Evaluation of dietary fish meal analog with or without supplementation of natural feed additives as the substitute of fish meal in juvenile Japanese eel, Anguilla japonica

• Published in: Frontiers in Marine Science Vol. 9
• Main Authors: Bae, Jinho, Lee, Seunghyung, Moniruzzaman, Mohammad, Hamidoghli, Ali, Choi, Wonsuk, Lee, Seunghan, Min, Taesun, Kim, Shin-Kwon, Bai, Sungchul C.
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 22-07-2022
• Subjects: feed additives; fish meal; fish meal analog; growth; hematology; innate immunity
• ISSN: 2296-7745; 2296-7745
• DOI: 10.3389/fmars.2022.931940

We investigated the nine experimental diets containing fish meal (FM) and/or fish meal analog
(
FMA) as the major source of animal protein to determine the optimum FMA level as the substitute of FM protein in the diet of juvenile Japanese eel. In addition, two natural feed additives such as Song-Gang stone (SG) and Yucca meal (YM) were supplemented in the diet to evaluate their efficacy as the immunostimulants. The diets are as follows: 100% FM + 0% FMA in diet (FMA
0
), 90% FM + 10% FMA in diet (FMA
10
), 80% FM + 20% FMA in diet (FMA
20
), 70% FM + 30% FMA in diet (FMA
30
), 60% FM + 40% FMA in diet (FMA
40
), FMA
0
+ 0.4% SG (FMA
0
SG), FMA
0
+ 0.1% YM (FMA
0
YM), FMA
20
+ 0.4% SG (FMA
20
SG), and FMA
20
+ 0.1% YM (FMA
20
YM). Nine groups of Japanese eel each with three replicates were distributed (initial weight of 9 ± 0.2 g) in rectangular tanks receiving flow through water. Each group of the treatment consisted with 15 fish and fed one of the diets for 8 weeks. At the end of the feeding trial, fish fed with the FMA
0
and FMA
10
diets showed no significant differences in weight gain (WG), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER). Meanwhile, fish fed with FMA
20
, FMA
30
, and FMA
40
diets showed significantly lower WG, SGR, FE, and PER than the fish fed with the FMA
0
(control) diet. In addition, there were no significant differences among fish fed with the SG- and YM-supplemented diet groups. However, lysozyme activities in fish fed with the FMA
10
, FMA
20
, FMA
30
, and FMA
40
were significantly lower than the fish fed with the FMA
0
SG, FMA
0
YM, FMA
20
SG, and FMA
20
YM diets. After 7 days of injection with
V. Anguillarum
, cumulative survival rates of fish fed with the FMA
0
SG and FMA
0
YM diets were significantly higher than the FMA
0
diet group. The results revealed that the FMA could replace up to 10% of FM as a protein source in the diet of Japanese eel and both of the natural feed additives (SG and YM) could improve replacing rates of FMA from 10% to 20% without compromising growth and health status of fish.