DETERMINATION OF GROWTH PERFORMANCE AND FEED UTILIZATION OF FRY OF GOLDFISH, CARASSIUS AURATUS (ACTINOPTERYGII: CYPRINIFORMES: CYPRINIDAE) FED L-CARNITINE-SUPPLEMENTED DIETS

Determination of growth performance and feed utilization of fry of goldfish, Carassius auratus (Actinopterygii: Cypriniformes: Cyprinidae) fed l -carnitine-supplemented diets. Acta Ichthyol. Piscat. 50 (3): 349–356. Background. A quest continues for alternative feed additives to the content of feeds used in global ornamental fish farming. This study was initiated to see the effect l -carnitine on the growth, feed utilization, and survival rates of goldfish, Carassius auratus (Linnaeus, 1758), one of the most cultivated aquarium fish species in the world. This experiment was carried out since there was no previous study on the effect of the l-carnitine on goldfish. Materials and methods. In this study, five isonitrogenous, isolipidic, and isoenergetic diets (40% protein, 6% lipid, and 14.82 MJ · kg –1 digestible energy, respectively) were formulated. The diets were supplemented with l -carnitine at the dose of 250, 500, 750, and 1000 mg · kg –1 with a non-supplemented diet as control. Goldfish fry was reared in a 65 L glass tank containing aged water. Each dietary treatment was tested in triplicate groups of 20 fish per glass tank. Experimental fish (0.311 ± 0.01 g initial weight) were fed the diets twice daily to apparent satiation for 84 days. In the experiment, diets were evaluated based on growth performance and diets utilization. Results. Supplemental dietary l-carnitine has beneficial effects on improving growth performance, feed conversion ratio, specific growth rate, and protein efficiency ratio in goldfish fry. Conclusion. This study provides first data on the effect of l -carnitine on growth, feed utilization, and survival rates of goldfish. Future research should focus on the growth performance, and feed utilization parameters of other ornamental fish of different conditions of l -carnitine supplemented diets.


INTRODUCTION
In recent years, the importance of global ornamental fish farming and trade is increasing day by day. All species of goldfish in trade in the world has reached a volume of more than 1 billion dollars annually in more than 125 countries. (Anonymous 2016). These fish are one of the most preferred fish species by people, because of their varieties and attractive colors, and high tolerance to environmental effects. For this reason, it is very important for the ornamental fish farming that goldfish can reach the market size in a short time by feeding with low-cost feed. (Gümüş et al. 2016).
If l-carnitine is defined simply, it can be explained as amino acid and vitamin-like nutrient elements associated with B-group vitamins. It is an essential element mainly involved in the conversion of fatty acids into energy. In another definition, l-carnitine is not exactly an amino acid, because it does not work in protein synthesis. However, it is said to be grouped under this title because of its similarity with amino acids (Bremer 1983, Shigenaga et al. 1994. l-carnitine is synthesized from lysine and methionine in a way dependent on iron and ascorbate. l-carnitine provides the passage of fatty acids through the mitochondria membrane. It is necessary for the transfer of long-chain fatty acids through the membrane (He andDahl 2000, Harpaz 2005).
The addition of l-carnitine in fish feeds plays an important role in promoting growth, the protein-protective effect of fat, and ultimately reducing fat accumulation in the body (Harpaz 2005, Yang et al. 2009).
Many studies are aiming to use l-carnitine in fish nutrition, involving the following fish species, silver perch, Bidyanus bidyanus (Mitchell, 1838) (see Yang et al. 2012 This study was intended to investigate the effects of l-carnitine on feed consumption, live weight increase, survival, and feed evaluation of goldfish, Carassius auratus, which is one of the most cultivated goldfish species in the world. We assumed that our study would be useful since no research publication related to feeding to l-carnitine supplemented feeds for goldfish fry, has been available. The fry is one of the most important stages of goldfish cultivation.

MATERIAL AND METHODS
Preparation of feeds. The diets to be used in the experiment were prepared based on fish meal and soybean meal. They contained 40% crude protein and represented 14.65 MJ · kg -1 of digestible energy, as defined by Yanar et al. (2008) and Silva et al. (2010) as the nutritional requirement of goldfish. For the experiment, feeds with the mean digestible energy content of 40% crude protein, 6% crude lipid, and 14.65 MJ · kg -1 were formulated (Table 1). The feed of the experimental groups was prepared by formulating in five different ways, including the ratios of 0, 250, 500, 750, and 1000 mg · kg -1 of l-carnitine. The nutritional content has been verified and the results are shown in Table 2.
Experimental conditions. This study was carried out in a laboratory of the Faculty of Fisheries Research, Akdeniz University. Experimental fish were obtained from the Kepez Unit of the Ministry of Agriculture and Forestry Mediterranean Fisheries Research Production and Training Institute. The fry had fed and adapted to new conditions in 250 L fiber-glass for two weeks. At the end of the two weeks, goldfish fry with the mean live weight of 0.311 ± 0.01 g and a total length of 2.68 ± 0.04 cm were placed randomly in 15 aquaria, with 20 fry per tank. In the study, 15 glass aquaria (65 L) (70 × 30 × 40 cm) were used. The experiment was carried out with 3 replications. During the experiment, the lighting was set with fluorescent light for 10 h at day (0800-1800 h) and 14 h at night (1800-0800 h). Aquarium water was heated with thermostat heater at 24°C and aerated with stone aquarium diffuser. All groups were fed by hand, two times a day (0800 h and 1700 h) for 84 days until they were satiated. The unused feed and the fish feces accumulated on the bottom of the tank were removed by siphoning one hour after the last feeding of the day. The amount of water decreased by siphoning in the experiment tanks was completed with aged water (approximately 1/3). Water temperature, pH, and dissolved oxygen were measured daily using the WTW multi-oxygen meter (WTW Wissenschaftlich- Table 1 Composition of diets used in the l-carnitine feeding experiment on Carassius auratus l-carnitine contents where W F is the final weight, W I is the initial weight, T is time [days], L T is the total body length, N F is the final fish number, N I is the initial fish number. The weight and length values are expressed in grams [g] and centimeters [cm]. The feed utilization values, such as feed conversion ratio (FCR) (Halver and Hardy 1982) and protein efficiency ratio (PER) (de Silva and Anderson 1994) were calculated according to the following equations: where I F is the feed intake [g], and I P is the protein intake [g]. Chemical analysis. Chemical analysis of experiment feeds was done according to the rules of the AOAC (Association of Official Analytical Chemists) (Anonymous 1995). For the determination of a matter, the samples representing each group were weighed and taken into moisture containers. Then they were kept in the oven for about 12 h until they reached a constant weight in the oven set at 105 ± 2ºC and then they were left in the desiccator to cool down to room temperature. The crude protein analysis was carried out using the Kjeldahl method. Crude lipid analysis was determined by ether extraction with the help of the Soxhlet extraction system. The ash analysis was made by burning the samples in the ash oven at 550°C (Anonymous 1995). Statistical analyses. The statistical evaluation of the data obtained from the experiment was made using the SPSS 15.0 (SPSS INC. Chicago, IL, USA) package program. After applying variance homogeneity tests to all data, variance analysis (ANOVA) was performed to determine the effect of different l-carnitine ratios on weight and length. Duncan multiple comparison tests was applied to see differences in weight, height, specific growth rate (SGR), condition factor (CF), feed conversion ratio (FCR), and protein efficiency ratio (PER) between the groups.

RESULTS
Growth values of the experimental fish fed different feeds are given in Fig. 1. There were statistically significant differences between the weight increase values of the fish in the experiment groups (P < 0.05). As the l-carnitine level increased, an increase in weight values was observed. It was determined that the group fed feed containing 1000 mg · kg -1 l-carnitine was the best in terms of an increase in weight.
Growth values of experimental fish fed different feeds are given in Fig. 2. Statistically significant differences were found between the growth values of fish in the experimental groups (P < 0.05). As the l-carnitine level increased, an increase in growth values was observed. It was determined that the group fed feed containing 1000 mg · kg -1 l-carnitine was the best in terms of an increase in length.
Condition factor values of the experimental fish fed different feeds are given in Fig. 3. There were no statistically significant differences between the condition factor values of the fish in the experimental groups (P > 0.05). It was determined that the group fed feed containing 750 mg · kg -1 l-carnitine had the best condition factor.
The specific growth rate values of the experimental fish fed different feeds are given in Fig. 4. Statistically significant differences were found between the specific growth rate values of fish in the experimental groups (P < 0.05). It was Table 2 Proximate composition of diets used in the l-carnitine feeding experiment on Carassius auratus (%, wet weight)

Composition of diets [%]
Diet 0 Values represent the mean value ± standard deviation of three replicate analyses; l-carnitine contents in diets [mg · kg -1 ]: Diet 0 = 0, Diet 1 = 250, Diet 2 = 500, Diet 3 = 750, and Diet 4 = 1000; determined that the group fed feed containing 1000 mg · kg -1 l-carnitine had the best specific growth rate. Feed conversion ratio values of the experimental fish fed different feeds are given in Fig. 5. Statistically significant differences were found between the feed conversion ratio of fish in the experiment groups (P < 0.05). It was determined that the group fed feed containing mg · kg -1 l-carnitine had the best feed rate.
The protein efficiency ratio values of the experimental fish fed different feeds are given in Fig. 6. Statistically significant differences were found between the protein efficiency ratio values of the fish in the experiment groups (P < 0.05). It was determined that the group fed feed containing 1000 mg · kg -1 l-carnitine had the best feed rate.  Fig. 3. Condition factor values of Carassius auratus used in the l-carnitine feeding experiment (Different letters indicate statistical significance at 95% confidence interval)
In our study, the survival rate of fish was 100%. We believe that the reason for such a high survival rate might be the following factors a short experimental period, low stocking density, and adherence to hygienic requirements.

CONCLUSION
Supplemental dietary l-carnitine has beneficial effects on improving growth performance and feed conversion ratio in goldfish fry. When the level of l-carnitine supplement dietary increased, there was an increase in weight and length growth values, condition factor, and specific growth rate. Future research should focus on the growth performance and feed utilization parameters of other ornamental fish of different conditions of l-carnitine supplemented diets.