Effects of dietary protein levels on performance of African catfish Clarias gariepinus in fertilized and unfertilized earthen ponds

J M Mwangi, J G Maina and C K Gachuiri

University of Nairobi, Department of Animal Production, P O Box 29053-00625, Nairobi, Kenya.
jackson.muchiri85@gmail.com

Abstract

The recommended protein levels in catfish diets aim to maximize growth with little regard to production costs. A study was done in Kirinyaga County, Kenya to evaluate the effects of dietary protein levels on performance of C. gariepinus in fertilized and unfertilized earthen ponds. Two earthen ponds, one fertilized with chicken manure and the other unfertilized, were stocked with C gariepinus fingerlings weighing 3.29±0.329 g, in 2m ² happas at 10 fish/m². Four iso-caloric diets (3000 kcal/kg) with varying levels of rice milling byproducts and containing protein levels of 25%, 30%, 35% and a control diet (no rice byproducts and 35%CP) were formulated. The control diet and 25%, 30% and 35% protein level diets cost, 47.8, 34.5, 38.3 and 42.6 KSh/kg of diet respectively. All diets were fed to the fish in triplicate happas for 128 days. The parameters that were monitored were growth, survival, feed utilization and water quality. The average dissolved oxygen content and weight gains of fish in the fertilized pond was higher than the unfertilized pond. The fish fed the diet containing 25% CP had the highest protein efficiency ratio (2.18) in the fertilized pond. The study concluded that the fish fed the low cost 25% CP diet in the fertilized pond had performance parameters close to those fed the other diets and is therefore suitable for C. gariepinus culture in fertilized earthen ponds when considering the production cost.

Key words: cost, growth, production, rice byproducts, water quality

Introduction

Protein content of diets is usually the major consideration during feed formulation due to its nutritional importance and relatively high cost followed by the energy level (Craig and Helfrich 2002; Munguti et al 2012). A standard dietary crude protein level recommendation for African Catfish Clarias gariepinus has not been established. The National Research Council (1993) has established a standard dietary protein requirement for Channel catfish Ictalurus punctatus ranging between 32-36%. These levels have been determined using young fish under optimum environmental and other conditions and are formulated with the objective of maximizing growth with inadequate consideration given to production costs or profit maximization (Parker 2002). The protein levels have also been determined under intensive production systems. As such, there is need to evaluate the performance of C. gariepinus under varying dietary protein content to assess growth and the economics of production in lower level production systems where the ponds are fertilized and water is static.

Clarias gariepinus is an omnivorous fish which has relatively better utilization of high protein than high carbohydrate diets (FAO 2015). This is a challenge to its sustainable culture as the protein fraction of the diet is more expensive compared to carbohydrates (Munguti et al 2012). In this study, rice milling byproducts, which are abundant in the study site in Kirinyaga County (Government of Kenya 2009), were incorporated as cheap sources of energy.

A major challenge encountered in the culture of fish in ponds is the poor water quality (de Graaf and Janssen 1996) resulting from decomposing left over feeds and fecal material which release ammonia from protein decomposition (Parker 2002). Pond fertilization has been used to increase the natural food for the fish and improve pond water quality; it results in growth of algae which increase dissolved oxygen concentration in the pond water during photosynthesis and also assimilate ammonia (Knud-Hansen 1998). Several studies have shown beneficial effects of fertilization in tilapia ponds (Liti et al 2002; Muendo et al 2006, Sorphea 2010; Zahid et al 2013). Studies on effects of pond fertilization for Clarias gariepinus raised in ponds are inadequate (Bok and Jongbloed 1984; Mosha 2015).

The overall objective of this study was to investigate the effects of dietary protein levels on performance of C. gariepinus cultured in fertilized and unfertilized earthen ponds and fed diets based on rice milling byproducts.

Materials and methods

Study site

This study was carried out from 15^th February, 2014 to 3 ^rd July, 2014 at the National Aquaculture Research Development and Training Center, located in Kirinyaga County, Kenya. It is 104 km NE of Nairobi at 0° 39’ S and 37° 12’ E and at an altitude of 1230 meters above sea level.

Experimental diets and design

Rice bran was purchased from a large scale rice miller in Kirinyaga County while other feed ingredients were purchased from suppliers in Nairobi. The raw materials were analyzed for nutrient content at the University of Nairobi, Department of Animal production, before inclusion in fish diets. The analysis of the feed ingredients for DM, CP, EE, CF and ash was done according to the procedures outlined by the Association of Official Analytical Chemists (AOAC 1998) prior to the diet formulations. Four iso-caloric diets (3000 kcal/kg) having protein levels of 35% (Diet 1: control), 25% (Diet 2: Low Protein), 30% (Diet 3: Medium protein), and 35% (Diet 4: High protein) were formulated and used in this study. All diets except Diet 1 (control) contained rice milling byproducts. Other ingredients included maize, wheat pollard, soybean meal and freshwater shrimp (Caridina nilotica) meal as shown in Table 1. The fish were stocked at 10 fish/m² in happas measuring 2 X 1 m each, placed in two earthen ponds, one fertilized and the other unfertilized, each measuring 150 m². Each of the four diets was fed to three groups of fish in each pond for a period of 128 days.

Management of fish

Mixed-sex Clarias gariepinus fingerlings (average weight 1.4± 0.06 g) were bought from Jambo fish farm in Kiambu County in Kenya and transported to the study site. They were acclimatized to pond conditions for a week and during this time, they were fed on the control diet (Diet 1). At the end of the week, the fish (average weight 3.29± 0.329g ) were weighed in groups of 20 fish picked at random and randomly allocated to 12 happas in each of the two ponds which constituted two blocks. The ponds were limed with agricultural lime at the rate of 2,500 kg/ha (Boyd and Massaut 1999; Ngugi et al 2007) two weeks prior to stocking. The fish were fed on the respective diets thrice a day as recommended by Aderolu et al (2010) to reduce cannibalism. This was done at 10% of their body weight when the fish (weighing 1.4± 0.06 g) were bought and was reduced to 3% of their body weight when the fish attained a weight of approximately 36 g. This was according to guidelines by Hogendoorn et al (1983), Hecht et al (1988) and de Graaf and Janssen (1996). The amount of feed was adjusted every two weeks after weighing the fish and was increased as the fish body weight increased.

One pond was fertilized with chicken manure two weeks before stocking at 25 kg dry weight per 100 m² of pond and thereafter 3 kg dry weight per 100 m² of pond every 10 days (Tacon 1988) while the other pond was left unfertilized. Water quality parameters monitored weekly were: temperature, pH, Dissolved Oxygen (DO), ammonia, nitrates, nitrites, Total Dissolved Solids (TDS), salinity and Electrical Conductivity (EC). The temperature was measured using a thermometer, DO using an oxygen probe, while pH was measured using a pH meter. Ammonia, nitrates, and nitrites were measured using kits manufactured by Colombo Aquatest kits. The TDS, salinity and EC were measured using a multi-parameter probe (HI 98282.2) manufactured by Hanna Instruments.

Data collection and analysis

The weight and length of all the fish were measured in two week intervals in order to adjust the feeding rates and to calculate the weight gain (g), Specific Growth Rate (%/day), feed intake (g), Apparent Feed Conversion Ratio, Fulton’s condition factor (Blackwell et al 2000), Protein Efficiency Ratio and Protein Intake (g). Data on performance were analyzed using two-way Analysis of Variance (ANOVA) in Genstat 13th edition. Differences between treatment means were considered significant at p<0.05 and if found to be significant they were separated using Tukey’s multiple comparison procedure. T-tests were done to compare the water quality parameters of fertilized and unfertilized ponds.

Results and discussion

Ingredient proximate components

The proximate components in the dietary ingredients are shown in Table 2. Rice milling byproducts (bran and chicken rice) were abundant in the study site and were included in the diets. Rice bran (fine) had a CP of 14.4% and CF of 10% which were higher than the CP of 11.9% and 10.8% and CF of 9.1% and 8.32% reported by Njuguna (2007) and Maina et al (2013) respectively in Kenya. However, the CP content was within the range of 13.8-15.4% reported in Uruguay (Gallinger et al 2004) but the CF was higher than that reported (7.4-8.3%) in that study. This is acceptable according to the definition of rice bran by Tacon et al (2009) who stated that it should contain a CF level of less than 13%. Chicken/broken rice, which consists of particles of rice grains that break during the milling process, had a CP of 7.87% which is close to 7.1% reported by Chau Thi Da (2012) in Vietnam.

Effects of dietary protein levels and pond fertilization on performance of Clarias gariepinus

The effects of protein levels and pond fertilization on various performance indices of Clarias gariepinus were analyzed. For all the parameters, there were no interactions between dietary protein levels and pond fertilization. The weight gain per day of the fish is shown in Figure 1.

Effects of dietary protein levels on performance of Clarias gariepinus

The effects of dietary protein levels on performance of C gariepinus are shown in Table 3. The final weight, weight gain, and Specific Growth Rate (SGR) of the fish increased with increasing protein levels. Several authors, Machiels and Henken (1985), Degani et al (1989), Ali and Jauncey (2005) and Ahmad (2008) also reported that growth of C gariepinus increased with increasing dietary protein levels. The Apparent Feed Conversion Ratio (AFCR) also improved with increasing dietary protein level. This was attributed to the fact that C. gariepinus utilizes high protein diets better than high carbohydrate diets (FAO 2015).

The Protein Efficiency Ratio (PER) of the fish decreased with increasing dietary protein levels. This is because the efficiency of utilization of protein decreases with increase in Protein Intake (Ahmad 2008; Schuchardt et al 2008).

Fish fed the low protein diet (25% CP, with rice milling byproducts) had the lowest final weight, weight gain and SGR but these parameters were not different from those of fish fed control (35% CP, without rice milling byproducts).

Figure 1. Average weight gain per day of Clarias gariepinus fingerlings fed varying protein level diets in fertilized and unfertilized earthen ponds

Effects of pond fertilization on performance of Clarias gariepinus

The effects of pond fertilization on C. gariepinus performance are shown in Table 4. Fish reared in the fertilized pond had higher final weights, weight gains and specific growth rates (259g , 1.99 g/d and 4.32%/day respectively) compared to those in the unfertilized pond (209g, 1.62 g/d and 4.15%/day respectively). Feed intake was also higher for fish in the fertilized pond (451g/fish) compared to those in the unfertilized pond (361g/fish). The performance parameters observed are comparable to those by Bok and Jongbloed (1984) and Mosha (2015) on C. gariepinus and studies on other fish species by Suresh Babu et al (2013) and Zahid et al (2013).

Effects of pond fertilization on water quality of Clarias gariepinus ponds

Ammonia, nitrate and nitrite were not detected in the pond water throughout the experimental period. Pond fertilization had no effect on pond water temperature (Table 5). This was in agreement with Suresh Babu et al (2013), Zahid et al (2013) and Mosha (2015). The recommended temperature for catfish culture ranges between 20-30°C (Parker 2002; Isyagi et al 2009; Water Research Commission 2010). Water temperature is important because fish are ectotherms (Castell 2000), and all their metabolic activities are influenced by the water temperatures.

The average dissolved oxygen, pH, conductivity, salinity and total dissolved solids of the fertilized pond (2.8 mg/l, 8.08, 226 µS/cm, 0.11 mg/l and 113 ppm respectively) were higher than for the unfertilized pond (2.15 mg/l, 7.85, 124 µS/cm, 0.06 mg/l and 61.8 ppm respectively). These are in agreement with studies done by Charo-Karisa et al (2013), Suresh Babu et al (2013), Zahid et al (2013), Palm et al (2014) and Mosha (2015). The values are within the range of water quality recommendations made for fish production (Britz and Hecht 1989; Wurts and Durborow 1992; Department of Water Affairs and Forestry 1996; Parker 2002; Stone and Thomforde 2006; Weber-Scannell and Duffy 2007; Borode et al 2008; Water Research Commission 2010; Floyd 2014).

Pond fertilization increases algae growth which carry out photosynthesis during the day thus consuming carbon dioxide (in the form of carbonic acid) and releasing oxygen into the pond water (Knud-Hansen, 1998); this increases the pH and dissolved oxygen of the pond water respectively. Pond fertilization using manure also increases the total dissolved solids, salinity and electrical conductivity of the pond water due to mineralization of the manure (release of organic and inorganic compounds into the pond water).

Conclusions

• The fish fed the low cost 25% CP diet in the fertilized pond had performance parameters close to those fed the other diets.
  
  
• Pond fertilization improved the gain in weight and specific growth rate of C gariepinus
  
  
• Inclusion of rice bran reduced the cost of C gariepinus feed
  
  
• Pond fertilization resulted in improved water quality (with regard to pH, dissolved oxygen, total dissolved solids, salinity and electrical conductivity) resulting in better performance of C gariepinus.

Acknowledgements

I would like to thank the Partnerships for Enhanced Engagement in Research (PEER) Science program, funded by the National Academy of Sciences through USAID, for funding this project. I also acknowledge the National Aquaculture Research, Training and Development Centre at Sagana for providing research facilities and the University of Nairobi for providing facilities for the analytical work.

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Received 17 January 2018; Accepted 14 February 2018; Published 1 March 2018

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