Growth Performance, Gut Integrity and Intestinal Microbiome Responses of Juvenile Common Carp (Cyprinus carpio L.) to Probiotic and Prebiotic Supplementation

The aim of this study was to examine the impact of the probiotics <i>Saccharomyces cerevisiae</i> (SC) and <i>Pediococcus acidilactici</i> (PA), as well as the prebiotic yeast cell wall extract (<i>Cyberlindnera jadinii</i> and <i>S. cerevisiae</i>) (YP), on the growth parameters, intestinal histomorphology, liver and gills normality, and gut microbiome of common carp (<i>Cyprinus carpio</i> L.). These feed supplements were subjected to a 60-day experimental period, during which 120 fish (26.4 ± 5.2 g) were distributed into four groups, with each group comprising 30 fish. The feed supplements were administered at a rate of 1 g/kg of body weight. Before the trial, the fish were acclimatized for two weeks, then injected with Passive Integrated Transponder (PIT) tags. The results showed that none of the feed supplements exhibited a significant effect (<i>p</i> > 0.05) on growth indices. In contrast, the villi length, villi width, muscular thickness, and crypt depth in the anterior, mid, and posterior intestine of the SC group exhibited significant (<i>p</i> < 0.05) improvements compared to the other groups. No alteration or abnormal growth were noticed in the gills and livers. The most dominant microbe genera in all groups, with abundances greater than 60% of the total, were <i>Cetobacterium</i> and <i>Aeromonas</i>. However, <i>Polynucleobacter</i>, <i>Nordella</i>, <i>Mycoplasma</i>, <i>Romboutsia</i>, and <i>Staphylococcus</i> species were present at lower abundances. The presence of <i>Actinobacteria</i> has been observed only in the intestine of fish that have been fed a diet supplemented with PA. It can be concluded that the tested probiotics and the yeast cell wall prebiotic have the potential to produce a remarkable improvement in intestinal morphology and a considerable change in the gut microbiome without notable effect on growth, livers, or gills of common carp.