Can dietary ethanolic extract of propolis alter growth performance, digestive enzyme activity, antioxidant, and immune indices in juvenile beluga sturgeon (Huso huso)?

Abstract

The present study investigated the effects of dietary ethanolic extract of propolis on growth performance, digestive enzyme activity, liver antioxidant capacity, and skin mucus immunity in beluga sturgeon. For this purpose, a total of 120 juvenile fish (595.55 ± 31.61 g) were distributed in 12 tanks and fed with ethanolic extract of propolis at 0, 1, 2, and 3% for 60 days. The current study results showed that growth indices and the survival rate did not change in the juvenile fish fed with this extract compared to the control group. However, the protease activity, pepsin, and chymotrypsin were significantly higher in beluga sturgeon fed with the treated diet than the control fish (P < 0.05). The results also showed a higher white blood cell count in fish provided with 2 and 3% extract than in the control group (P < 0.05). The level of the alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase activities in the fish liver remained unaffected in all groups (P˃0.05). Meanwhile, the activities of antioxidant-related enzymes were significantly higher (P < 0.05) in the liver of beluga sturgeon fed with dietary ethanolic extract of propolis, especially at 3%, than the control fish. In 2 and 3% treated groups, the skin mucus of beluga sturgeon showed an enhanced lysozyme activity and total immunoglobulin level (P < 0.05) compared to the control group. In parallel, the in vitro assay revealed an elevated serum antibacterial activity against Aeromonas hydrophila in the fish fed with 2 and 3% extract compared with the control group (P < 0.05). It can be concluded that the supplementation of ethanolic extract of propolis, especially at 3%, could improve some digestive enzyme activities, liver antioxidant capacity, and skin mucus immunity of juvenile beluga sturgeon.