The effects of GroBiotic®-A supplementation on growth performance, body composition, liver and intestine histology in European seabass (Dicentrarchus labrax) juveniles were evaluated. The commercial GroBiotic®-A was added to diets at four different levels (0, 1, 2 and 3%), three replicates and fed 4 times a day (9:00, 11:30, 14:00, 16: 30 hours) for 60 days as ad libitum. Total 480 European seabass juveniles with a starting weight of 1.40±0.08 g were randomly stocked into 12 tanks with a volume of 1 m3. At the end of the study, the changes observed in weight, feed conversion ratios (FCR) and survival rates were calculated as 6.69 ± 5.35-7.40 ± 5.47, 0.80 ± 0.18-0.88 ± 0.20 and 96.6 ± 1.51-100 ± 0.0, respectively. When the body composition of the control and treatment groups were compared, no statistically significant differences were observed between the protein and lipid values (p>0.05), except ash (p <0.05). Histological sections of intestinal tissue; the number of goblet cells was higher than that of the control group. The highest values were determined in the group supplemented 2% GroBiotic®-A. The highest microvillus length was found in the group added 1% GroBiotic®-A. It was detected an inverse relationship between microvillus length and contribution rates as the the GroBiotic®-A additive levels increased. Also, degeneration and necrosis was detected in hepatocyte cells of seabass juvenile fed with diets supplemented 2% and 3% GroBiotic®-A as well as increase of the number of fatty vacuoles in liver tissue due to the increase in the amount of GroBiotic®-A. In conclusion, when the growth parameters, body composition and histological data were evaluated together, the feeding group supplemented 1% GroBiotic®-A performed the best.

This study, it was aimed to examine the clinical, hematological, and histopathological aspects of lactococcosis induced in European sea bass (Dicentrarchus labrax), which was experimentally infected with Lactococcus garvieae. For this purpose, the infection was induced intraperitoneally with L. garvieae strain (108 CFU/mL), and blood samples were collected from the infected fish on different days (6, 18, 26, 31, 36, 44, and 48th) of infection. The morphological structures, erythrocyte and leukocyte count, hematocrit value, sedimentation rate, and coagulation time of the blood cells in the collected samples were calculated. As a result of the infection, while there was a decrease in erythrocyte count, hematocrit value, and coagulation rate, in addition to changes in the morphological structure of blood cells, it was determined that there was a significant increase in the leukocyte count and sedimentation rate. Furthermore, histopathological examination was also performed in the organs of infected fish such as the brain, liver, spleen, kidney, heart, gill, and intestine. Histopathologically, in the infected sea bass, while hemorrhage, diffuse necrosis, and hyaline droplets were detected in the granular brain tissue, hyperemia and hemorrhage were noted in the liver and spleen, and widespread necrosis in the hematopoietic tissue of the kidney, in the gills intensive hyperplasia, an increase in the goblet cell were detected. Although there are studies on lactococcosis in various marine fish species around the world, the infection of L. garvieae in farmed sea bass and various parameters and pathological aspects were investigated in detail for the first time in this study. L. garvieae was determined to have clinical significance for European sea bass with a high economic value.

The aim of this study was to diagnose the bacterial pathogens of moribund rainbow trout (Oncorhynchus mykiss) reared in a dam-lake cage farm located in the Black Sea Region of Turkey and to determine their antibiotic susceptibility and histopathological effects by using routine bacteriological, histopathological and molecular methods. Besides possibility of the use of two probiotics against these pathogens for the prevention of further infections was investigated. In this study, a mixed bacterial infection case caused by Frigoribacterium faeni and Lactococcus garvieae was diagnosed in rainbow trout samples of 100-250 g with general clinical and histopathological symptoms of bacterial hemorrhagic septicemia. Pathogens were found to be resistant against most of the antibiotics tested and the possibility of the use of Bacillus subtilis as a probiotic to prevent diseases caused by these pathogens was proposed.

The prolonged starvation has many effects on the physiological and morphological processes in fish and interferes them with the ability to absorb nutrients and caloric intake. The aim of present study was to investigate the effect of long-term starvation and posterior dietary administration of commercial synbiotic consisting fructoligosaccharide (FOS) which used in combination with Enterococcus, Lactobacillus, Bifidobacterium and Lactococcus spp. for evaluation on some blood biochemical parameters and histological characteristics of common carp liver. Experimental fish after 5 months starvation period were subjected to the following feeding protocols: continuous starvation until 60 day (ST), re-feeding (FS) with dry composed diet (Aqua 1032 Swim) and refeeding with composed diet and synbiotic (FSS) for the following 60 days. Blood samples were used for analysis of the following plasma parameters: total protein, albumin, globulin, urea, creatinine, cholesterol, AST, ALT, glucose and serum for thyroid hormones. Histology analyses were performed on the carp liver samples. During the experimental period, fasting and refeeding were influenced significant on studied biochemical parameters, except glucose and urea. Also, the statistically largest ( P <0.001) difference was observed in albumin and cholesterol values after refeeding. Our results reveal the changes in values of biochemical parameters during long-term starvation and refeeding with synbiotic and indicate signs of structural alterations of the liver in common carp.

Identifying pathogenic microorganisms causing disease is important for epidemiological research, antimicrobial therapy, and control. The current study was carried out to use different methods for the identification of Vibrio anguillarum from diseased rainbow trout (Oncorhynchus mykiss) obtained from Türkiye (Muğla-Fethiye), the damage caused by the pathogenic microorganism in the tissues and organs, and the determination of the antibiotic effective against the pathogen. Hemorrhagic and ulcerative skin lesions and diffuse petechial hemorrhage in the internal organs were clinically detected in diseased fish obtained from the rainbow trout farm. Bacteria isolated from diseased fish were subjected to analysis using conventional bacteriological methods, a commercial bacterial identification test kit (API), an automated bacteria identification system known as Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), BD Phoenix™, and 16S rRNA sequence analysis. All isolated bacteria were identified as V. anguillarum by API 20E and conventional bacteriological method. These results have been confirmed with 16S rRNA sequence analysis. However, the isolated bacteria were identified as Grimontia hollisae (syn. Vibrio holisae) with the BD Phoenix system. Histologically, tissue damage such as melano-macrophage centers and necrosis in the kidney and spleen, hyperemia and mononuclear cell infiltration in the liver, as well as mononuclear cell infiltration on muscles, talengectiasis in the gill tissue was observed. In addition, it has been determined that the most effective antibiotic against the pathogen was enrofloxacin. When comparing all identification methods used for this pathogen causing tissue damage, it was demonstrated that the MALDI-TOF MS provides better results than other methods in terms of cost and identification time, and it could be used as an alternative to the conventional method to the identification of V. anguillarum.