Program and Abstracts(PDF)

Poster presentation 17
EFFECTS OF DIFFERENT SUPPLEMENTATION LEVELS OF EXTRACTED SOY
PEPTIDE ON GROWTH PERFORMANCE AND TOLERANCE TO HIGH
TEMPERATURE STRESS IN JUVENILE JAPANESE FLOUNDER, PARALICHTHYS
OLIVACEUS
Janice A. Ragaza 1* , Roger Edward Mamauag 1 , Yoshinori Sotoyama 2 , Saichiro Yokoyama 2 ,
Manabu Ishikawa 2 , and Shunsuke Koshio 2
1
United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima 890-
0056, Japan
2 Laboratory of Aquatic Animal Nutrition, Faculty of Fisheries, Kagoshima University,
Kagoshima 890-0056, Japan
* Email: janice_a_ragaza at yahoo.com
The experiment was designed to examine whether different supplementation levels of
extracted soy peptide (SPEP) to soy protein concentrate (SPC) diet could improve growth
performance, amino acid body composition, and tolerance to high temperature stress in
juvenile Japanese flounder (Paralichthys olivaceus). Four isonitrogenous and isolipidic SPC
diets and one fishmeal (FM) diet (positive control D1) were prepared with increasing SPEP
supplementation levels of 0% (D2), 2% (D3), 5% (D4), and 10% (D5), respectively. Triplicate
groups of twenty juveniles (1.29±0.01 g, mean ± SD) were stocked in 100-L polypropylene
tanks and were fed twice a day to apparent satiation level for 42 days.
The present study demonstrated that fish fed D5 grew faster than those fed diets 2, 3, and 4,
respectively, although growth was significantly lower in fish fed D5 than that in fish fed D1.
The feed conversion ratio and protein efficiency ratio showed the same trend as that of growth
performance, but feed intake was not significantly (P > 0.05) different among diets. Except
for some amino acids, whole body total and free amino acid compositions of flounder were
not altered by SPEP supplementation in the diets.
In the lethal heat stress test, fish fed D5 demonstrated the highest value of LT 50 , which was
significantly (P < 0.05) longer than that of fish fed other diets. Furthermore, LT 50 values of
fish fed diets D3 and D4 were significantly (P < 0.05) longer than fish fed D1. Heat shock
protein 70 family (HSP70s) was highest in the gill, liver, and skin of fish fed D5, which was
significantly (P < 0.05) higher than that of fish fed other diets after sub-lethal stress exposure.
Moreover, HSP70s values of fish fed D3 and D4 were significantly (P < 0.05) higher than fish
fed basal and control diets. Time-course sub-lethal heat shock exposure results demonstrated
that level of HSP70s significantly (P < 0.05) decreased among all groups during recovery
period, but did not return to normal and initial state after 24 hours.
Based on the overall performance of the fish, SPEP can be efficiently absorbed and utilized by
flounders, but more than 10% supplementation might be needed to catch up the performance
of fishmeal based diet in the condition applied in this study.
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