On the 23rd of September 2022, a small intensive aquaculture unit populated with rainbow trout (Oncorhynchus mykiss) reported increased mortality in adults and juvenile fish. The unit comprised 12 enclosed concrete basins with a capacity of ten cubic meters of water, populated with 150 kg of fish each. Fish were subjected to a clinical examination on the site, after which whole fish were harvested for a bacteriological and histopathological examination. Water quality parameters were examined using classic biochemical methods and Fourier Transform Infrared Spectroscopy in order to find out whether the environment in which the fish live is also a predisposing factor that could facilitate different pathogens and induce a state of disease in the fish. Real-time PCR was performed on strains of Aeromonas spp. sampled from the fish to accurately identify the pathogen species. The goal was to accurately identify the problems and predisposing factors that lead to disease outbreaks.

Aquaculture faces numerous challenges related to fish health. To explore new solutions, the objective of this study was to test the effects of wheatgrass juice (WGJ) as feed supplement on growth performance, blood biochemical profile, bacteriological balance, and oxidative stress in common carp (Cyprinus carpio). Carp fingerlings (8.8 g initial body weight) were fed diets containing 4% or 8% WGJ in a recirculating aquaculture system for eight weeks. Most growth performance parameters did not differ significantly among dietary treatments, although the viscerosomatic index (VSI) was significantly lower in WGJ-supplemented groups. WGJ supplementation was associated with changes in oxidative-status parameters, including increased antioxidant enzyme activities and reduced malondialdehyde levels, particularly at the 8% inclusion level. Blood biochemical parameters showed no evidence of adverse effects on liver or kidney function. Total protein, globulin, and albumin did not differ significantly among treatments. Microbiological examination highlighted a decrease in pathogenic bacteria, including sulfite-reducing clostridia, with a 4% WGJ diet showing the most pronounced inhibitory effects. These results indicate that WGJ supplementation may influence selected biochemical, oxidative-status, and cultivable intestinal bacterial parameters in common carp. Further studies are required to determine the underlying mechanisms and the practical relevance of these effects.