Utilization of Skipjack tuna (SJT) offal (Katsuwonus pelamis) on growth of juvenile koi carp (Cyprinus carpio) Abstract

The effects of skipjack tuna (SJT) offal (Katsuwonus pelamis) on growth performance of juvenile koi carp (Cyprinus carpio) were studied for 42 days. Two isonitrogenous (416.6 kg g-1) and isocaloric (2.02 kcal g-1) diets were prepared by using SJT offal and marketed fish meal with lipid levels (dry matter) of 6.93 ± 0.03% (mean± SD). A total of 900 juvenile fish (Cyprinus carpio) averaging 0.58 ± 0.03 g (mean ± SD) were randomly distributed in nine square cement tanks, and each tank was randomly assigned to one of three replicates of three diets containing

36% fish meal (FM) (T1), and 8% FM and 32% SJT offal powder (T2) with commercial diet (T3). After 42 days, weight gain (WG), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed T2 were significantly higher than those of fish fed T3 (P<0.05). Even though no significant difference was seen in WG, FE and PER of fish fed T1 and T2, and; T1 and T3. However there were no significant differences in final weight (FW), specific growth rate (SGR), and survival among fish fed three different diets (P>0.05). Although significant differences were not recorded in proximate composition fish fed experimental diets. The total cost for T1 and T2 feeds were 210 and 155 (Sri Lankan Rupees (LKR)) respectively while commercial feed was available for 180 (LKR). The results indicate that the SJT offal could be utilized cost effectively as a protein supplement in juvenile koi carp feeds to replace high cost fish meals.

Introduction

The ornamental carp, Cyprinus carpio var. koi L. is very popular to fish hobbiset throughout the world. Currently highest operational cost (more than 60%) goes for feeds in ornamental fishculture practices in the world. Recently it leads to minimize the profit in aquaculture practices in the world even practical feeds are being utilized. Pelleted feeds have been traditionally based on fish meals (FM) and fish oils (FO), derived from industrial feed–grade fisheries of small pelagic species such as anchovies, sardines, herrings and mackerel. The reduction fisheries have, at best, reached their sustainable limit and over past 30 years, around 20-25 million tons of feed fish have been caught annually, which reduce to about 6-7 Metric tons of FM and 1-1.4 Metric tons of FO (NRC, 2011). There is no realistic prospect of FM and FO production being increased in the future and, indeed there is increasing competition for these small pelagic species for human consumption (Tacon and Metain, 2009a). Land animal products such as blood meal, meat meal, feather meal, bone meal and poultry by products meal are mostly comparable substitute for FM because their amino acid compositions are more similar to FM than most plant products. But they are highly variable in terms of nutritional content (NRC, 2011). Therefore researchers from all over the world have put great efforts in identifying alternative protein sources that would allow a reduction in feeding costs (Portz and Cyrino, 2004). Nowadays, the use of food wastes as animal feed is an alternative of high interest, because it stands for environmental and public benefit besides reducing the cost of animal production (Samuels et al., 1991; Westendorf et al., 1998; Myer et al., 1999; Westendorf, 2000). Records show that millions tons of fish waste are dumped to the sea in many parts of the world. Food industry wastes are an important environmental contamination source. Research has been carried out in order to develop methods to convert these wastes into useful products (Perea et al., 1993; Kristinsson & Rasco, 2000; Larsen et al., 2000; Guerard et al., 2001; Coelloet al., 2002; Laufenberg et al., 2003). Probably, more than 50% of the remaining material from the total fish capture is not used as food and involves almost 32 million tonnes of waste (Kristinsson &

Rasco, 2000; Ioannis and Aikaterini, 2008). Offal from the fishing industry could be used as a feed ingredient, as it represents a valuable source of high-quality protein and energy (New, 1996; Gabrielsen & Austreng, 1998). Kotzamanis et al. (2001) studied the

potential utilization of trout offal as an ingredient of gilthead bream (Sparus aurata, Sparidae) (L.) diets. And they observed that trout waste could be used successfully as a dietary ingredient of sea bream diets. Therefore this study was aimed to identify the effects of Skipjack tuna (SJT) offal as a feed ingredient on growth of Koi carp and the potential to substitute expensive imported fish meals by giving a solution to SJT waste in Sri Lanka. Materials and Methods Diets and Experimental design Two experimental diets were formulated to contain 36% fish meal (FM) (T1), and 8% FM and 32% SJT offal powder (T2) (Table 1), and each diet was randomly assigned to triplicate groups. Table1. Composition of experimental diets (% of DM basis) Diets1 Ingredients T1 T2 T3 Fish meal2 36 8 - Skip Jack tuna waste3 0 32 - 2 Soybean meal 24 24 - Meat meal2 1 1 - Coconut meal4 5 5 - Rice bran5 6.5 6.5 - Maizemeal2 1 1 - Wheat flour2 20 16.5 - Fishoil2 5 4.5 - Vitamin mineral premix2 1.5 1.5 - Total 100 100 - Proximate composition6 Moisture 6.8 5.00 9.69 Energy7 2009.49 2030.68 1995.68 Crude protein 41.65 41.94 41.40 Crude lipid 7.73 7.84 5.22 Crude ash 13.28 17.54 8.14 1 T1, control: T2, contains dried skip jack tuna offal powder; T3, commercial diet 2Supphaiah feed suppliers, Wolfendhal Street, Colombo 13, Sri Lanka 3Central fish market, Peliyagoda, Sri Lanka 4Anura rice mill, Ambilipitiya, Sri Lanka 5Nipuna Coconut oil mill, Ambilipitiya, Sri Lanka 6Results mentioned on % of DM basis 7Results mentioned on calories per gram (cal/ g) Fish and feeding trial Feeding trial was conducted at the ornamental fish breeding center, National Aquatic Resources Research and Development Agency (NARA), Sri Lanka. Koi carp juvenile fish were procured from Carp breeding center, Ginigathena, Sri Lanka. Feeding trial was performed in an outdoor, refilling fresh water tank system for 42 days. Initial average weight of 0.57±0.03 g (mean ±SD) juvenile Koi fish were randomly allocated in 9 cement tanks of 1.5 m ×1.2 m × 0.20 m. Triplicate tanks per each diet group were used by 100 fish per tank. Fish were acclimatized for the culture system and feeds for a week after allocation. Initially, the fish were fed at 7% of biomass and divided in to 3 meals (09:00, 12:00, and 17:00) everyday. But later it was adjusted according to body weight as 5 % and 4 %. Water temperature, pH and dissolved oxygen level of the system was maintained at 26.2 ± 0.4 °C, 8.3 ± 0.13, 4.9 ± 0.7 mg∙L-1, respectively. Data collection and sample analysis Weight of three samples consisting 20 fish per each sample was taken from each tank separately after every 2 weeks. Fish were starved 12 hours before weighing. Percent weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER) and survival rate were calculated as described in Table 2. Proximate composition analysis of fish and experimental diets were performed by standard method of AOAC (2000). Statistical analysis One-way analysis of variance tests (ANOVA) was used to analyze the calculated WG, FE,PER, SGR and Survival Rate data. Least significant difference (LSD) was used to find the treatment effect at P<0.05 level of significance using Statistical Analysis System (SAS Institute Inc. 2000). Results During feeding trial, all the experimental diets were well accepted by fish. After 42 days of feeding trial, there were significant difference in weight gain (WG), feed efficiency

(FE) and protein efficiency ratio (PER) among fish fed T2 and T3 diets. But no significant differences were observed in WG, FE and PER among fish fed T1 and T2; and T1 and T3. Moreover no significant differences were observed in survival rate, final weight (FW) and specific growth rate (SGR) among fish fed T1, T2 and T3. Growth performance values were shown in Table 2. Table2. Growth performances of juvenile koi carp fed three experimental diets for 6 weeks1 Diets2 Pooled

10 T1 T2 T3 SEM IW3 0.54 0.57 0.59 0.01 FW4 1.25 1.35 1.23 0.03 WG5 129.3ab 137.29a 108.62b 4.97 SGR6 0.76 0.78 0.51 0.06 FE7 30.79ab 32.69a 25.86b 1.18 PER8 0.72ab 0.77a 0.61b 0.03 Survival (%)9 96 97 96.7 0.29

1Values are mean from triplicate groups of fish where the values in each row with different superscripts are significantly different (P<0.05). 2See Table 1 3IW: Initial weight (g/fish). 4FW: Final weight (g/fish). 5WG: Weight Gain (%) = (final weight - initial weight) × 100 / initial weight.

6 -1 SGR: Specific Growth Rate (% day ) = (loge final wt.-loge initial wt.)/days 7FE: Feed Efficiency (%) = weight gain (wet) (g) × 100 / feed intake (dry) (g). 8PER: Protein Efficiency Ratio = weight gain(wet) / protein intake. 9Survival (%): (total stocked fish-dead fish at the end) x100/ total stocked fish 10Pooled SEM: Pooled Standard Error of Means: SD/√n. Discussion The present study showed the potential of SJT waste meal for inclusion of juvenile Koi carp diets. Several studies have been reported that fish meal in fish diets can be replaced by plant protein sources as well as comparatively less studies have been explained to replace by fish waste hydrolysates, fish silage and fish offal. Buyukcarpar and Kamalak (2007) found that hazelnut meal can replace up to 35% of protein in fish meal and 40% of protein in soybean meal in fingerling mirror carp diets without adverse effects on growth performance, feed utilization and body composition. Utilization of Skipjack tuna waste as a dried powder has been observed as a good alternative for high value fish meal varieties by this study. Significant differences in WG, FE and PER have been observed when comparing with commercially available manufactured carp feed. Furthermore offal from the fishing industry could be used as a feed ingredient, as it represents a valuable source of high-quality protein and energy (New, 1996; Gabrielsen & Austreng, 1998). Kotzamanis et al. (2001) studied about the potential utilization of trout offal as an ingredient of gilthead bream (L.) diets. Moreover they cited that the growth and body composition data from this preliminary experiment indicated that trout waste could be used successfully as a dietary ingredient of sea bream diets. Conclusion The study revealed that the SJT offal could be utilized cost effectively as a protein supplement in juvenile Koi carp feeds to replace high cost fish meals.

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