INOSINE SUPPLEMENTATION EFFECTIVELY PROVOKES THE GROWTH, IMMUNE RESPONSE, OXIDATIVE STRESS RESISTANCE AND INTESTINAL MORPHOLOGY OF JUVENILE RED SEA BREAM, Pagrus  major

Md. Sakhawat Hossain*, Shunsuke Koshio, Manabu Ishikawa, Saichiro Yokoyama,  Nadia Mahjabin Sony,  Manabu Usami, Sayoko Ono, Takeshi Fujieda
 
*The United Graduate School of Agricultural Sciences,
Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan
fishsakhawat@yahoo.com

Inosine, a purine nucleoside containing the base hypoxanthine and the sugar ribose, which occurs in transfer RNAs. Inosine is considered as a functional nutrient. In aquaculture inosine has been studied most extensively as a specific nucleoside for feeding stimulation research rather than using as a functional nutrient for potential growth and health benefit of aquatic species. Red sea bream (Pagrus major), is one of the most economically cultured marine fish species in Japanese aquaculture, due to its economic feasibility and traditional food habits. Lately, the aquaculture of this species has also developed rapidly and widely in China, and Korea. Effects of inosine nucleoside as a functional nutrient of this species are not reported elsewhere. Therefore, a feeding trial was conducted to determine the effect of dietary inosine as functional nutrient on growth performance, immune responses, oxidative stress resistance and intestinal morphology of juvenile red sea bream. A semi purified basal diet supplemented with 0% (D1, control), 0.2% (D2), 0.4% (D3), 0.6% (D4) and 0.8% (D5) dietary inosine respectively to formulate five experimental diets. Each diet was randomly allocated to triplicate groups of fish with initial average weight of approximately 8 g.

After 50 days of feeding trial, fish fed diets with 0.4% inosine had the highest (P<0.05) final weight, % weight gain and specific growth rate. Similarly, improved (P>0.05) feed intake, feed conversion ratio, protein efficiency ratio were also found at 0.4% inosine supplemented group. Some non specific immune parameters such as serum lysozyme activity, total serum protein, bactericidal activity tended to be higher for fish fed diets supplemented with inosine while peroxidase activity significantly influenced by dietary inosine supplementation. Whole body proximate composition and somatic parameters were not influenced (P>0.05) by the dietary treatments except in hepato somatic index where, 0.4% inosine supplemented diet showed significantly higher (P<0.05) values than the control group. A wide variation in some of the blood parameters was observed. In case of oxidative stress parameters, fish fed 0.2% and 0.4% inosine supplemented diets showed best condition because of the least oxidative stressed condition as well as the highest tolerance against oxidation.  In terms of intestinal health condition, supplementation of inosine increased anterior enterocyte height and posterior fold height, enterocyte height and microvillus height significantly compared to control. Anterior fold height and microvillus height also increased with inosine supplementation compared to control but not at a significant level. Considering overall performance we concluded that, dietary supplementation of 0.4% inosine effectively provokes growth and health performance of red sea bream by increasing growth, immune response, oxidative stress resistance and intestinal health condition.