Bromelain is a proteolytic enzyme extracted from Ananas comosus and has great potential
to affect several physiological functions. The current study examined the effect
of bromelain added to commercial feed at concentrations of 0 g (control), 10 g
(B1) and 20 g (B2) per kg diet on growth, feed utilization, intestinal morphology,
digestive enzyme and immune response of juvenile Sterlet (Acipenser ruthenus) for
56 days. At the end of this experiment, the highest final body weight was detected in
fish fed diet of B2 compared to control. The protein content of whole fish was higher
in fish fed diet of B1 and B2, but the content of calcium, iron, copper and zinc was
noted lower in fillets of fish fed diet of B1 and B2. Supplementation with bromelain
significantly increased the height of mucosal folds, enterocytes and the supranuclear
zone of the epithelial cells compared to control diet. The enzymatic activity of lipase
and pepsin was significantly (p < 0.05) higher in fish fed diet of B1 and B2. The highest
activity of lysozyme, total protein level and total immunoglobulin and the proliferative
activity of T and B cells were detected in fish fed diet of B2 compared to control,
where no significant (p > 0.05) difference was found in ceruloplasmin, metabolic
activity of spleen macrophages and potential killing activity of spleen phagocytes
between different treatments.