Effect of diets with graded levels of inclusion of cotton and sunflower seed cakes on the growth performance and feed utilization of Nile tilapia, Oreochromis niloticus

M Aanyu, C Carpaij* and M Widmer*

National Fisheries Resources Research Institute (NaFIRRI)
Aquaculture Research and Development Center (ARDC),
P O. Box 530, Kampala, Uganda
mergieaanyu@yahoo.com
* Zurich University of Applied Sciences (Switzerland)
Institute of Natural Resource Sciences (IUNR)
Gruental, CH-8820 Waedenswil

Abstract

The effect of diets with graded levels of cotton (CC) and sunflower (SF) seed cakes on the growth and feed utilization of Nile tilapia, Oreochromis niloticus was determined. The fish were grown for a period of 90 days in 15 “happas” representing 5 treatments namely; SF25CC10 - 10% C and 25% S; SF20CC15 - 15% C and 20% S; SF15CC20 - 20% C and 15% S; SF10CC25 -25% C and 10% S and CTL was a commercial feed used as the control. Each treatment was replicated three times.  The “happas” were 1m3 with a mesh size of 1mm. They were placed in a 1,450M2 pond with an average depth of 1 meter. 

 

The control diet had a significantly higher final weight, daily weight gain (DWG), condition factor, and the most efficient food conversion ratio (FCR) and protein utilization efficiency (PER) than the test diets.  Among the test diets, SF15CC20 had the highest absolute values for final weight, DWG, FCR and PER indicating that inclusion of up to 15% of sunflower and 20% of cotton seed cakes alongside the ingredients used in this study could be used for pond production of Nile tilapia.

Key words: Fish feed, “happas”, plant-based protein, pond

Introduction

Globally, Nile tilapia (Oreochromis niloticus) is an important aquaculture species (FAO 2010) and in Uganda, it is the second most farmed fish species (FAO, 2011). This is because it can grow fast, is easy to breed, can tolerate adverse environmental conditions, has good taste, and market price (FAO 2011). However, to attain fast growth and profit, the fish have to be fed on good quality and cost-effective feed with 25% - 35% protein level (NRC 1993 and Jauncey 1998). Feed accounts for over 50% of production costs in fish farming (Coyle et al 2004). The protein component of the diet is the most expensive nutrient (Winfree and Stickney 1981 and Keembiyehetty and Silva 1993) and for several years, fishmeal has been used as the major source of protein (FAO 2010). However, the supply of fish meal has become insufficient and expensive (Tacon and Metian 2008; Otubusin et al 2009 and Li et al 2010), affecting profitability of fish farming. To reduce on the expenditure on fish feeds, there is need to develop low-cost but efficient diets using cheaper and sustainable ingredients.

 

Studies have been carried out to identify alternative protein sources that can be used as partial or full substitutes for fish meal in practical diets for fish (Balal et al 1995; Gomes et al 1995; El-Sayed 1990 and 1998; Barrow et al 2007, Nyina-wamwiza et al 2007, Soltan et al 2008).  Among the potential alternatives are non-conventional ingredients with little or no use as human food such as blood meal, brewery wastes, poultry and fish by-products, cotton- and sunflower-seed cakes (Jauncey 1998; Mbahinzireki et al 2001; Coyle et al 2004; Subhadra et al 2006 and Ogunji et al 2008).  Cotton seed cake and sunflower seed cake are obtained after the removal of oil from the seeds. They are available in many rural areas in developing countries especially in sub-saharan Africa and have been found to contain 25 % to 45 % crude protein level (Jauncey 1998 and Maina et al 2007) which can enhance the performance of Nile tilapia above levels attained with natural food alone (Jauncey 1998). However, just like other plant protein sources, the amino acid profiles of cotton seed cake and sunflower seed cake are not well balanced as that of fish meal, making them inappropriate for use as single sources of dietary protein for fish (Noreen and Salim 2008 and Soltan et al 2008). Therefore, in order to obtain the required essential amino acid profile for the cultured fish, it is appropriate to use a combination of different plant protein sources to complement one another (Soltan et al 2008). In addition, optimal levels for inclusion of the selected plant protein sources have to be used.

 

This study was therefore carried out to determine the growth performance and feed utilization efficiency of Nile tilapia fed on diets with graded levels of inclusion of cotton- and sunflower- seed cakes as the main protein sources.  

Materials and methods

Experimental site

 

The experiment was carried out for a period of 90 days at the Aquaculture Research and Development Centre (ARDC) located in Kajjansi, Wakiso district, Uganda.

 

Experimental diets

 

The ingredients used to formulate the experimental (test) diets were obtained from Kampala city (Table 1) in Uganda. Fresh blood was collected from an abattoir, boiled and sundried while soya beans and cotton seed cake were heat treated at 40-50^oC for 10 minutes to deactivate anti-nutritional factors.

 

WinPas software was used for deriving the formula for the test diets as provided in Table 1. Four test diets (SF25CC10, SF20CC15,  SF15CC20 and SF10CC25) with a 25% crude protein level were formulated with graded levels of inclusion of cotton seed cake and sunflower seed cake as the main protein sources (Table 1).

All the ingredients were ground and sieved using a 0.2mm mesh size sieve. Proximate analysis of the sieved ingredients was carried out (Table 2). The ingredients used for making each diet were mixed by hand for at least 5 minutes in order to ensure even distribution of ingredients within the mixture. Wheat flour was used as a binder. Each mixture was made into a dough using 500ml of water per kilogram of mixture. The dough was pelleted using a mincer. The pellets were dried in a solar drier at a temperature of 40-60^oC. Six (6) kilograms of each test diet were made. A commercial feed manufactured in Uganda (Ugachick Poultry Breeders Company Ltd) with a 25% crude protein level was used as a control (CTL). Each of the diets represented a treatment.

Experimental fish and feeding procedure

 

Mixed sex Nile tilapia fingerlings were obtained from the ARDC, acclimated to the experimental conditions for 2 weeks and size-graded to obtain fish with no significant differences in initial weights between treatments (Table 4). The fish in each treatment were fed on their respective diets three times a day between 9 - 10 am, 12 am - 1 pm and 4 - 5 pm at a feeding rate of 4% of the live body weight per day.

 

Experimental facilities and design

 

The experiment was conducted in a pond with a water surface area of 1,450m² (44m×33m). The water depth at the inlet side was 1 m and 1.5 m at the outlet side. The experimental fish were grown in 15 “happas” placed in the pond. Fifteen “happas” were used because there were 5 treatments (4 test diets and the control) and each treatment was replicated 3 times. Each “happa” measured 1x1x1m (length, width and height) and had a mesh size of 1mm. The “happas” were supported using wooden poles and 70cm depth of the “happas” was submerged in the pond water. The “happas” were installed in 3 rows and each row had 5 “happas” with each treatment represented in each row. The “happas” within the same row were installed 3 m away from each other while the “happas” at the end of each row were installed 8 m away from the pond dyke. The distance between the rows was 10 m. At the inlet side, the first row of “happas” was installed 10 m away from the rear pond dyke while at the outlet side; the last row of “happas” was installed 11 m away from the hind pond dyke. A 2 inch net was placed on top of each “happa” to prevent birds from preying on the fish. Each “happa” was stocked with 35 mixed sex Nile tilapia. In order to minimise clogging of the “happas” with organic matter, they were cleaned after every three days using a brush.

 

After every three weeks, all the fish in each “happa” were removed using a scoop net and their individual weights (g) and total lengths (cm) were measured in order to assess growth performance. A day prior to fish measurement, the fish were starved. An electronic scale, model 88 FURI, measuring maximum 200g (precision 0.1g) was used for weighing the fish. A measuring board with a meter ruler attached was used for determining the total length of the fish.

 

Water quality parameters (dissolved oxygen, temperature, pH and ammonia) within the pond were also monitored throughout the study in order to maintain the water quality within the optimum range for Nile tilapia growth (Boyd and Craig 1998).  Water temperature and dissolved oxygen were measured daily at 8:00am and 12noon at the front, middle and back of the pond. The pH, ammonia and conductivity were measured twice a week at 8:00am also at the front, middle and back of the pond. The data recorded indicated that the water temperature ranged from 24.1 ± 0.9^oC at 8:00am to 26.7 ± 1.6^oC at 12:00 noon and the dissolved oxygen concentrations were 4.1 ± 1.6 mg^-l at 8:00am and 7.2 ± 1.6 mg^-l at 12:00 noon. The pH of the water was 7.9 ± 0.4, ammonia levels were less than 0.2 mg^-l and the conductivity was 353 ± 216. 

 

At the end of the experiment, the total number of fish in each “happa” was recorded in order to determine the percentage fish survival.

 

Chemical analysis of feeds

 

The proximate composition (crude protein, crude lipid, crude fibre, ash, moisture, Nitrogen free extract) of the experimental diets was analyzed following the procedures described by the AOAC (1990). Crude protein was estimated by measuring the nitrogen content of the ingredient using the micro-Kjeldahl method and calculating the crude protein level by multiplying the nitrogen content by 6.25. Crude lipid was determined by ether extraction method using soxhlet apparatus. Ash content was measured by placing a sample of known weight in a furnace of 470-550^oC for 3 hours and the remaining weight was considered the ash. Moisture content was measured by placing a sample of known weight in an oven set at 105-110^oC until the sample attained a constant weight. The lost weight from the sample was considered the moisture content and the remaining weight dry matter.

 

Data analysis

 

Growth performance

 

Growth performance was analyzed in terms of daily weight gain (DWG) of the fish, percentage (%) fish survival, and condition factor (CF) using the formulae below: 

 

DWG (g/day) = (W_f - W_o)/T

 

W_f  is the weight (g) of fish at the end of the experiment

W_o is the weight (g) of fish at the beginning of the experiment

T is the number of experimental days

 

% survival = N_f × 100%

                      N_o

 

N_f  is the number of surviving fish in each treatment by the end of the experiment

N_o is the number of fish in each treatment at the start of the experiment

 

CF = W × 100

              L³

 

W (g) is the weight of the fish

L (cm) is the total length of the fish

 

Feed utilization efficiency

 

Feed utilization efficiency was assessed by determining food conversion ratio (FCR), and protein utilization efficiency (PER) using the formulae below:

 

FCR = F

        (W_f -W_o)

 

F is the weight (g) of food supplied to fish during the experimental period

W_f  is the weight (g) of fish at the end of the experiment

W_o is the weight (g) of fish at the beginning of the experiment

 

PER = W_f -W_o

              F×p

W_f  is the weight (g) of fish at the end of the experiment

W_o is the weight (g) of fish at the beginning of the experiment

F is the weight of feed (g) supplied over the experimental period

p is the fraction of crude protein in the feed

 

Statistical analysis

 

Differences in growth performance and feed utilization efficiency between treatments were determined using SPSS software. One-way analysis of variance was carried out and significant differences were considered at P<0.05 using Duncan`s multiple comparison test.  

Results

 Proximate analysis of the experimental diets

 

Table 3 shows the analyzed proximate composition of the experimental diets.

Growth performance

 

Fish fed on the control diet had a higher final weight than those fed on SF25CC10, SF20CC15,  SF15CC20 and SF10CC25 (Table 4).  No differences were recorded in final weight between the fish fed on feeds SF25CC10, SF15CC20 and SF10CC25 while fish fed on  SF20CC15 had a lower final weight than on the other diets.  Daily weight gain and condition factor were also higher for the fish fed on the control diet.  Survival rates did not differ between the treatments.

Feed utilization efficiency

 

Fish fed on CTL had a better feed conversion ratio (FCR) and protein efficiency ratio (PER) compared to the other treatments (Table 4).  

 

Discussion

Given that fish live in water, water quality parameters greatly influence their physiological processes (Boyd and Tucker 1998). During this experiment, water quality parameters were measured (dissolved oxygen, pH, temperature, conductivity, ammonia) within the experimental pond and were found to be within the recommended range for Nile tilapia growth and development (Boyd and Tucker 1998; Stickney 1979). This implies that the experimental diets had no negative effect on the pond water where the experimental fish were grown.

 

Overall, the results of this study indicate that the control diet (CTL) had the best growth performance (weight gain) and feed conversion (FCR and PER). 

 

The significantly higher final weight, daily weight gain and condition factor attained with the control diet is attributed to the fact that the control diet contained some fish meal as a protein source. Fish meal is a more readily digested and assimilated ingredient than cotton seed cake, sunflower seed cake and maize bran that have higher fiber content (Tacon et al 2009). The fiber in plant ingredients is known to reduce feed intake, decrease the time the feed spends in the gut and consequently diet digestibility and nutrient bio-availability (Espe et al 1998; Cheng and Hardy 2002 and Nyina-wamwiza et al 2007).  In addition, cotton seed cake and sunflower seed cake contain anti-nutritional factors (Nyina-wamwiza et al 2007) that might have persisted in the ingredients even after heat treatment and cooking of the dough before making the pellets. Cotton seed meal may have 0.4 to 1.7% of gossypol that can be toxic to fish when present in large amounts in the diet (Soltan et al 2008). The daily weight gains obtained in this study (Table 4) were considerably lower than the value of 1.32 g/day obtained by Nguyen and Preston (2011) in an experiment where Nile tilapia  were grown in open ponds (3 fish/m²) fertilized with biodigester effluent and supplemented with duckweed. SF15CC20 could be optimized for semi-intensive pond production of Nile tilapia by combining it with pond fertilization as demonstrated in other studies carried out by Waidbacher et al (2006) and Diana et al (1994). They demonstrated that synergy between supplementary feed and natural food obtained from pond fertilization was a more appropriate feeding strategy for pond production of Nile tilapia than the provision of artificial feed alone.  It could further reduce artificial feed input and production costs given that the main protein sources (sunflower and cotton seed cake) used in this study are cheaper compared to the conventional foodstuffs like fish meal. Thus, this feeding strategy has potential to optimize the performance of SF15CC20 and benefit many small holder farmers especially those in developing countries.

 

There are however contradicting reports on the performance of fish on plant-based diets. Some authors state that over 45% replacement of fish meal with plant ingredients significantly reduces the growth performance   of fish (Fournier et al 2004 and Soltan et al 2008) while others observed that partial or complete replacement of fish meal with plant ingredients did not inhibit growth performance (Lee et al 2002;  El-Saidy and Gaber 2003). The disparity in these findings could be attributed to the fact that the quality of ingredients used to formulate feeds often varies; consequently, the fish do utilize the nutrients differently (Soltan et al 2008).

 

Just like the growth performance, the best feed conversion ratio and protein efficiency ratio were realized with the control diet. The protein efficiency ratio mainly depends on the quantity and quality of the protein in the diet (Cacho et al 1990). When the amount of the bio-available protein in the diet is below the requirement of the cultured fish, fish often do not grow fast to attain their maximum growth potential (Kolsater 1995 and Turano et al 2002). In this study, the best FCR and  PER obtained with the control diet is attributed to efficient utilization of the nutrients in the diet particularly fish meal which has a well balanced amino acid profile and no anti-nutritional factors.  

Conclusion

• Up to 15% inclusion of sunflower seed cake and 20% of cotton seed cake alongside the ingredients used in this study could be used for pond production of Nile tilapia.
  
  
• The formulation could be used by small holder rural farmers to boost aquaculture production especially when combined with pond fertilization.  However, further studies need to be carried out to optimise the efficiency (FCR) at which Nile tilapia utilize the diet.

Acknowledgement

 We thank the Swiss Agency for Development and Cooperation - SDC for funding this KFH-DC study at the Aquaculture Research and Development Center (ARDC), Kajjansi, Uganda. We also appreciate the technical advice given by the Head of the aquaculture research center.  We acknowledge the assistance from the Uganda-Chinese Agricultural Technology Demonstration Project for allowing us to use the pond. We also thank ARDC technicians (Ondhoro Constantine Chobet, Wannume Kenneth and Kityo Godfrey), interns (Syndey and Enid) and pond attendants (Joseph and Kalema) for participating in feed formulation, data collection and feeding the fish.

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