Effects of Poly-β-hydroxybutyrate (PHB) and PHB degrading bacteria (Acidovorax sp.) on the growth performance, body composition and bacterial metabolic activity in Siberian Sturgeon (Acipenser baerii) fingerlings

Five hundred and ninety two Siberian sturgeon fingerlings (average weight, 11.1±0.9 g) were randomly distributed in 16 tanks (150 L) at a density of 35 fish per tank and fed different treatments (Control, degrading bacteria, 2% PHB, degrading bacteria + 2%PHB) for 60 days. At the end of the experiment, no significant difference was observed in case of final weight in fingerlings but fish fed PHB and degrading bacteria had lower FCR then the others (P<0.05). Also dietary treatments affected on the lipid percentage in fish muscle and lowest lipid content was observed in supplemented diets (P<0.05). The bacterial metabolic activity of fingerlings hindgut was investigated by biological oxygen demand (BOD5) method using Oxitop® bottles and the results showed that the highest bacterial metabolic activity was seen in fish fed PHB. Also, at the end of the BOD test, bottles pH was measured and the results indicated that the lowest pH was observed in PHB and degrading bacteria treatments. The results in this experiment show that PHB and degrading bacteria have beneficial effects on growth performances and bacterial metabolic activity of Siberian sturgeon fingerlings. Such effects could be considered for new applications in aquaculture.