Dietary effects of two commercial feed additives on growth performance and body composition of African catfish Clarias gariepinus fingerlings

An experiment was conducted to evaluate the effect of two commercial feed additives on growth, nutrient utilization and body composition of African catfish, Clarias gariepinus fingerlings. Two commercial feed additives Aqua booster ® and Aqua pro ® were added to the basal diet at 0.5 g kg −1 feed and fed to the fish for 56 days at 3% body weight. Fish fed on diets with commercial feed additives showed significantly improved growth performance, feed utilization and body composition compared to fish fed on the control diet. The best growth was observed in the group fed with dietary Aqua pro ® . The protein efficiency ratio (2.73 ± 0.58) and specific growth rate (9.13 ± 0.60) were significantly higher in groups fed with the Aqua pro ® diets. The highest protein content (67.15%) was obtained in the fish fed with dietary Aqua pro ® and it was significantly higher than in all other groups (p<0.05). Moisture content did not differ among treatments. Ash and lipid contents were significantly affected by feed additives. The results revealed that using Aqua pro ® at level of 0.5 g kg −1 feed was the best in terms of growth performance and feed utilization.


INTRODUCTION
Over the years, the total world fishery production decreased slightly and the human consumption for aquatic product increased (FAO, 2010).The reduction in capture fisheries was partly compensated for the fast growth of aquaculture industry.The need for enhanced disease resistance, feed efficiency and growth performance of cultured organisms is substantial for various sectors of this industry (EL-Haroun et al., 2006).If growth performance and feed efficiency are increased in commercial aquaculture, the costs of productions are likely to be reduced.There is large number of feed additives available to improve fish growth performance in the Nigeria markets and some of these additives used in feed mill are chemical products especially hormones and antibiotics which may cause unfavourable side effects.World Health Organization encourages using of medicinal herbs and plants to substitute or minimize the use of chemicals through the global trend to go back to nature.Attempts to use the natural materials such as medicinal plants could be widely accepted as feed additives to enhance efficiency of feed utilization and aquaculture productive performance.Recently, medicinal plants and probiotics have been reported as potential alternatives, among other feed additives, to antibiotics in aquaculture diets.Much of this interest arises from increased public awareness and banned to the use of antibiotics as growth promoters in aquaculture diets.In the last decade, some studies show the positive effects of dietary medicinal *Corresponding author.E-mail: dadaayokanmi@yahoo.com.plants and feed additives on growth and feed utilization in fish (Turan and Akyurt, 2005;Turan, 2006;Soosean et al., 2010;Deng et al., 2011;Farahi et al., 2011;Dada and Oviawe, 2011;Prasad and Mukthiraj, 2011;Cho and Lee, 2012).The African catfish Clarias gariepinus is widely cultured in Nigeria under intensive management (Adewolu et al., 2009).Increased production of fry and fingerlings with attributes of faster growth rates and higher environmental tolerance is sine qua non to ensuring fish food security in Nigeria.Aquaculture requires high quality feeds which should contain not only necessary nutrients but also complementary feed additives to keep organism's healthy, faster growth and environmental friendly.The main objective of this study was to investigate the effect of using two commercial feed additives (Aqua booster ® and Aqua pro) on growth, feed utilisation and body com-position in African catfish (C.gariepinus) fingerlings.

Formulation of experimental diets
Commercial feed additives (Aqua booster ® and Aqua pro ® ) were obtained from a chemical store in Akure, Nigeria.0.5 gkg -1 of the feed additives were mixed with a basal feed comprising standard amounts of fish meal, yellow maize, soybean meal, blood meal, fish oil, vegetable oil, vitamin premix and starch, formulated using pearson square method (Table 1).All dietary ingredients were milled to a 3 mm particle size.The ingredients were thoroughly mixed in a Hobbart A-2007 pelleting and mixing machine (Hobart Ltd, London, UK) after which the experimental diets were pelleted with a laboratory pelleting machine with a 0.9 mm die and dried at ambient temperature (27 to 30°C).Experimental feeds were stored at deep-freezer (-20°C) until used.Proximate composition of experimental diets were determined according to AOAC methods (2005): dry matter (DM) after drying in an oven at 105°C until constant weight; crude protein (N = 6.25) by Kjeldahl digestion and distillation after acid digestion; crude lipid by petroleum ether extraction in a Soxtec apparatus; ash by incineration in a muffle furnace at 550°C for 8 to 12 h (Table 2).

Experimental procedure
Nine glass aquaria tanks (2 × 2 × 1.5 m), each half-filled with water were aerated continuously using an air compressor.Ninety farmraised C. gariepinus fingerling (with an average initial weight of 7.27 to 7.52 g) were acclimated to laboratory conditions for 14 days before being distributed randomly into the nine tanks (10 fish tank -1 ) representing two dietary treatments (0.5 gkg -1 of feed additives) respectively and a control (0 gkg −1 of feed additive).Fish were fed at 5% of their body weight (bw) per day in three equal meals, every 5 h between 08:00 and 18:00.All fish were weighed and counted fortnightly and feeding rates were adjusted accordingly.At the end of the experimental period, the following growth and feed utilization indices were calculated: weight gain (WG), specific growth rate (SGR), food conversion ratio (FCR), feed efficiency (FE) and protein efficiency ratio (PER) using the following formulae: WG = Final average weight (g) − initial average weight (g); Where Wt and W0 represent final and initial body weights of fish, respectively, and t represents the duration of the feeding trial; FCR = Dry weight of feed (g) / wet weight gain by fish (g); and PER = wet weight gain by fish (g) / protein intake (g) Where protein intake (g) = Protein (%) in feed × total weight (g) of diet consumed / 100 Water temperature, pH and dissolved oxygen concentration were routinely monitored in all tanks.At the beginning and end of the feeding trial, pooled samples of 15 fingerlings were analyzed for carcass composition according to AOAC methods (2005): dry matter (DM) after drying in an oven at 105°C until constant weight; crude protein (N = 6.25) by Kjeldahl digestion and distillation after acid digestion; crude lipid by petroleum ether extraction in a Soxtec apparatus; ash by incineration in a muffle furnace at 550°C for 8 to 12 h (Table 3).

Statistical analyses
Analysis of variance (ANOVA) was used at 95% significance level to test for significant differences between the various treatment means obtained for the growth, feed utilization and carcass composition using the SAS package.Tukeys multiple range test was used to determine which pairs of the treatment means differed significantly.

RESULTS
Mean water quality parameters during the experiment were: dissolved oxygen 6.40 ± 0.19 mg l -1 , pH 7.24 ± 0.13 and temperature 27.10 ± 0.33°C.There were improvements in the growth responses of fish fed on dietary feed additives.The fastest growth responses were obtained in the fish fed on dietary Aqua pro ® (9.13 ± 0.60) while the slowest growth was obtained in the fish fed on the control diet (8.01 ± 0.60) (Table 4).There were significant differences in growth performance across the different dietary feed additives.There were greater improve-ments in the feed conversion ratio (FCR) of fish fed on dietary feed additive than the control fish.The average FCRs were 0.86 and 0.83 for diets Aqua booster ® and Aqua pro ® , respectively.The PER was 2.53 and 2.73 for the fish fed diets Aqua booster ® and Aqua pro ® , respectively.Fish fed on dietary feed additives had a significantly (p < 0.05) higher protein content than fish fed the control diet.The body composition values are given in Table 3.

DISCUSSION
Water quality parameters were not significantly different between treatments and were within the recommended ranges for the culture of C. gariepinus (Viveen et al., 1986).The results suggest that dietary feed additive promoted the growth of C. gariepinus fingerlings.These results showed that feed additive enhances nutrient utilization, which is reflected in improved weight gain, FCR, PER, PE and SGR.Generally, better feed conversion ratio values were obtained in all treatments, but the poorest occurred in control (Table 4).There were significant differences in the FCR among the treatments (p < 0.05).Aqua superliv ® in diets also promoted growth and feed conversion efficiency in Nile tilapia fingerlings (Dada, 2012).Similar results were reported for using two different commercial feed additives for Nile tilapia fingerlings (Abdelhamid and Mohammed, 2008).EL-Haroun (2007) also reported that African catfish fingerlings fed on diets supplemented by commercial feed additive Biogen® exhibited faster growth than those fed with the control diet.Similarly, in catfish C. gariepinus (Turan and Akyurt, 2005), tilapia Oreochromis niloticus (Khattab et al., 2004;Felicitta et al., 2013), olive flounder Paralichthys olivaceus (Cho and Lee, 2012) and shrimp Peneaus indicus (Olmedo Sanchez et al., 2009) feed additives in diets promoted growth and feed efficiency.From a proximate composition point of view, feed additives increased the level of protein in C. gariepinus.
The body composition values obtained in this study were similar to those reported by Diab et al. (2002), Lara-Flores et al. (2003) and Abdelhamid and Mohamed (2008) using commercial feed additives.Interestingly, we found that the survival of C. gariepinus can be improved by feed additives supplementation.Therefore, we expect that this result will stimulate a series of studies on the utilization of these two commercial feed additives in diets for fishes.

Conclusion
This study established the efficacy of Aqua booster ® and Aqua pro ® feed additives as a growth promoter in C. gariepinus fingerlings and fish farmers should be encouraged to supplement these feed additives in fish diet.Future research should focus on the improvement of rearing technologies for different species of fish reared using feed additive as a feed supplement.

Table 1 .
Ingredients and proximate composition of the experimental diets.

Table 2 .
Chemical analysis (% on DM basis) of the experimental diets.

Table 3 .
Chemical composition of whole body of C. gariepinus fingerlings fed experimental diets.

Table 4 .
Mean growth performance and feed utilisation of C. gariepinus fingerlings fed experimental diets for 56 days.Means in a given column with the same superscript letter were not significantly different at p < 0.05.SGR, Specific growth rate; PER, protein efficiency ratio; FCR, feed conversion ratio. b