Nutritional Characteristics of Eels (Auguilla japonica) Fed a Diet of Yuza (Citrus junos Sieb ex Tanaka)

Abstract

The study investigated the effect of diets supplemented with different levels (0 and 2.5%) of yuza (Citrus junos Sieb ex Tanaka) on the nutritional characteristics of eels (Auguilla japonica). Fish (9.8±1.3 g) was fed to apparent satiation twice daily for 8 months. There were no significant differences in proximate composition among the treatment groups, except for the ash and carbohydrate contents (P<0.05). The vitamin C content of eel muscle in the yuza-added group was two-times higher than in non-added groups (P<0.05). Among eight organic acids in eel muscle, lactic acid was predominant, followed by citric acid, oxalic acid, malic acid, and acetic acid. Eels fed a 2.5% yuza diet had the highest lactic acid content in all groups. Six sugars were found in all groups and glucose was the major sugar. Glucose and maltose were the dominant sugars in the yuza-added group. The abundant fatty acids in the yuza-added group were C18:1 n-9, C16:0, and C16:1 n-7, which comprised over 80% of the total fatty acids. The major amino acids in samples were glutamic acid, aspartic acid, lysine, and leucine. There were few differences in the free amino acid compositions among the groups. However, histidine was the predominant amino acid and constituted over 53% of the total free amino acids.

Comparison of Major Nutrients in Eels Anguilla japonica Cultured with Different Formula Feeds or at Different Farms

“…In addition to price increases for A. japonica elvers, overall changes to eel culture, such as increases in the cost of raw materials for formula feeds (FFs), labor costs, and various expenses, have maintained constant pressure on eel farmers. In response, researchers have examined the use of FFs with no or reduced amounts of fish meal; how to lower the mortality rate; the development of functional feed additives; the application of high-density culture; and the relationships between rearing tank size and stocking density, between body weight and stocking density, and between body weight and daily feeding rate (Bae et al, 2008;Choi et al, 2008;Hwang et al, 2010;Son et al, 2011).…”

Nutritional Characteristics of Black Rockfish (Sebastes schlegeli) Fed a Diet of Fish Skin

“…Analyzes of proximate composition, fatty acid, total amino acid, free amino acid, organic acid, and free sugar in this study were carried out based on AOAC methods [23] and some modifications of Hwang et al [24].…”