Effects of dietary galactooligosaccharide on growth, antioxidants, immunity, intestinal morphology and disease resistance against Aeromons hydrophila in juvenile hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂)

The present study investigated the effects of dietary galactooligosaccharide (GOS) supplementation on growth, antioxidant capacity, immunity, intestinal morphology and resistance to Aeromons hydrophila of hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂). A total number of 360 fish were randomly distributed into 12 aquaria and fed diets supplemented with GOS at 0%, 1%, 3% and 5% concentrations (designated as control, GOS1, GOS3 and GOS5) for 8 weeks. Then 30 fish from each group were intraperitoneally challenged with A. hydrophila, and mortality was recorded for the next 15 days. The results showed that there were significant differences of final body weight (FBW), weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR) in sturgeon fed GOS diets. The lysozyme, ACP, AKP and MPO activities in sturgeon serum fed GOS diets were higher than those with control diet. Significant increase of SOD, CAT and GSH-PX capacity and remarkably decrease of MDA content were observed in liver of fish fed GOS diets. Remarkable enhancement of muscular thickness, villus and microvilli height, and goblet cells in mid intestine was observed in GOS supplemented groups. In spiral valve, supplementation of any quantities of GOS promoted an evident increase in the muscular thickness, villus height and goblet cells, while the villus width and crypt depth were relatively invariant. The IL-1β and IL-8 mRNA levels were decreased and TNF-α gene expression was increased by dietary GOS. The challenge test with A. hydrophila resulted in lower mortalities by GOS administration in a dose-dependent manner and the highest relative percent survival (36.67 ± 1.92%) was observed in fish fed GOS5 diet. The study concludes that GOS inclusion at the rate of 3% is recommended to increase the growth performance, antioxidant capability and immunity as well as regulate intestinal morphology and promote resistance against A. hydrophila in hybrid sturgeon.