Dry feed for Artemia: its effect on performance, physiology, immune responses and bacterial resistance

The larviculture of fish and shellfish is inevitably dependent on live food such as Artemia and one of the most important issues in rearing Artemia is the food supply. Artemia culture is mainly dependent on freshly prepared unicellular algae, which is not accessible easily. This research focused to prepare a dry feed that can support the survival and growth of Artemia and improve its resistance against pathogenic bacteria. The nauplii of Artemia were fed seven feeding treatments, including the control diet (algae + yeast) and six experimental dry feed containing different levels of probiotic bacteria. The results showed that Artemia fed a diet containing 10% algae+1.25% probiotic bacteria performed slightly better in terms of growth, but significantly higher survival and increased alkaline protease activity was detected compared to control. The lipase activity was significantly higher only in Artemia fed 5% algae + 0.625% probiotic bacteria, and the highest Amylase activity was detected in the control group. The activity of the antioxidant enzymes superoxide dismutase (SOD), Glutathione reductase (GRed), Glutathione peroxidase (GPx) and Malondialdehyde (MDA) presented a significant increase as a function of culture time and probiotic administration. The challenge with the pathogen resulted in significantly higher survival in all tested life stages of Artemia (nauplii, juvenile, and adults) in negative and positive controls compared to the control diet group. It is concluded that pathogen induces an oxidative stress response in almost all stages of Artemia growth and probiotic bacteria Bacillus coagulans and B. subtilis protects Artemia when challenged with Vibrio anguillarum by enhancing immune responses.