Improving health and disease resistance in common carp (Cyprinus carpio): The role of Saccharomyces boulardii and Lactobacillus rhamnosus and their combination

The present study was conducted to examine the impact of the dietary probiotic Lactobacillus rhamnosus (LR), Saccharomyces boulardii (SB) alone and combined, on immune responses, growth performance, and resistance against Aeromonas hydrophila in common carp (Cyprinus carpio) juveniles. Fish with initial weight of 7.78 ± 0.10 g were fed four experimental treatments. The treatments were presented as follows: T0: (control, without probiotics); T1: containing 10⁸ CFU/g L. rhamnosus; T2: containing 10¹⁰ CFU/g S. boulardii; T3: consisting of a combination of both (10⁸ LR CFU/g+10¹⁰ CFU/g SB), for 56 days. To investigate the disease resistance, the fish were subjected to A. hydrophila for 14 days following the feeding test. The probiotic groups alone or in combination revealed the best growth performance and the highest final weight, weight gain, and specific growth rate were noticed in the 10⁸ LR CFU/g+ 10¹⁰ CFU/g SB. The survival rate was higher for fish fed diets supplemented with probiotic versus control group. Notable increase was observed in superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX).The Malondialdehyde (MDA) level significantly decreased in probiotic supplemented treatments. Additionally, the probiotic treatment significantly increased the activity of digestive enzymes amylase, lipase, pepsin, protease, chymotrypsin, and trypsin. Furthermore, the probiotic supplementation improved a significant increase in immune related factors (Alternative complement activity, lysozyme, and total immunoglobulin) and genes (Interleukin-1 beta, Interleukin-6, Interleukin-8, Interleukin-10, and Tumor Necrosis Factor-alpha). The current findings indicated that the immune response and disease resistance in common carp are enhanced through the simultaneous application of L. rhamnosus and S. boulardii. This study recommends the simultaneous use of these probiotics to optimize their beneficial effects on the health of common carp.