Diet supplemented with Grifola gargal mushroom enhances growth, lipid content, and nutrient retention of juvenile rainbow trout (Oncorhynchus mykiss)

Abstract

This study examined the suitability of the edible mushroom Grifola gargal as a dietary supplement for juvenile rainbow trout (Oncorhynchus mykiss). Three treatments were established in triplicate using 50 fish (0.33 ± 0.01 g) held in 50-L containers. Treatments consisted of feeds (42–45% protein, ca. 18% lipid) supplemented with fruiting-bodies of G. gargal at 0 g kg−1 (control diet (CTRL)), 25 g kg−1 (GG25), or 100 g kg−1 (GG100). Fish were hand-fed to apparent satiation twice a day (except on Sundays) for 56 days. Feed intake and growth were recorded throughout the study, and fish body proximate composition and nutrient retention were assessed at the end of the trial. Fish given GG25 diet had better growth and feed utilization than those given the other feeds. Final body weight was 2.37 ± 0.04 g (CTRL), 4.07 ± 0.07 g (GG25), and 1.94 ± 0.06 g (GG100) and the thermal-unit growth coefficient increased significantly from 0.64 ± 0.01 in CTRL to 0.87 ± 0.01 in GG25. The feed efficiency and the protein efficiency ratio were best for fish fed GG25, and body lipid was 42.3 ± 2.6 g kg−1 in CTRL and 75.3 ± 1.5 g kg−1 in GG25 treatments. This coincided with a lower viscerosomatic index in the fish given GG25 than in those provided with the other feeds. These results suggest that dietary supplementation with G. gargal at 25 g kg−1 enhances growth and leads to improved feed utilization in small rainbow trout.