Effect of dietary supplementation of betaine and/or stocking density on performance of nile tilapia
In the present work, feeding O. niloticus fish on diets containing different levels of betaine (0.0, 0.5 and 1.0%) and stocked at three densities (2, 3 and 4 g fish/liter) led to some results which could be summarized in the following points.
The results clearly showed that the diets containing (1% and 0.5% betaine) were slightly better in all the tested parameters than the control, but on the other hand the results clearly showed that the fish stocked at 2g fish/l and 3g fish/l were slightly better in average weight gain, average daily gain, specific growth rate, relative growth rate, and survival rate than the control.
Increasing dietary betaine level caused significant increases in the growth rates (RGR and SGR) and consumption of feed and protein, but feed conversion efficiency decreased significantly.
Elevated stocking density of fish led to significantly lower growth rates and protein intake; yet, the feed conversion improved significantly.
Dietary protein utilization (PER and PPV) was improved significantly by raising the dietary betaine level, but the survival rate was not affected. Raising the stocking density of the experimented fish resulted in significant decreases of dietary protein utilization, although the survival rate was not influenced.
Concerning whole fish body composition, percentages of DM and CP (and to some extent also ash) increased, but EE% decreased by elevating the betaine level. Increasing stocking rate of fish was responsible for increased % of DM, leading to increases in CP and ash, but EE percentages of the whole fish body decreased.
Elevating dietary betaine level led to increasing feed intake and feed cost, but increasing fish weight gain compensated this input items, so led to lower feeding costs for producing one-kilogram fish weight gain. This means that dietary inclusion of betaine improves pisciculture economy. From the foregoing results it could be concluded that the addition of 1.0% of betaine in the diets of Nile tilapia stocked at 2g fish/l is useful to enhance the fish growth and production economy.
INTRODUCTION
Nile tilapia O. niloticus, are considered as the most common and popular fish in Egypt, and has proved to be of great importance. However, Khouraiba (1997) reported that tilapias are constantly gaining importance in aquaculture, especially in the tropics and subtropics. In Egypt, tilapias constitute approximately 45% of inland water fishery production.
Nutrition is the most important factor of the culture process; it is often represent the major operating cost of aquaculture. It is advisable for aquaculturist to know the optimum quality and quantity of feeds introduced to fish to avoid poor growth, health and reproduction (Landau, 1992). Deficiency of some of these components causes a depression in growth of fish and may lead to diseases (Magouz, 1990).
Optimal feeding regimes may result in reduced feed costs by minimizing expenditure of metabolic rate of fish. Attractive feed may be consumed quickly, thus reducing losses by leaching of essential water-soluble components. An addition of chemo-attractants to pelletized feeds may increase ingestion rates and improve growth, survival and food conversion (El-Sayed et al., 2005).
Individual amino acids and betaine are the most effective feeding stimulants in various crustaceans’ feeds. Betaine is also a flavor additive in diets or rearing water of some crustaceans and fish species. It is a naturally occurring substance found in a wide variety of plant and animal species. The osmo - protective properties of betaine are based on its ability to increase intracellular osmotic strength, to replace inorganic ions in this function and protect enzymes from osmotic inactivation. It also reduces mortality and enhances growth performance.
Betaine is an oxidized form of choline (a vitamin like nutrient), which is an important component of the phospholipid lecithin and certain other complex lipids. Choline serves as a source of labile methyl groups for the synthesis of various methiolated metabolites and as a precursor of acetylcholine. There may be an interaction between dietary choline, betaine and essential amino acid methionine. It appears that betaine spares the choline requirements in juvenile fish (Kasper et al., 2002 and Magouz, 2002a).
Stocking density affects the yield form of an aquaculture site. Since increasing stocking density increase problems with water quality and yield of fish (Khouraiba, 1989). On the other hand, optimum returns on capital and labor depended upon using the highest possible stocking densities which are consistent with good survival and growth.
The objective of this study was to determine if betaine is a flavor additive in tilapia diets and to investigate its effects on growth performance and reducing environmental stress in semi-intensive production system of tilapia fingerlings.
MATERIALS AND METHODS
The present works was carried out at the wet lab of the Department of Animal and Fish Production, Faculty of Agriculture, Kafr El-Sheikh University during year 2005. Feeding experiment was conducted to study the effect of dietary graded levels of betaine on growth performance, carcass composition and feed utilization of Nile tilapia, Oreochromios niloticus, fingerlings for 15 weeks at 3 stocking densities. The experimental system consisted of 27 glass aquaria (60×35×40cm), each aquarium was continuously supplied with a compressed air from an electric compressor. Dechlorinated tap water was used to change one third of the water in each aquarium every day. Water was aerated before be used for about 24 hours to remove chlorine.
Experimental fish:
A group of Nile tilapia (O. niloticus) with an average initial body weigh of about 20g was stocked at three densities, being 2, 3 and 4 g fish / liter. Fish were obtained from the stock of earthen ponds (from a private farm in Hamoul, Kafr El-Sheikh Governorate) and transported into the aquaria located at the fish researchs laboratory of Faculty of Agriculture, Kafr El-Sheikh Governorate. The fish were maintained in these aquaria for 2 weeks before the beginning of the experiment for the acclimatization purpose. The fish were fed during the acclimatization period on a basal diet at a daily rate of 3% of the body weight, at 2 times daily. The experimental treatments were tested at three aquaria (replicates) for each.
Experimental diet:
A basal diet (28% crude protein) was formulated from the memorial ingredients (fish meal, soybean meal, yellow corn, wheat bran, sunflower oil, vit. & min. and betaine). Betafin® (betaine) was bought from the local distributor of the product produced by Dansico Animal Nut., Finland. However, the ingredients of the experimental diet were bought from the local market. These ingredients were pressed by manufacturing machine (pellets size was 3 mm). The basal diet No.1 was considered as a control. Composition and chemical analysis of the basal and experimental diets are presented in Table (1).
Table (1): Composition (%) and chemical analysis (% dry matter bases) of the experimental diets.
|
Ingredients |
Diet No. 1 % | Diet No. 2 % | Diet No. 3 % |
|
Fish meal |
10 |
10 |
10 |
|
Soybean meal |
40 |
40 |
40 |
|
Yellow corn |
32.7 |
32.2 |
31.7 |
|
Wheat bran |
10 |
10 |
10 |
|
Sunflower oil |
5 |
5 |
5 |
|
Dicalcium phosphate |
2 |
2 |
2 |
|
Vitamins & minerals* |
0.3 |
0.3 |
0.3 |
|
Betaine |
0.0 |
0.5 |
1.0 |
| Chemical analysis | |||
|
Dry matter (DM) |
89.56 |
89.42 |
89.33 |
|
Crude protein (CP) |
28.27 |
28.06 |
27.81 |
|
Ether extract (EE) |
4.91 |
4.31 |
4.66 |
|
Ash |
6.79 |
6.82 |
6.40 |
|
Crude fiber (CF) |
4.27 |
4.16 |
4.12 |
|
Nitrogen free extract (NFE) |
55.76 |
54.17 |
57.01 |
|
GE ** |
435 |
420 |
435 |
|
Protein/energy (P/E) ratio (mg CP/kcal GE) |
64.99 |
66.81 |
63.93 |
|
ME *** |
389 |
375 |
391 |
* Composition of the vitamins and minerals mixture (calculated for each kg of the mixture) in the diet is: Vitamins A, D3, E, K3, B1, B2, B6, B12, C, Biotin, Folic acid, and Pantothenic acid, being 5.714.286 IU, 85.714 IU, 7.143 mg, 1.429 mg, 571 mg, 343 mg, 571 mg, 7.143 ug, 857 ug, 2.857 mg, 86 mg, and 1.143 mg, respectively; Minerals: Phosphorus, 28.571 mg; Manganese, 68.571 mg; Zinc, 51.429 mg; Iron, 34.286 mg; Copper, 5.714 mg; Cobalt, 229 mg; Selenium, 286 mg, and Iodine, 114 mg; and Inert essential agent: Starch, 57 g; Natural H, 29 g; and CaCo3 1000 g.
**GE (Gross energy, kcal / 100g DM) = CP x 5.64 + EE x 9.44 + NFE x 4.11 (according to MacDonald et al., 1973).
***ME (Metabolizable energy, kcal / 100g DM) was calculated by using factors 3.49, 8.1 and 4.5 kcal/g for carbohydrates, fat and protein, respectively (according to Pantha , 1982).
Experimental procedure:
The experiment continued for 15 weeks. During the experimental period the fish were fed the experimental diets at a rate of 3% of the live body weight daily. The diet was introduced twice daily, at 8 a.m. and 2 p.m. The amount of feed was adjusted weekly based on the actual body weight changes. Samples of water were taken daily before changes the water and after adding the diets weekly from each aquarium to determine water quality parameters. Light was controlled by a timer to provide a 14h light: 10h dark as a daily photoperiod.
Analytical methods:
Samples of water from each aquarium were taken to determine the water temperature, pH value, dissolved oxygen, alkalinity, hardness, NO2 and NH3 concentrations (according to Abdelhamid, 1996). Water temperature as degree centigrade was recorded every day by using a thermometer. The pH value of water was measured daily using an electric digital pH meter (Jenway Ltd, model 350-pH meter). Dissolved oxygen concentration was determined weekly using an oxygen meter (model d-5509). The NO2 and NH3 concentrations were determined by using the commercial kits supplied by Diamond, Diagnostic, Egypt. Determination of DM, CP, EE, CF and ash in the basal diet and in fish body at the start and at the end of the experiment for different groups were carried out according to the methods of A.O.A.C. (1990). At the end of the experiment, three fish were derived from each group for drying at 60ºC for 48 hours and then milled through electrical mill and kept at 4oC until analysis.
Growth performance and efficiency of feed and protein utilization:
The growth performance and feed utilization parameters were calculated according to the following equations: Average weight gain (AWG) = average final weight (g) - average initial weight (g), Average daily gain (ADG) = average final weight (g) - average initial weight (g) Time (days), Survival rate (SR%) = total number of fish at the end of the experiment × 100 / total number of fish at the start of the experiment, Relative growth rate (RGR) = average weight gain (g) / average initial weight (g), and Specific growth rate (SGR, % = 100 [ln wt1- ln wto/T] here ln = Natural log., Wto = Initial weight (g), Wt1 = Final weight (g), and T = time in days. However, Feed conversion ratio (FCR) = total feed consumption (g) Weight gain (g), Protein efficiency ratio (PER) = body weight gain (g) / protein intake (g), Protein productive value (PPV%) = 100 [retained protein (g) / protein intake], and Energy retention (ER%) = 100 [retained energy (Kcal) energy intake (Kcal), according to Abdelhamid (2003).
Statistical analysis:
The data collected were statistically analyzed by using general linear models procedure adapted by SAS (1996) for users guide. Means were statistically compared using Duncan's multiple range test (Duncan, 1955).
RESULTS AND DISCUSSION
Water quality parameters:
The physico-chemical parameters of tap water used in this experiment are shown in Table (2). Data showed that all tested water quality criteria were suitable for rearing Nile tilapia fingerlings as cited by Abd El-Hakim et al. (2002) and Abdelhamid (2003). Also, Abdelhamid et al. (2002) found that similar values were suitable for rearing Nile tilapia. In the same trend, Abdelhamid et al. (2004 b&c) tested water quality criteria and reported similar values which were suitable for rearing Nile tilapia fish However, the ranges of the tested water criteria were 25.5 – 26.5 o C, 7.2 – 7.9 pH , 4.3 – 6.7 mg/l DO, 0.5 – 0.9 mg/l total ammonia and 0.25 – 0.46 mg/l NO 2. Thus, Abd El-Hakim et al . (2002) cited the suitable values of water quality parameters for pisciculture as > 5 mg/l DO, and pH 6.7 – 8.6. Also, Abdelhamid (2003) cited the water quality criteria which are suitable for aquaculture in fresh water as pH 6.5 – 9.0, DO > 5 mg/l and NH < 0.02 mg/l.
Growth performance:
Data of growth performance parameters as affected by level of betaine addition and/or stocking density of Nile tilapia fingerlings are illustrated in Table 3. The analysis of variance cleared that there were no significant (p ≥ 0.05) differences in the initial weight (IW) of the fish, but there were significant differences in the final weight (FW), weight gain (WG) and average daily gain (ADG) due to betaine levels (B) in the diet, stocking density (SD) of the fish as well as in their interaction (B x SD). Increasing the dietary level of betaine addition led to higher (P ≤ 0.05) FW, WG and ADG, whereas the opposite was true concerning the stocking density, since increasing SD of the fish caused lower (P ≤ 0.05) FW , WG and ADG. So , the best performance criteria were reported for the highest betaine level (1%) at the lowest stocking density (2g fish/l) which had FW 54.31 g/fish and gained in weight 34.13 g/fish as well as realized ADG of 0.32 g/fish throughout the whole experimental period of 105 days in glass aquaria under the indoor (wet lab) experimental conditions. Similar positive effect of dietary betaine inclusion on fish performance was reported by Magouz (2002b) using 4 g betaine/kg diet of tilapia in glass aquaria and by Abdelhamid et al. (2004a) using 2 kg betaine/ton diet of un-sexed Nile tilapia in earthen ponds, but not by Abdelhamid and Ibrahim (2003) using 2 g betaine/kg diet for mono sex Nile tilapia in earthen ponds. Also, Bakeer and Mostafa (2006) revealed that dietary incorporation of betaine (2Kg/Ton) increased (insignificantly) all growth performance parameters of Nile tilapia in cold season. Yet, similar negative effect of increasing stocking density on fish performance was found by El-Saidy and Gaber (2002b).
Table (2): Ranges of some important measured physico-chemical parameters of water quality.
|
Water parameters |
Treatments | |||||
|
B (%) |
SD (g fish / l) | |||||
|
0 |
0.5 |
1 |
2 |
3 |
4 | |
|
Temperatue (º C) |
25.8-26.4 |
25.7-26.5 |
25.5-26.4 |
25.8-26.4 |
25.7-26.5 |
25.5-26.4 |
|
The pH value |
7.3-7.9 |
7.2-7.9 |
7.3-7.9 |
7.3-7.9 |
7.2-7.9 |
7.3-7.9 |
|
DO (mg/l) |
5.0-5.9 |
4.3-5.9 |
4.5-6.7 |
5.0-5.9 |
4.3-5.9 |
4.5-6.7 |
|
Total ammonia (mg/l) |
0.6-0.9 |
0.6-0.9 |
0.5-0.9 |
0.6-0.9 |
0.6-0.9 |
0.5-0.9 |
|
NO2 (mg/l) |
0.25-0.46 |
0.26-0.44 |
0.29-0.43 |
0.25-0.46 |
0.26-0.44 |
0.29-0.43 |
B = Betaine
SD =Stocking density.
Table (3): Effect of different betaine levels and density rates on growth performance parameters of Nile tilapia (means* ± SE).
| Treatment |
I W, g/fish |
FW, g/fish |
WG, g/fish |
ADG, g/fish | |
|
Betaine Level | |||||
|
0 % |
20.06±0.01 |
40.25±0.82c |
20.19±0.87c |
0.19±0.00c | |
|
Stocking Rate |
20.17±0.03 |
48.37±1.60a |
28.20±1.58a |
0.26±0.41a | |
|
2 g fish /l | |||||
|
Interaction |
|
|
|
| |
|
Betaine |
Stocking |
20.08±0.03 |
43.35±0.05a |
23.27±0.02a |
0.22±0.00a |
|
|
| ||||
|
0.5 % |
2 g fish /l |
20.24±0.05 |
47.45±0.34a |
27.21±0.01a |
0.26±0.00a |
|
1% |
2 g fish /l |
20.19±0.04 |
54.31±0.09a |
34.12±0.12a |
0.32±0.00a |
*Means (in the same column) superscripted with different letters significantly (P≤0.05) differ.
Growth rates and feed utilization:
Data of relative growth rate (RGR), specific growth rate (RGR), feed intake, feed conversion ratio (FCR) and protein intake are given in Table 4 as means ± standerdard errors. Both variables studied and their interaction affected significantly (P≤0.05) all these above-mentioned parameters. Since increasing the dietary betaine levels led to significant increases in RGR, SGR and feed and protein intakes but reduced the feed conversion efficiency. The opposite trend was recorded with increasing the stocking density of the fish, where all the tested traits were lower, except FCR was better significantly. The best results were obtained from the treatment group fed the 1% betaine supplemented diet and stocked at 2 g fish/l for RGR , SGR and feed and protein intakes ; but concerning the FCR , the best treatment was that fed the no – betaine supplemented diet and stocked at 4g fish/l .
These results agree with those found by Vieira et al. (2001) who reported significant differences for body weight gain and FCR in Nile tilapia fish fed betaine supplemented diets. Since betaine increases feed intake (Kasper et al., 2002). Magouz (2002b) gave better (P≤0.05) SGR and FCR by betaine inclusion (2-8 g kg diet) in Nile tilapia diet (in glass aquaria.) Abdelhamid et al. (2004a) working on Nile tilapia in earthen ponds, reported better weight gain, RGR, SGR, but lower feed conversion by betaine including diets (1-2 kg/ton). Moreover, Bakeer and Mostafa (2006) revealed that betaine dietary inclusion significantly improved FCR. Similar negative effects of increased crowding were reported by El-Saidy and Gaber (2002b) on Nile tilapia feed utilization. Since crowding stress negatively affected the physiological functions of Nile tilapia (Abdel-Tawwab et al., 2005).
Table (4): Means* ± SE of growth rates and feed and nutrient utilization of Nile tilapia fed the experimental diets containing different levels of betaine and three stocking rates.
|
Treatment |
RGR |
SGR |
Feed Intake g/fish |
FCR |
Protein | |
|
Betaine Level | ||||||
|
0 % |
1.07±0.06c |
0.66±0.04c |
40.25±0.27c |
1.99±0.06c |
2.88±0.02c | |
| Stocking Rate |
1.39±0.13a |
0.83±0.07a |
48.37±0.53a |
1.71±0.05a |
3.38±0.11a | |
|
2 g fish/l | ||||||
|
Interaction |
|
|
|
|
| |
|
Betaine |
Stocking |
|
|
|
|
|
|
0 % |
2 g fish /l |
1.16±0.00a 0.98±0.01b 0.88±0.00c |
0.73±0.00a 0.65±0.01b 0.60±0.01c |
43.35±0.03a 39.70±0.14b 37.71±0.03c |
1.86±0.00a 2.02±0.01b 2.13±0.00c |
2.98±0.00a 2.87±0.01b 2.80±0.00c |
|
0.5 % |
2 g fish /l |
1.34±0.00a |
0.81±0.01a |
47.45±0.02a |
1.74±0.01a |
3.41±0.01a |
|
1% |
2 g fish /l |
1.69±0.01a |
0.94±0.01a |
54.31±0.05a |
1.05±0.00a |
3.74±0.00a |
*Means (in the same column) superscripted with different letters significantly (P≤0.05) differ
Data of protein utilization in terms of protein productive value (PPV) and protein efficiency ratio (PER) as well as survival rate (SR %) are presented as means ± standard errors in Table (5). There were no significant differences among treatments in SR. Also, there was no clear trend for the effect of betaine inclusion in Nile tilapia diet on their PPV; whereas PER significantly (P≤0.05) increased by elevating dietary betaine levels . However, increasing the stocking density of the experimented fish reduced significantly (P≤0.05) either traits (PPV % and PER). Therefore, the best PPV % was realized in the fish group received the free-betaine diet and stocked at 2 g fish/l. Yet, the best PER was reflected by the fish group received 1 % betaine supplemented diet and stocked at 2 g fish/l .
Table (5): Means* ± standard errors of protein productive value (PPV), protein efficiency ratio (PER) and survival rate (SR %) of the tested Nile tilapia fingerlings as affected by dietary inclusion of betaine at different stocking rates.
|
Treatment |
PPV |
PER |
SR | |
|
Betaine Level | ||||
|
0 % |
13.56±0.16a |
7.01±0.08c |
100±0.00 | |
|
Stocking Rate |
13.89±0.09a |
8.29±0.02a |
100±0.00 | |
|
2 g fish/l | ||||
|
Interaction |
|
|
| |
|
Betaine |
Stocking |
14.17±0.01a |
7.80±0.00a |
100±0.00 |
|
|
| |||
|
0.5 % |
2 g fish /l |
13.51±0.03a |
7.90±0.00a |
100±0.00 |
|
1% |
2 g fish /l |
13.99±0.04a |
9.02±0.00a |
100±0.00 |
*Means (in the same column) superscripted with different letters significantly (P≤0.05) differ.
In this respect, Magouz (2002b) mentioned that betaine (2-8 g / kg diet) significantly improved PER and PPV as compared with the controal (betaine free) tilapia reared in glass aquaria. Yet, Abdelhamid and Ibrahim (2003) reported lower PER and SR at 3 kg Betafin® (betaine) per ton diet for earthen ponds reared mono-sex Nile tilapia compared with the unsupplemented (control). However, Abdelhamid et al. (2004a), working on not-sexed Nile tilapia in earthen ponds also, found that 1 and 2 kg betaine / ton diet not significantly improved PER , but significantly improved PPV %. Concerning the negative effect of increasing stocking rate on PPV % and PER, Omar et al. (1997) came to similar results. They added that elevated stocking rate reduced also SR of tilapia fish. El-Saidy and Gaber (2002b) found that stocking rate did not affect SR of Nile tilapia.
Body composition:
From Table 6, it is clear that increasing dietary betaine supplementation caused increases in dry matter (DM), crude protein (CP) and to some extent also in ash contents of the tested fish. Yet, the ether extract (EE) percentage decreased by elevating the betaine level. Also, elevating stocking rate of fish positively affected their body composition concerning DM mainly and CP as well as ash, but decreased EE%. Betaine also improved fat distribution in fish fillet (Finnfeeds, 1999). In this respect, Magouz (2002b) mentioned that tilapia fish (initial weight 22g/fish) body composition was not affected by the supplementation of betaine in the diet (2-8 g/kg) containing 29 % CP for 56 days. Yet, Abdelhamid et al. (2004a) found that 2 kg betaine/ton feed of Nile tilapia (initial weight 22g/fish) reared in earthen ponds (at stocking rate of 50 thousand/faddan) led to significant (P≤0.05) increased in DM and EE and significant (P≤0.05) decreased in CP and ash percentages of the dorsal muscles. Omar et al. (1997) reported that increasing stocking density significant (P≤0.05) lowered DM and CP contents of O. nilaticus but not affected EE and ash contents of the fish. Moreover, El-Saidy and Gaber (2002a) registered significant (P≤0.05) influences of stocking density of whole fish body composition as % of DM , CP, EE and ash, since DM, EE and ash contents decreased whereas CP% increased by the increase in stocking rate . A negative relationship was noticed between CP and EE contents of fish body but a position relationship between CP and ash contents was recorded too (Abdelhamid et al ., 1999 & 2000 and El-Saidy and Gaber , 2002b).
Table (6): Means* of carcass chemical composition (%dry matter bases) of Nile tilapia fed on the experimental diets containing different level of betaine.
|
Treatment |
DM |
CP |
EE |
Ash | |
|
Betaine Level | |||||
|
0 % |
27.24±1.65b |
52.47±0.04c |
32.04±0.34a |
15.48±0.31b | |
|
Stocking Rate |
25.94±1.01c |
54.09±0.99c |
29.73±1.47a |
16.16±0.49b | |
|
2 g fish/l | |||||
|
Interaction |
|
|
|
| |
|
Betaine |
Stocking |
27.43±0.00b |
52.40±0.03b |
32.54±0.00a |
15.02±0.03b |
|
0 % |
2 g fish /l | ||||
|
0.5 % |
2 g fish /l |
23.68±0.00c |
54.48±0.00c |
28.98±0.00a |
16.53±0.00c |
|
1% |
2 g fish /l |
26.72±0.32c |
55.39±0.00c |
27.68±0.00a |
16.93±0.00a |
*Means (in the same column) superscripted with different letters significantly (P≤0.05) differ.
Economic efficiency:
The increase in feed intake by elevating betaine levels in the fish diet led to increased feed costs , but was accompanied with higher fish weight gain; so, led to lower feed costs/kg fish weight gain, i.e. caused economical feeding and production (Table 7). This result disagreed with the findings of Abdelhamid and Ibrahim (2003) who found that adding 3kg betaine/ton of mono-sex Nile tilapia diet led to lower fish productively, higher feed costs/kg weight gain, lower feed efficiency and hence lower economic efficiency than the un-supplemented (control) earthen ponds.
Yet, in another study (Abdelhamid et al., 2004b), the net return from earthen ponds stocked with un-sexed Nile tilapia and fed a diet containing 2kg betaine /ton diet was higher than the unsupplemented ponds, this was due to the higher final biomass and % tilapia of class No.1 as well as higher dressing % and boneless meat % for betaine usage. However, betaine significantly improved the growth of fish, so led to markedly better production economy. Recently, Bakeer and Mostafa (2006) mentioned that dietary inclusion of betaine improved the economic efficiency of tilapia production.
Generally, there is a negative relationship between stocking density and fish production (g/fish) with r2 = 0.996 as calculated by Huang and Chiu (1997) for tilapia fry. Also, El-Saidy and Gaber (2002b) found that 75 fish/m3 as stocking density was lower in net profile than 25 or 50 fish/m3, since high rearing density causes deleterious effect in fish farm (Abdel-Tawwab et al.,2005).
Table (7): Effect of different betaine levels and density rates on economic efficiency of Nile tilapia (means* <± SE).
Treatment |
Feed intake (g) |
Cost(LE of one ton diet) |
Total gain(g) |
Feed cost/kg gain(LE) | |
|
Betaine Level | |||||
|
0 % |
40.25±0.27c |
1758.64±0.17c |
20.19±0.27c |
0.17±0.00b | |
|
Stocking Rate |
48.37±0.53a |
1872.24±11.02a |
28.20±0.25c |
0.15±0.00c | |
|
2 g fish /l | |||||
|
Interaction |
|
|
|
| |
|
Betaine |
Stocking |
43.35±0.03a |
1757.64±2.18a |
23.27±0.01a |
0.15±0.00c |
|
|
| ||||
|
0.5 % |
2 g fish /l |
47.45±0.02a |
1872.24±2.18a |
27.21±0.17a |
0.16±0.00b |
|
1% |
2 g fish /l |
54.31±0.05a |
1986.84±2.18a |
34.12±0.07a |
0.15±0.00c |
*Means (in the same column) superscripted with different letters significantly (P≤0.05) differ.
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Authors: Abdelhamid* , A. M. ; M. A. Ibrahim** ; Nagwa A. Maghraby*** and A. A. A. Soliman***
* Animal Production Department, Faculty of Agriculture, Al-Mansourah University, Egypt.
** Animal Production Department, Faculty of Agriculture, Kafr El-Shiekh University, Egypt.
*** Animal Production Department, National Research Center, Cairo, Egypt.
United States
