Head kidney-derived macrophages activity and survival rate in yellowtail (Seriola quinqueradiata) after oral administration of maitake (Grifola frondosa) fruiting body powder.

Abstract

In a long-term consecutive administration study for 311 days at an aquaculture site, we considered the possibility of application of an oral immunostimulant of maitake (Grifola frondosa) fruiting bodies (maitake powder) to yellowtail (Seriola quinqueradiata). The cumulative fish mortality was significantly reduced by administration of maitake powder (approximately 45 mg/kg body weight/day) compared with the untreated control (P < 0.05). Fish administered maitake powder were also superior in body weight gain to the untreated control though the difference was not significant, and feeding efficiency was similar between the groups. Phagocytic activity was significantly stimulated by maitake powder administration compared with the untreated control (P < 0.05). We also performed a follow-up study on immunostimulation by maitake powder, with consecutive administration of the powder at a dosage of 48.5-mg or 91.6-mg/kg body weight/day for 28 days in an interior water tank test. The phagocytic rate was significantly improved by maitake administration compared with the untreated control at days 7, 14 and 28 (P < 0.01). The above results indicate that maitake powder is useful for improvement of mortality in yellowtail aquaculture through immunostimulation of macrophages.