Effects of fermented chamomile on hematological and immunological parameters and gut health in common carp, Cyprinus carpio

IntroductionThis study aimed to determine the effects of fermented chamomile, Matricaria chamomilla L., meal (FCM) supplementation on growth performance, hematological parameters, antioxidant defense system, gut microbiota, and gene expression levels in common carp, Cyprinus carpio.MethodsFish were fed four experimental diets containing 0 (0-F), 7 (7-F), 14 (14-F), and 21 (21-F) g/kg FCM for 60 days.Results and discussionThe results showed that, except for final weight, all measured parameters exhibited significant quadratic responses to dietary FCM levels. Weight gain, specific growth rate (SGR), and intestinal superoxide dismutase (SOD) activity were significantly higher in the 7-F group compared to the 0-F group. Red blood cell (RBC) count, hematocrit, hemoglobin, white blood cell (WBC) count, neutrophil percentage, plasma bactericidal activity, and the intestinal abundances of Lactobacillus sp. and Bacillus sp. were significantly higher in the 7-F and 14-F treatments than in the 0-F group. In contrast, blood lymphocyte percentage, intestinal malondialdehyde (MDA) levels, and the expression of intestinal kelch-like ECH-associated protein 1 (keap1) and nuclear factor kappa B (nf-κb) were significantly lower in the 7-F and 14-F groups compared to the 0-F group. Feed efficiency, intestinal glutathione peroxidase (GPx) activity, mucus bactericidal activity, and the expression of intestinal nuclear factor erythroid 2-related factor 2 (nrf2) and heat shock protein 70 (hsp-70) were significantly higher in all FCM-supplemented groups compared to the 0-F group. Conversely, the intestinal abundances of Aeromonas sp. and Vibrio sp., as well as the expression of interleukin-1 beta (il-1β) and tumor necrosis factor-alpha (tnf-α), were significantly lower in all FCM-treated fish than in the 0-F group. Overall, the greatest improvements compared with the control were observed in the 7-F treatment, followed by the 14-F treatment, across most evaluated parameters. These findings suggest that FCM, particularly at a dietary inclusion level of 7 g/kg, may serve as a promising functional feed additive in common carp nutrition and contribute to improved fish health.