Growth of red tilapia (Oreochomis mossambicus) and black tilapia (Oreochomis niloticus) with common carp (Ciprinus carpio) in monoculture and polyculture by using natural feed in organic fertilizer pond from biodigester effluent 

Nguyen Huu Yen Nhi and T R Preston*

An Giang University, 25 Vo Thi Sau St., Long Xuyen City, Vietnam
nhynhi@agu.edu.vn
* TOSOLY, AA 48 Socorro, Colombia.

Abstract

This experiment was carried out in the research farm of An Giang University from November 2011 to February  2012 to compare growth of red tilapia (Oreochomis mossambicus) and black tilapia (Oreochomis niloticus) in monoculture and polyculture with common carp (Ciprinus carpio) in an outdoor natural pond system, using biodigester effluent as fertilizer and duckweed as feed supplement. There were four treatments with three replicates in a completely randomized design with only Tilapia or Tilapia and Common carp (5:1) at 5 fish/m² in the natural ponds (4m²), seeded with duckweed and fertilized with biodigester effluent.

 Growth rates of black tilapia were significant higher than red tilapia especially, daily weight gain were 1.62 and 1.30, respectively. However, there were not significant different in growth rates of black tilapia treatment was cultured with common carp compare with red tilapia treatments. In addition, growth rates of common carp were no differences between raising with black or red tilapia. Besides, the survival rate of fish in four treatments was not affect by experimental factor. Furthermore, water quality parameters were no significant differences between treatments. However, the number of phytoplankton and zooplankton increase during the experiment time.

Key words: Duckweed, feed supplement, recycling

Introduction 

Fish production makes an important contribution to global food supply. We also have to cope with the considerable and increasing demand of finding the new feed sources for fish by using natural feed, especially in response to climate changes and depletion of non-renewable resources.

Moreover, the human population is increasing in developing countries so the animal production demands also go up. When animal productions increase lead to increase the biological water pollution by their waste water and excreta. That is the problem in the rural areas of Mekong Delta for that reason waste water from the animal farm needs to have the method to treat (Tran Thi Phan and Takeshi Watanabe 2002). Actually, there are many methods to resolve this problem such as applying biodigester system. Their product are gas production for cooking and biodigester effluent can be apply to crops like water spinach (Ly Thi Luyen, 2003; Ho Bunyeth 2003) and fish pond for fish (Sen Sorphea et al 2010) or water plant like duckweed (Le Ha Chau 1998).

Duckweed (Lemna spp.) is rich in nutrients. It has been used as a main protein supplement for pigs (Bui Hong Van et al 1997), ducks (Bui Xuan Men et al 1995; Nguyen Duc Anh et al 1997b) and fish (Latsamy and Preston 2007) and also as a source of minerals for ruminants (Leng et al 1995). Duckweed has high nutritive value, especially the high protein content and also because of its capacity to grow rapidly on nutrient-rich waste water and produce biomass rich in protein (Leng et al 1995) so that has been used as the natural source for fish in the natural fish culture system (Sen Sorphea et al 2010).

The biodigester effluent has high nutrient content up to   1004 mg N/litre of which 40% is ammonia-N (Bui Phan Thu Hang 2003).

The aquaculture systems is mostly practiced in cage or pond  culture. The fish production can be monoculture and poly-culture. However, to optimize the use of natural resources, the integration of animals, crops and fish is an ideal strategy. In recent years, giving attention on the role of biodigesters as a key component of the farming systems. The recycling of waste gives additional value to animal wastes through gas production, produce good quality of organic materials and the control of pathogens. The effluent from the biodigester has been used to produce plankton for fish.HHHH

It is considered that the apply of effluent from biodigester for fish pond to growing duckweeds and phytoplankton could be a way of increasing feed availability for fish and at the same time reducing problems of pollution to the environment.

Hypothesis

The environmental impact can be reduced by reuse the nutrient in biodigester effluent as nutrient for duckweed in fish pond. Organic fertilizer from biodigester effluent can use for tilapia, common carp and integrated tilapia and common carp in natural system.

Objective

Assessment reusing waste water from biodigester effluent on growth of fish in monoculture and polyculture.
Compare growth rate of length and weight, yield of black tilapia and red tilapia in monoculture and polyculture with common carp by using natural feed in organic fertilizer pond from biodigester effluent. 

Materials and methods 

Location and climate 

This experiment was conducted in the experimental farm of An Giang University, Long Xuyen City, Vietnam. The climate is tropical monsoon, with a rainy season between May and October and a dry season from November to April. The mean air temperature is 27°C and annual rainfall 1400-1500 mm. The duration of the study was 90 days, from December to March 2011. 

Experimental treatments and design  

The experiment was conducted in a completed randomized design (CRD) with 4 treatments and 3 replicate. Individual treatments were: 

• BT: Black tilapia only 

• BTC: Black tilapia: common carp (5:1) 

•  RT: Red tilapia only 

• RTC: Red tilapia : Common carp (5:1)

Fingerlings  

Black tilapia, red tilapia and common carp around 7.43 – 7.5g/fish were bought from the hatchery in Long Xuyen City. 

Management and measurement  

Twelve earthen ponds (around 2m depth x 2 m wide x 2m length) (photo 1) were lined with plastic sheet to avoid filtration of water. Tilapia and common carp were put in the pond suitable for each treatment. Biodigester effluent was taken from biogas system and was supplied for fish pond 2.98g N/day in during the experiment time. It was supplied nutrient for growing of phytoplankton in the ponds, especially duckweed as the natural feed source for fish. It was made sure that duckweed always account for 70% of ponds to have shade and good condition for fish. The amount of effluent put into the ponds and duckweed in the pond will be recorded and take effluent samples for analysis each two weeks. The amount of phytoplankton in the ponds were been also counted periodic every two week to estimate natural feed source supplement for fish besides duckweed.  

 Water quality was observed and managed every day during the experiment time. One-third of the water in the ponds was exchanged for each time water exchange. Not clear Nhi~~The temperature, oxygen dissolved (DO), nitrite (NO₂^-), total ammonia nitrogen (TAN), pH and transparency of treatments was measured every two weeks  during the experiment time.  

The weight and length of fish were measured each month periodic such as at the beginning of the experiment, one month after stocking, two month after stocking and at the end of the experiment to compare growth rate of length and weight, yield of tilapia and common carp in monoculture and polyculture by using natural feed in organic fertilizer pond from biodigester effluent. 

Specific growth rate (SGR) was calculated as SGR (%/day) = 100 [Ln(w_f) – Ln(w_i)]/T ….(i) 

where:                

   W_f: Final weight (g) 

    W_i: Initial weight (g) 

     T: Number of experimental days 

Daily weight gain (DWG) was calculated as: 

DWG (g/day) = (w_f - w_i)/T ……………….(ii)

Survival rate (SR%) was calculated as: 

SR (%) = 100[number of fish harvested/initial number of fish] …….(iii) 

Chemical analysis 

Feed samples were analyzed for DM, nitrogen (N), ether extract, and organic matter (OM) according to the procedures of AOAC (1990).
 

Statistical analysis 

The data for amount of biodigester effluent, growth rate, survival rate and amount of plantonk were analyzed using the General Linear Model (GLM) of the ANOVA program with the Tukey pair-wise comparison in Minitab software (Minitab release 13.3, 2000). Sources of variation were: Fish species, culture system, interaction culture system* fish species and error. 

Results and discussion

Water quality 

Most of quality parameters were similar for all treatments (table 1). In addition, water temperature, pH, and dissolved oxygen higher in the afternoon than in the morning. However, the water quality in all treatments was within the acceptable range for the normal growth of fish (Boyd 1990).

Phytoplankton (phytoplankton) called algae (algae) live suspended in water, there is no active swimming ability. Chlorophyta was the main group of algae especially chlorella had the highest proportion when collecting samples for analysis in species composition of phytoplankton in the pond experiments. 

Phytoplankton density was fluctuated in each treatment and increasing with culture periods (Figure 1) because favorable weather conditions, high and stable temperature with nutrient accumulation in ponds created highly favorable conditions for algae to thrive in this experiment. However, the water changes periodically in the experiment, so the density of phytoplankton in the pond was always increased, but not so high and not affected the survival of fish and the growth of the fish.

The variations of zooplankton also differ among treatments during rearing and increase over time (figure 2). Algae density from 193-289 ind./ml after 15 days of the experiment and gradually increases to 1186 - 1335 ind./ml at the end of the experiment. This demonstrated that nutrient in the pond was always well maintained. Thus, the addition of biodigester effluent was make the development of zooplankton stronger, but does not affect the growth and development of fish in the experiment.

Chemical composition of duckweed  

Table 2 showed that the protein level in the duckweed was 25,49% lower than than the  levels of 31%  reported by San Thy et al. (2004) and 30.5% observed by Sen Sorphea et al (2010), but higher than levels of 19% reported of Yen Nhi and Preston (2011).  

The effluent contained 876 mg N/liter which was higher than in previous studies of San Thy et al (2004) (835 mg/liter) and Pitch Sophin and Preston (2001) (range from 290 to 470 mg/liter), but lower than in previous research of Yen Nhi and Preston (2011) (900 mg/liter). This probably reflected differences in the feed received by the pigs and the concentration of solids in the influent to the biodigester.

Duckweed was supplied to fish pond on 15th day after beginning the experiment. Total weight of duckweed supplied for each pond was from 33.8 kg to 34.9 kg. There was insignificant differences among treatments (p>0.05) (Table 3).

 Growth performance  

 Table 4 showed the survival rate of tilapia was insignificant difference among treatments (p=0.508), the rate ranged from 93-100%. In the two treatments, black tilapia combined with common carp and red tilapia combined with common carp had the highest survival rate was 100%, followed red tilapia treatment 98% and finally was black tilapia treatment 93%. Moreover, the survival rate of carp was also 100%, which showed that the survival rate of tilapia raised in ponds using natural food was very high and combination of tilapia and other fish (common carp) were also good. The evidence was two treatments had the highest survival rates were treatments tilapia polyculture with common carp. This may prove food did not affect the survival of fish in the experiment. 

 Table 5 showed the difference in the growth target of black tilapia and red tilapia. Weight gain of black tilapia was 144 g higher than red tilapia was 116 g. Similarly, specific growth rate, daily weight gain and daily length gain of black tilapia were higher than red tilapia (p<0.01). Although the two species were kept in the same conditions and using the same foods and polyculture with common carp but there was ifference in the growth target, black tilapia was higher red tilapia in all growth targets. Thus we can say, the growth rate of black tilapia higher than red tilapia when cultured in same conditions. 

 The weight gain of black tilapia treatment higher than and significant differences with other treatments (p<0.01) when feeding in the same environmental conditions and using the same kind of food was duckweed, but the treatment of black tilapia combined with common carp was no significant difference with two treatments had red tilapia (table 6 and figure 3). However, weight gain of common carp in 2 treatments combined with black tilapia or red tilapia were no difference (p=0.614). Therefore, there were no affected on weight gain when polyculture two kind of fish together.
 

 Changes in weight: length ratio

 Both species of tilapia showed an increase in the weight: length ratio as the experiment progressed (Table 7); however, the differences between treatments were insignificant (p>0.05), except at 30 days. 

 Economic analysis 

 Table 7 showed that the yield of the black tilapia combined with common carp treatment was highest (7245 kg/ha) followed by black tilapia treatment and lowest was red tilapia combined with common carp treatment. However, output and productivity of fish in all treatments did not differ statistically (P> 0.05).

Productivity between polyculture treatments and monoculture treatments also not much difference, but black tilapia treatments were higher than red tilapia treatments in the experiment. Thus, when applied to realistic models we can choose polyculture farming and select the species. According to the results of this experiment, the polyculture of black tilapia and common carp with naturally foods had high yield when reared in ponds with the same conditions compared to other models in the experiments.

Conclusions   

• Environmental factors including temperature, pH, DO, TAN, NO2 were in the range suitable for the growth and development of fish in the experiment.

• The growth in weight and length of the black tilapia treatments were higher than red tilapia. Daily weight gain and daily length gain of black tilapia treatment   was highest and red tilapia combined with common carp treatment was lowest.

• The highest yield was treatment polyculture black tilapia and common carp. In contrast, red tilapia with common carp polyculture treatment was lowest in productivity.

References

Boyd C E 1990 Water quality in ponds for aquaculture. Alabama agriculture experiment station, Auburn University. Birmingham Publishing Co. Birmingham, Alabama. First printing 5M, December 1990.

Bui Phan Thu Hang 2003 Effect of dimensions of plastic biodigester (width:length ratio) on gas production and composition of effluent. http://mekarn.org/msc2003-05/miniprojects/webpage/hangctu.htm 

Ho Bunyeth  2003: Biodigester effluent as fertilizer for water spinach established from seed or from cuttings;  Retrieved , from MEKARN Mini-projects. http://www.mekarn.org/MSc 2003-05/miniprojects/web page/buny.htm

Le Ha Chau 1998 Biodigester effluent versus manure, from pigs or cattle, as fertilizer for duckweed (Lemna spp.). Livestock Research for Rural Development (10) 3:f http://lrrd.org/lrrd10/3/chau2.htm

Ly Thi Luyen 2003: Effect of the urea level on biomass production of water spinach (Ipomoea aquatica) grown in soil and in water;  Retrieved , from MEKARN Mini-projects. http://www.mekarn.org/MSc 2003-05/miniprojects/web page/luyen.htm

Pich Sophin and Preston T R 2001 Effect of processing pig manure in a biodigester as fertilizer input for ponds growing fish in polyculture, Livestock Research for Rural Development.  http://www.lrrd.org/lrrd13/6/pich136.htm

San Thy, Khieu Borin, Try Vanvuth, Pheng Buntha and T R Preston 2004 Effect of water spinach and duckweed on fish growth performance in poly-culture ponds. Livestock Research for Rural Development. http://www.lrrd.org/lrrd20/1/sant20016.htm

Sen Sorphea, Lundh T, Preston T R and Khieu Borin 2010 Effect of stocking densities and feed supplements on the growth performance of tilapia (Oreochromis spp.) raised in ponds and in the paddy field   MSc Thesis, MEKARN-SLU http://www.mekarn.org/MSC2008-10/theses/sorp_1.htm

Tran Thi Phan and Takeshi Watanabe 2002 Development of the new technologies and their practice for sustainable farming systems in the Mekong Delta. Proceeding of the 2002 Annual Workshop of JICAS Mekong Delta Project. November 26-28, 2002. College of Agriculture, CanthoUniversity. Vietnam
 

Yen Nhi N H and Preston T R 2011 The growth and economics of integrated culture of Tilapia (Oreochomis niloticus) and Common carp (Ciprinus carpio) in an indoor intensive system with earthworms as feed and in natural ponds fertilized with biodigester effluent and supplemented with duckweed. Livestock Research for Rural Development. Volume 23, Article #161. Retrieved May 27, 2012, from http://www.lrrd.org/lrrd23/7/nhi23161.ht

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