in 2011 and represents about 60.6% of the total production of fish farms
(GAFRD, 2012). This is due to the Nile tilapia is characterized by significant
economic characteristics: easily spawned, use a wide variety of natural and
artificial foods, resistance to diseases, tolerate poor water quality, grow rapidly
and produce a highly acceptable flesh for Egyptian consumers (El-Sayed,
2006;Abd Elaty,2012; Refaey, 2013 and Essa et al.,2013). Fish rearing and
feeding are of the most important factors in commercial fish farming because
feeding quality and regime may have consequences on both growth efficiency
and maintain the water quality in fish ponds (Lanari et al., 1995; and Ammar et
al., 2008).In recent years, processing techniques used to produce commercial
diets for use in aquaculture have widely increased. This increase has been
driven by the fast development of aquaculture, which has resulted in an
increased demand for high quality diets designed to meet nutritional
requirements of fish (Bud et al., 2009; Jafaryan et al., 2011).The processing
techniques including grinding, steam conditioning and extrusion are common in
the production of pellet diets in aquaculture and their use often facilitates
J. Adv. Agric. Res. (Fac. Agric. Saba Basha)
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Vol. 19 (1), 2014
improvement in the raw products. These diets have superior water stability,
better floating properties and a higher energy than pressed pelleted diets
(Guroy, 2006 and Ammar, 2008). Feed expense is the highest share of total
cost in any intensive aquaculture operations. Therefore, feed quality and
feeding strategy are of great importance in fish nutrition science. Therefore, the
present study aims to investigate the influence of feeding frequency and feed
forms (extruded and pressed pellets) on growth performance, nutrients
utilization and body chemical composition of monosex (male) Nile tilapia fry,
during nursing period.
MATERIALS AND METHODS
The present study was carried out at the Aquaculture Laboratory, El-Max
Research Station, National Institute of Oceanography and Fisheries, Alexandria
(NIOF) in order to evaluate the influence of feeding frequency and feed forms
(extruded and pressed pellets) on growth performance, nutrients utilization and
carcass composition of monosex (male) Nile tilapia fry, during nursing period.
Experimental System and animals: Eight glass aquaria with dimensions of
(30×70×40cm) were used .Each gives a water volume of 80 liters. Each
aquarium was supplied whit automatic heaters to maintain the water
temperature between 22:26°C, air pump and stone to provide continuous
aeration to water where water dissolved oxygen was 5.2 - 6.5 mg /L. Water pH
was in the range of 7.8 - 8.1 during the experimental period.
Feeding regime :Each diet was fed to randomly assigned duplicate aquaria
where each aquarium was stocked with 40 fry with an average 0.20g.Afixed
feeding regime 10 % of body weight per day (dry food /whole fish) was
employed and fish fed two or three times daily in equal proportions. Feeding
was performed for six consecutive days with no food being given on the
seventh day when the fish were weighed. The necessary adjustment in
quantity of food intake was carried out the end of every weighing period. Fish
were observed during the feed times.
Experimental diets: Two diets were formulated (pressed and extruded) were
purchased from NIOF research semi – commercial feed Milling EL Max
research station, Alex.
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Vol. 19 (1), 2014
Table 1. Composition (%), and chemical analysis (%) and gross energy of
the experimental diets
Ingredient Extruded diet Pressed diet
Fish meal (70% - Danish) 5.0 5.0
Fish meal (62% - Vietnam) 5.0 5.0
Soybean (45-solv VN) 36.0 36.0
Corn (9% CP) 12.0 12.0
Rice (polished) 10.0 10.0
Gluten (corn60%) 7.0 7.0
Wheat bran 10.0 10.0
Wheat (14 CP) 10.0 10.0
Corn/wheat starch 3.5 3.5
Dicalcium Phosphate 1.0 1.0
Vitamins and mineral 0.30 0.30
Fish oil 0.2 0.2
Chemical analysis (%)
Dry matter (DM) 93.95 93.4
Crud protein (CP) 32.11 32.10
Ether extract (E.E) 3.41 3.25
Ash 5.47 5.94
Crude fiber (CF) 2.99 2.82
Nitrogen free extract (NFE) 56.02 55.89
Gross energy(kcal/100g) (GE)* 444.44 442.34
P/E ratio (mg CP/kcal) 72.25 72.57
* GE= Gross energy based on 5.65 kcal/g for protein 9.45 kcal/g for Fat, 4.12 k
cal/g for Carbohydrate, Jauncey, K. and Ross B. (1982).
Analytical methods: An initial sample of fish, 2 per aquarium was killed prior
the start of the experiment and subjected to proximate analysis. A final sample
of 3 fry per aquarium was treated and fish diets similarly (AOAC, 1989 ).
Growth and nutrition of parameters measured:
1. Weight gain (WG)= final weight-initial weight
2. Specific growth rate (SGR % )
SGR = (Lnw2 – Lnw1) ×100 /t
Where w2 final mean weight of fish in grams
W1 initial mean weight of fish in grams
t Experimental period in days .
3. Food conversion ratio (FCR )
This was computed from the following.
FCR = Food consumed (g) / total wet weight gain
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Vol. 19 (1), 2014
4. Protein efficiency rates (PER)
PER = Total wet weight gain (g) / Amount of protein fed (g)
5. Protein productive value (PPV)
PPV (%) =( Retained protein (g) /protein intake (g) )×100
6. Energy gain (Kcal) (EG)
Energy gain = Et- E0
Where:
E0: energy content in fish carcass (Kcal) at the start
Et: energy content in fish carcass (Kcal) at the end
7. Energy utilization (EU %):
EU % = 100 × [(Et- E0)/ Energy intake (Kcal)]
Statistical analysis: Factorial analysis (2×2) of the experimental result was
conducted according to SPSS (version 16.00). Duncan's multiple range tests
Duncan's (1955) were carried out to test the significance level among means of
treatments.
RESULTS AND DISCUSSION
1-Chamical analysis of Experimental diets: The data of experimental diet
chemical analysis are presented in Table (1). Dry matter values were 93.95% in
extruded diet, while it was 93.4% in pressed diet. Concerning the crude protein
content, it was 32.11 and 32.10% in extruded and pressed diets, respectively.
Also ether extract% was higher in extruded diet (3.41) than in pressed diet
(3.25), while the Ash % was 2.99 and 2.82 in extruded and pressed diets,
respectively. Nitrogen free extract were 56.02% and 55.89% in extruded and
pressed diets, respectively.
2-Growth performance and survival rate: The Initial body weight (IBW), final
body weight (FBW), Body weight gain (BWG), Average daily gain(ADG),
Specific growth rate(SGR%/day), and survival of fish fed the experimental diets
are shown in Table (2). All groups had similar initial weight, but the final weights
among treatments were statistically different (P≤ 0.01).
Analysis of variance for the present results indicated that the fish fed
extruded diet had significantly higher body weight (5.08 and 4.89 g for three and
two times daily, respectively)compared to those fed on the pressed diet (3.47
and 3.15g for three and two times daily, respectively). Also the results showed
that FBW increased with increasing the feeding frequency in both extruded and
pressed diets. Significant differences were observed in BWG, ADG and SGR
due to the diet form and feeding frequency, where the highest values were
recorded in fish fed extruded diet three times/day (4.88 g, 0.061 g/day and 4.12
%/day, respectively) followed by fish fed on extruded diet two times/day (4.69g,
0.060 g/day and 4.02%, respectively). While, fish fed on pressed diet two times
/day had the lowest values (2.95g, 0.040 g/day and 3.48%, respectively).
These results showed that extruded diet and feeding three times/day
significantly improved the growth performance of monosex Nile tilapia fry during
the experimental period.
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Vol. 19 (1), 2014
Table 2. Influence of feeding frequency and two formed (extruded and
pressed) diets on growth performance and survival rate (%) of
monosex Nile Tilapia fry, during nursing period
Feed forms
Feeding
frequency
time/daily
Body weight Average
Initial
(g/fis)
Final
(g/fis)
Gain (g
fish/day)
ADG
(g/day)
SGR
(%/day)
Survival
rate
(%)
Extruded
2 0.20
±0.01
4.89
±0.60
4.69a
±0.59
0.060a
±0.01
4.02a
±0.13
83.75
±6.25
3 0.20
±0.01
5.08a
±0.62
4.88a
±0.61
0.061a
±0.01
4.12a
±0.11
84.10
±6.24
Pressed
2 0.20
±0.01
3.15b
±0.02
2.95c
±0.03
0.040b
±0.00
3.48b
±0.04
83.75
±1.25
3 0.20
±0.01
3.47b
±0.37
3.28b
±0.37
0.040b
±0.00
3.61b
±0.16
82.50
±5.00
*only means with different superscript letters are in each column
significantly different (P≤0.01)
These results are in accordance with those reported by Lee et al.(2000)
who reported that, a better growth and feed efficiency in 3.5 g flounder,
paralichthys olivaceus, fed to satiety was obtained at a feeding frequency of 2
or 3 times daily than once. Also, Ammar et al.(2008) showed that FBW of Nile
tilapia and mullet after 20 weeks were higher in fish fed extruded diet. Similar
results were also observed in other fish species by Ammar (2008) on sea bream
and sea bass and Aksnes et al. (1997) on sea bass, who observed that FBW
and SGR were significantly higher in fish fed extruded diet compared with fish,
fed the trash fish. Also, Aba et al.(2012) and Hematzade et al.(2013) showed
that rainbow trout fed on extruded diet had the best FBW, WG, and SGR in
compared with fish fed pressed diet. Wassef and Eisawy (1985); Aksnes et al.
(1997); Deguara (1997); showed that extruded diet of sea bream increased
significantly the body weight and growth rate .Guroy (2006) and Chebbaki
(2010) in their work on Dicentrarchus labrax, even with isoenergetic diets for
pressed and extruded diets have observed a better performance in terms of
weight when fish were fed extruded diets. Concerning the feeding frequency, in
their investigation on Nile tilapia, Sanches and Hayashi (2001) reported that
FBW increased with increasing the feeding times/day. Also, Yousif (2002)
observed that, minimum FBW recorded was in the 2 times/day feeding
frequency and the maximum was observed in fish fed 3 or 4 times/day.
Significant differences were not observed in final fish survival rates during the
feeding period with two diets and two feeding frequencies (values were ranged
from82.50% to 84.75%, Table 2), although a highest survival rate (84.75%) was
obtained at a Nile tilapia fry fed extruded diet three times daily. These results
J. Adv. Agric. Res. (Fac. Agric. Saba Basha)
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Vol. 19 (1), 2014
are in agreement with Sanches and Hayashi (2001) who found that Nile tilapia
fry survival rate was not significantly affected by feeding frequency.
1- Nutrients utilization
Results of feed intake (FI), feed conversion ratio (FCR), Protein Efficiency
ratio (PER), Protein productive value (PPV), Energy gain (EG) and Energy
utilization (EU) are presented in Table (3). These values were influenced by
different form diets and feeding frequency, while the pressed diet and two daily
feeding frequencies provided lower values compared with the extruded diet and
three times daily feeding frequency. Concerning FI and FCR, the fish fed
extruded diet at two and three times daily presented a significantly (P ≤0.01)
higher feed intake (FI) (10.84 and 11.38g/fish, respectively) than those fed
pressed diet at two and three times daily (7.60±0.22 and 8.45±0.17g/ fish,
respectively). FCR did not reveal significant differences in terms of feeding
regime, although Nile tilapia fry fed extruded diet at three times daily used less
feed (2.33) to produced one unit of weight gain. The techniques of processing
may have effect on feed consumption as well as digestibility of the feed content.
Feed consumption was clearly affected by diet processing as the best FCR was
found in fish fed the extruded pellet. Fish fed the floating extruded diet
consumed significantly less (P ≤0.01) on a biomass basis than fish fed the
pressed pellet. These results similar to those observed by Ammar (2008) who
reported that the best FCR was obtained by fish fed extruded diet. Also, similar
trends were obtained by some authors on different fish species, Ammar et
al.(2008) on Sea Bass and Sea Bream, Aba et al.(2012) and Hematzade et
al.(2013) on rainbow trout.
As a consequence of these growth results, PPV was significantly (P ≤0.01)
higher in fish fed extruded diet three and two times daily (25.23and 22.94%,
respectively) than those in fish fed pressed diet three and two times /day(22.76
and 19.42, respectively). Also, in case of the feeding frequency, the fish fed
three times daily showed significant enhancement in PPV than fish fed two
times daily. The best PER were obtained from the fish fed on extruded diet with
feeding frequency three times daily (1.37 and 1.35, respectively) but there was
no significant differences compared with the other treatments. These findings
are in agreement with the findings of Venou et al. (2003), who reported that
extrusion improved significantly all apparent digestibility coefficients, and
Andrew et al. (2004) who reported that softer pellets increased consumption
and reduced waste from handling.
Similar trend was observed in the results of EG and EU which were
significantly higher in fish fed extruded diet (6.90and 6.00Kcal for EG and
14.01and 12.51% for EU, respectively) compared with fish fed on pressed diet
(4.47and 3.53Kcal for EG and 12.00and 10.52% for EU, respectively).
J. Adv. Agric. Res. (Fac. Agric. Saba Basha)
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Vol. 19 (1), 2014
Table 3. Influence of feeding frequency and two formed (extruded and
pressed diets) on feed utilization parameters of monosex Nile
Tilapia fry during nursing period
*Only means with different superscript letters in each column are
significantly different (P≤0.01)
2- Whole body chemical composition
Whole-body proximate composition of the mono sex Nile tilapia fingerlings
are given in Table 4. No significant (P ≤0.01) differences in any of the proximate
components were detected. However, crude protein and ether extract of wholebody
fish fed extruded diets three times daily (68.90and 13.29%, respectively)
was the highest value compared with the other treatments. On the other hand,
the highest ash content was presented by fish fed on pressed diet two times
daily (22.4%).According to the present results in Table (4), feeding Nile tilapia
fry 3 times daily with extruded diet improved whole Body composition in
fingerlings by increasing the protein content and reduce the ratios of fat and
ash. Same trend was observed by Aba et al.(2012) when they found that
rainbow trout bodies which fed on extruded diet had more protein, more fat and
less moisture, also, Noesk-Hallin et al. (1985)reported that feeding at some
times of day conductive to lean body growth and at other times to fattening.
Feed
forms
Feeding
frequency
time/daily
Feed
intake
(g/fish)
FCR PER PPV (%)
Energy
Gain
(kcal)
Energy
Utilization
(%)
Extruded
2 10.84b
±1.01
2.34
±0.01
1.35a
±0.00
22.94b
±0.21
6.00a
±0.40 12.51b ±0.33
3 11.38a
±1.04
2.33
±0.01
1.37a
±0.01
25.23 a
±0.32
6.90a
±0.51 14.01±0.31
Pressed
2 7.60c
±0.22
2.59
±0.09
1.21b
±0.04
19.42c
±0.78
3.53c
±0.01 10.52c±0.26
3 8.45c
±0.17
2.57
±0.15
1.21b
±0.07
22.76b
±1.72
4.47b
±0.11 12.00b±0.53
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Table 4. Influence of feeding frequency and two formed (extruded and
pressed diets) on whole body chemical composition parameters
of monosex Nile Tilapia fry, during nursing period
Feed
forms
Feeding
frequency
time/daily
Dry
matter
(%)
% On dry matter basis Carcass
energy
(kcal/100
g)
Crude
protein
Ether
extract Ash
Extruded
2 25.95
±0.38 65.06 ±0.61 13.16±1.04 21.78±0.17 491.18
±3.47
3 26.11
±0.36 68.90±0.58 13.29±0.89 17.81±0.20 563.03
±3.51
Pressed
2 24.47
±0.38 64.88±0.62 12.71±1.22 22.41±2.09 485.92
±11.61
3 24.63
±0.21 66.09±7.39 13.13±0.29 11.06±12.39 551.51
±48.63
* Only means with different superscript letters are significantly different
(P≤0.01)
CONCLUSION
From the results of the present study we can concluded that ,the
manufacturing and processing technique has significant (P ≤0.01)influence on
the growth, feed utilization and whole Body composition parameters of monosex
Nile Tilapia. The present rearing and feeding trial demonstrated that monosex
Nile tilapia fry during nursing period fed an extruded diet and 3 times daily
yielded a better growth performance, survival rate, feed efficiency and flash
quality compared to fish fed the pressed pelleted diet 2 or 3 times daily.
Acknowledgement:
The authors gratefully acknowledge all staff of fish breeding and rearing
lab, NIOF; Alexandria, for their help and supporting during the experiment
period. In addition, we would like to thank Mr. Abd Elbaeth Abd Elaty for his
understanding and providing the Possibilities and tools needed to make a part
of this experiment in his own fish farm.
