Aquaculture America 2021

August 11 - 14, 2021

San Antonio, Texas


Sungchul C. Baia,b* ,Jinho Baea* , Ali Hamidoghlia ,  Wonsuk Choia, Ji young Kimc  and  Sera Choid
aDepartment of Marine Bio-materials and Aquaculture/ Feeds and Foods Nutrition Research Center, Pukyong National University, Busan 48513, Republic of Korea
bFAO World Fisheries University Pilot Program, Pukyong National University, 365, Sinseon-ro, Nam-gu, 48547, Busan, Republic of Korea.
cCJ R&D, Gwanggyo-ro 42 beon-gil 55, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16495, Korea
dCJ BIO, 330, Dongho-ro, Jung-gu, Seoul, 100-400, Korea

Two experiments were conducted to evaluate the dietary micro-algae, schizochytrium sp. as a fish oil (FO) replacer in rainbow trout, Oncorhynchus mykiss .

Exp.1: Seven diets were formulated to replace FO at 0% (CON), 20% (T20), 40% (T40), 60% (T60), 80% (T80) and 100% (T100) by using schizochytrium sp., and 38% of commercial Micro algae (CMA) diet. Triplicate groups of 20 fish averaging 3 ± 0.4g (mean ± SD) were fed one of seven experimental diets. After the 8 weeks of feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER) of fish fed T20 diet were significantly higher than those of fish fed the other diets (P <0.05). Fish fed CON had higher WG, SGR, FE, PER than those of fish fed T100 and CMA diets. Superoxide dismutase (SOD) activity of fish fed T20 and T40 diets were significantly higher than those of fish fed CON diet. Lysozyme activity of fish fed T20 diet were significantly higher than those of fish fed the other diets (P<0.05). For 10-days challenge test with pathogenic bacteria ( Lactococcus garvieae 1x108 CFU/ml), cumulative survival rate of fish fed T20 diet were significantly higher than those of fish fed CON, T80, T100 and CMA diets.

Exp.2:  Apparent digestibility coefficients (ADCs) of dry matter, crude protein and crude lipid in various feed ingredients including schizochytrium sp. were determined for rainbow trout. The ingredients consisted of fishmeal, soybean meal, poultry by-product meal, schizochytrium sp. produced by CJ Inc. and  commercial micro algae. A reference diet with 0.1% Cr2O3 as the inert marker was mixed with test ingredients in a 7:3 ratio to produce a series of test diets. Fish were fed their respective diets and fecal samples were collected by stripping. ADC of ingredients of protein and lipid for rainbow trout ranged from 86.7-98.0% and 24.6-55.3%, respectively. ADC for protein of fishmeal was significantly higher than those of schizochytrium sp. (P <0.05). However, schizochytrium sp. had significant higher ADC  for protein than other ingredients (P <0.05). ADC of schizochytrium sp. were significantly higher than other ingredients (P <0.05).

Therefore, it could be concluded that Schizochytrium sp. can replace FO up to 80% without any negatively influence on growth, non-specific immune responses and disease resistance in rainbow trout. A lso, schizochytrium sp. could be a feed ingredient as the lipid source in rainbow trout.