Key findings:

The study investigated the growth and nutrient utilization of Clarias gariepinus fingerlings fed diets with varying levels of cassava peels. Results showed that 10% inclusion of cassava peels led to the highest weight gain, specific growth rate, and protein efficiency ratio. This suggests that cassava peels can be a cost-effective alternative in the diet of Clarias gariepinus.

What is known and what is new?

This study investigated the growth and nutrient utilization of Clarias gariepinus fingerlings fed diets containing varying levels of cassava peels, ranging from 0% to 10%. Results showed that while the mean initial weight did not differ significantly among diets, there were significant differences in mean final weight, mean weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, apparent net protein utilization, and survival rate. The optimal performance was observed in fingerlings fed the diet containing 10% cassava peels, indicating that cassava peels can be a cost-effective alternative in the diet of Clarias gariepinus, potentially reducing feed costs for culturing this species.

What is the implication, and what should change now?

The implication of this study is that incorporating cassava peels into the diet of Clarias gariepinus can lead to improved growth and nutrient utilization, potentially reducing the cost of feed production for fish farmers. This finding suggests a need for further research and promotion of the use of cassava peels as a sustainable alternative feed ingredient in aquaculture. Policymakers and stakeholders in the aquaculture industry should consider supporting initiatives that promote the use of alternative feed ingredients like cassava peels, which can contribute to the sustainability and cost-effectiveness of fish farming operations.

The importance of fish as a valuable source of animal protein in human diets cannot be over emphasized [1].  Nutritionally, fish is about the cheapest and direct source of protein and micro nutrient for several millions of Africans [2]. Feed accounts for minimum of 60% of the total cost of fish production in African (Jamu and Ayinla, 2003) [3] and a major factor that determines the viability and profitability of fish farming enterprises. The expansion and intensification of aquaculture towards ensuring increase in food fish production in order to meet up with global demand since capture fisheries have continued to be on the decline over decades [4]. According FAO (2006) [5], fish supplies from capture fisheries will, therefore, not be able to meet the growing global demand for aquatic food.  Feeding is one of the essential functions of all organisms for the enhancement of growth, development and reproduction. All these activities take place at the expense of energy, which enters the organism in the form of its food [6]. Feed is one of the major inputs in aquaculture production and constitute over 60% of running cost and fish feed technology is one of the least development sectors of aquaculture particularly in Africa and other developing countries of the world [7]. High cost of fish feed was observed as one of the problems hampering aquaculture development in Nigeria [7]. The need to solve the problems of feeding in aquaculture has been demonstrated through various researches in the utilization of vegetable source and agricultural wastes such as plantain peel (Falaye and Oluruntunyi 1998) [8], poultry offal [6], maggot meal (Faturoti et al 1998) [9] have been emphasized in the formation of least cost of fish feed towards ensuring profitable fish business. Since fish farming like any other business is aimed at profit maximization and efforts aimed at reducing cost of feeding fish cannot be regarded as wasteful. This study is therefore aimed at utilizing the peels of cassava (Manihot esculenta) as energy source in the diet of Clarias gariepinus.

Experimental Site 

This study was carried out at the University of Agriculture Fish Farm, Makurdi, Benue State. The feeding trial was carried out for 8 weeks using hapas which were immersed in earthen pond.

Procurement of Fingerlings and Acclimatization 

Two hundred (200) fingerlings of Clarias gariepinus were obtained from reputable fish hatchery in Makurdi and were acclimatized for seven days before distribution into the various hapas.

Procurement and Processing of Feedstuff/ Ingredients 

The various feed stuff and ingredients such as fish meal, maize, mineral premix, vitamins premix, soybean, salt, oil were purchased from the market while cassava peel (Manihot esculenta) was obtained from a garri making industry at North Bank, Makurdi. The cassava peel (Manihot esculenta) was sundried to eliminate anti-nutritional factor such as cyanogenic glycoside before mixing it with other ingredients. Cassava peel contains cyanogenic glycosides, which can effectively be reduced by sun-drying, ensiling, fermentation, boiling and soaking and sun-drying [10].  Before the trial, diets were compounded, the feedstuffs were processed to improve digestibility and eliminate any anti-nutritional factor that may be present.

Diet Formulation 

Five experimental diets  were formulated using Pearson Square method at 35% crude protein for Clarias gariepinus while cassava peels were included at  different inclusion levels of  0(control), 2.5,  5,  7.5 and 10%. The gross composition of each diet is shown in Table 1. 

Experimental Set up and Management of Fish

The experimental design was completely randomized design with replicates. Ten hapas of 1x1x1m² were used and 20 fish were stocked in each hapas. The feed pellets were crumbled to particle size as 1.2-2.4mm as the appropriate sized range of fingerlings of Clarias gariepinus. The feed were administered to the fish twice daily at 10.00am and 4.00pm at 5% body weight. The fish were batch weighed weekly and feed intake adjusted accordingly.  All fish in each experimental unit were counted and weighed using the weighing balance. The hapas were washed each week to remove waste and the enhance water circulation. Water quality parameters such as temperature, pH, and Dissolved oxygen (DO) were checked.

Proximate Analysis

Proximate composition of the cassava peel used in this study was analyzed. Dry matter (DM), crude protein (CP), crude fibre (CF), ether extract (EE), ash were analyzed according to standard methods of AOAC (2005)

Estimation of growth performance, feed utilization and survival parameters

 The overall growth parameter and feed efficiency indexes were computed using the following equations (i) weight gain (%) = (final weight – initial weight) x (final weight) ^-1 x 100; (ii) daily weight gain (DWG) = (final weight – initial weight) x t^-1; (iii) feed conversion ratio (FCR) = (dry food fed) x (wet weight gain ) ^-1; (iv) specific growth rate (SGR; % day ^-1) = [Ln (final weight) – Ln (initial weight)] x (number of days)^-1 x 100 and (v) survival rate (SR; %) = (Total number of fish sampled) x (Total number of fish stocked)^-1 x 100.

Statistical analysis

Data were analysed as a design using the IBM SPSS statistics 22. Mean and one-way analysis of variance was performed to compare means. Duncan multiple range test was used to identify significant differences among different treatment means; P<0.05 was considered to be statistically significant.

RESULTS

The gross composition of cassava peel based diets is presented in Table 1. Nutrients for the formulated diets were all within the requirements for African catfish according to NRC (2011).

Table 1: The Gross Composition of Cassava peel based Diets.

Table 2 Shows the Proximate Composition of Cassava peel based diets fed to Clarias gariepinus

The crude protein content did not differ significantly (P˃0.05) and it ranged from 34.67 ±0.01 (Diet 5) to 35.01 ± 0.01 (Diet 4). Moisture content varied significantly (P˂0.05) with the highest value recorded in Diet 4 (7.92 ± 0.04) while the lowest value was recorded in Diet 1 (6.34 ± 0.09). Ash content differed significantly (P˂0.05) and it ranges from 8.45 ± 0.00 to 9.48 ± 0.09 with the highest value recorded in Diet 5 while the lowest was recorded in Diet 1. Ether Extract varied significantly (P˂0.05) with the highest value recorded in Diet 5 (6.93± 0.04) while the lowest value was recorded in Diet 1 (6.24 ± 0.01). Crude fibre content differed significantly (P˂0.05) and it ranged from 8.39 ± 0.06 (Diet 1) to 10.14 ± 0.02 (Diet 5) with the highest value recorded in Diet 5 while the lowest was recorded in Diet 1. Nitrogen Free Extract differed significantly (P ˂0.05) and it ranged from 30.65 0.15 (Diet 5) to 35.75 ± 0.22 (Diet 1).

Table 2: The Proximate Composition of Cassava peel based diets fed to Clarias gariepinus.

Means in the same row with different superscripts differ significantly (P<0.05)

Table 3 shows the Growth and Nutrient Utilization of Clarias gariepinus fed varying Level of Cassava peels. The mean initial weight (MIW) did not differed significantly (P˃0.05) for all the Diets but there was significant difference (P˂0.05) for the Mean final weight (MFW) and it range from 10.63 ± 0.32 (Diet 1) to 14.88 ± 0.58 (Diet 5). Mean weight gain (MWG) differed significantly (P˂0.05) with the highest value obtained in Diet 5 (8.43 ±0.058) while the lowest was obtained in Diet 1 (4.18 ±0.32). Similarly, Specific growth rate (SGR) varied significantly (P˂ 0.05) with the highest value recorded in Diet 5 (1.49 ± 0.07) while the lowest was recorded in Diet 1 (0.89 ± 0.05). Feed conversion ratio (FCR) differed significantly (P˂0.05) with the lowest value obtained in Diet 5 (4.46 ± 0.18) while the highest value was recorded in Diet 1 (6.83 ± 0.35). Also, Protein efficiency ratio (PER) varied significantly (P˂ 0.05) with the highest value recorded in Diet 5 (0.241 ±0.017) while the lowest value was recorded in Diet 1 (0.119 ± 0.009). Apparent net protein utilization (ANPU) also differed significantly (P˂0.05) and it ranged from 6.69±0.03 (Diet 3) to 8.71± 0.14 (Diet 2). Survival rate differed significantly (P˂0.05) and it ranged from 60.0% (Diet 4) to 77.50 ± 2.50% (Diet 1).

Table 3: Growth and Nutrient Utilization of Clarias gariepinus fed varying levels of Cassava peels based diets.

Means in the same row with different superscripts differ significantly (P<0.05)

Table 4: Proximate Composition of Initial and Final Carcass of Clarias gariepinus fed cassava peel based diets.

Means in the same row with different superscripts differ significantly (P<0.05)

Table 4 shows the Proximate Composition of Initial and Final Carcass Analysis. The crude protein content varied significantly (P˂0.05) and it ranged from 13.53 ± 0.01(Diet 1) to 14.24 ± 0.05 (Diet 2). The moisture content differed significantly (P˂0.05) and it ranged from 75.39 ±0.06 (Diet5) to 77.27 ±0.08 (Diet 1). Ash content varied significantly (P˂0.05) with the highest value recorded in Diet 1 (1.62 ± 0.04) while the lowest value was recorded in Diet 3 (1.20 ±0.01). Crude fibre content differed significantly (P˂0.05) and it ranged from 1.23± 0.01 (Diet 3) to 1.46 ± 0.02 (Diet 5) Ether extract varied significantly (P˂0.05) with the highest value recorded in Diet 1(1.83 ± 0.01) while the lowest value was recorded in Diet 5 (1.57 ± 0.03). Nitrogen free extract differed significantly (P˂0.05) and it ranged from 1.67 ±0.11 (Diet 4) to 6.02 ±0.01 (Diet 5). 

 Table 5 shows the weekly physico-chemical parameters of test solution are shown in Table 5. 

Table 5: Weekly Physicochemical Parameters during the Experimental Period

Means on the same column with different superscript are statistically different (P<0.05)

Figure 1 indicates the growth pattern of fish from the initial week (week 1) to the final (week 8). However, at the end of the week eight, diet 5 was observed to have a better growth pattern of Clarias gariepinus fingerlings than all the other Diets.

Figure 1: Weekly mean weight gain of Clarias gariepinus fed Cassava peel based diet.

The physico-chemical parameters of the water in the experimental tanks fall within the optimal ranges for optimum fish production [11]. The mean value obtained for the water quality parameter of the experiment shows that temperature (26.53 ±0.57), dissolved oxygen (4.41±0.10) and pH (7.45 ±0.13) fall within the optimal requirements for fish production.  This conformed to the report of Adikwu (1992), Anyanwu, (2003), Ochang et al., (2007), Madu et al., (2001).  [12-15]

The results obtained for proximate composition of cassava fed diets in this study was higher than the reports posited by Bichi and Ahmad (2010) [16] on proximate composition of cassava leaves. The difference may be attributable to the parts studied as well as processing methods. However, the proximate composition of the experimental diets fall within the range expected to support healthy growth of fish species [17].

From the result, all experimental diets were accepted by Clarias gariepinus fingerlings but the best growth rate was recorded for group of fish fed 10% inclusion of cassava peels in Diet 5 this might be attributed to the processing techniques used in processing the cassava peels which is drying.  Sun drying reduced the anti-nutrient of cassava peel and increased it palatability as reported by (Tewe 1992; Salami et al., 2003) [18,10] who reported that Cassava peel contains cyanogenic glycosides, which can effectively be reduced by sun-drying, ensiling, fermentation, boiling and soaking. In this study, higher level of mean weight gain (MWG) and specific growth rate (SGR) was obtained in Diet 5 containing 10% inclusion of cassava peel meal. This might be an indication that the nutrient were best converted to flesh by the fish in the diet and might be attributed to the acceptability and utilization of the feed. This followed similar trend with Omoregie et al.,(1991); Ugwu et al., (2004) [19,20] who recommended maximum inclusion rate of 10% for cassava peel meal in the diet of Nile Tilapia (Oreochromis niloticus). Olurin et al. (2006) [21] reported a replacement level of 50% cassava meal for maize without a depression growth in Clarias gariepinus.

The best Protein efficiency ratio (PER) was observed in Diet 5. This indicates that the energy to protein ratio was balanced and there was no sparing of protein for energy.  The lower feed conversion ratio (FCR) was obtained from Diet 5 which indicates better feed utilization by the fish fed Diet 5. According to De Silva and Anderson (2001) [22] feed conversion ratio is between 1.2 to 1.8 for fish fed carefully prepared diets, and the results from the present study fall within this range when multiplied by 10.

Survival rates recorded were different in all the Diets. The low survival rates recorded in the diets were attributed to handling stress and predators. This corroborates with the work of Attipoe et at., (2009) [23] who reported higher survival rate for Oreochromis niloticus and explained that mortalities during the experimental period were attributed to handling stress and predation.  Cardoso et al. (2005) [24] observed that good processing of cassava enhanced survival and healthy state of fish at all stages of their lives. The optimum survival rates recorded in this study indicate that feeding Clarias gariepinus catfish with processed cassava peels diet does not lead to mortality of the fish. This may probably be due to the substantial reduction in the cyanide content (by boiling and drying) of the cassava peels [25].

Satisfactory results on the use of cassava peel have also been reported on Nile Tilapia [20].  Cassava peel meal fed at dietary inclusion levels up to 30% to young Nile tilapia decreased performance (lower weight gain, productive protein value, feed efficiency and feed intake), and a maximum inclusion rate of 10% was recommended for feeding tilapia [19,20]. Contrastingly, Adewale (2013) [26] obtained good growth of Nile tilapia fed sun-dried cassava peels up to 15% dietary inclusion as total replacement for maize.

In conclusion, growth and nutrient utilization of Clarias gariepinus fed varying level of cassava peels increased with varying level of inclusion. It showed that Clarias gariepinus was able to effectively utilize up to 10% level of sundried cassava peels as dietary energy with increase in weight gain without reducing growth performance of fish. Clarias gariepinus performed optimally on diet containing 10% inclusion of cassava peels with respect to weight gain, specific growth rate, and protein efficiency ratio.

Recommendation 

From this research, it is recommended that sundried cassava peels could be included up to 10% to reduce cost of feed without necessarily compromising fish growth. This will boost fish production and also serve as means of utilization of waste resources such as cassava peels.

Funding: No funding sources 

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee of Bayero University

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