Erythrocyte volume distribution in rainbow trout

Reference mean corpuscular volume and volume heterogeneity values for erythrocytes of 23 rainbow trout were measured, using an electronic particle counter, and were analyzed, using a particle-size analyzer and microcomputer. The mean (+/- SD) erythrocyte count was 1.5 X 10(6) +/- 0.16 X 10(6) cells/microliter, the mean corpuscular volume was 346 +/- 25 fl, and the mean coefficient of variation of erythrocyte volumes was 29 +/- 2.3%. All erythrogram curves were skewed to the right, representing a mean of 15.6 +/- 3.5% of the total cells counted.     

虹鳟鱼挤压膨化饲料研究

本文采用挤压膨化饲料作为试验组，硬颗粒饲料，小杂鱼作为对照组，对虹鳟鱼养殖效果和饲养成本进行分析，试验结果表明，试验组各项性能指标均优于对照组，且单位增重的饲料成本下降，说明用挤压膨化饲料代替硬颗粒和小杂鱼养殖虹鳟鱼，可获得较好的经济效益。     

Fin erosion on rainbow trout on commercial trout farms in the United Kingdom

Fish weighing less than 30 g and more than 100 g were sampled from 38 rearing units on 10 commercial farms growing rainbow trout for the table market. A fin index was calculated for each of the eight rayed fins on 949 trout by dividing their length by the standard length of the fish. There was a large range in the indices of all eight fins. The fin indices of the small and large fish were compared, controlling for farm effect. With the exception of the dorsal fin, all the indices were larger for the small fish than for the large fish, but the magnitude of the difference was greater for some fins than others. In comparison with the fins of wild fish, the pectoral and dorsal fins appeared to be most eroded and the damage to these fins was evident even in the small fish. The erosion of the caudal, anal and ventral (or pelvic) fins was more prominent in the larger fish. Variations in the fin indices of the caudal, anal and ventral fins suggested that there was little variation between rearing units on the same farm, but that there was significant variation between individual fish in the same rearing units, and between fish on different farms.     

Histopathological changes in myxosomosis in rainbow trout

Rainbow trout, caught in a pond 25, 45 and 48 days from releasing, were studied for histopathological changes. Protozoan activity destroys the basal matter of the hypertrophic cartilage. The chondral tissue around plasmodium reacts by showing an increased basophilia and by chondrocytal reaction. The plasmodia tend to spread spherically, but the spreading is prevented by compact bone, connective tissue, or hardened cartilage with flattened chondrocytes. One host can bear one plasmodium or more plasmodia, up to the possibility of a generalized process. The host organism reacts to the destructive changes caused by the protozoan by letting its connective tissue cells grow into the cavities produced by the protozoan, into the plasmodia of the protozoan and into the destruction line; thus the protozoan is separated from the nutrition base. The connective tissue enters the lesion via a hole in compact bone or via a fissure between bone and cartilage. Circulation and blood elements were not found to be present in the penetrating connective tissue. The bone tissue reacts to the presence of the protozoan by thickening the periosteum. Mature spores in the lesions by the protozoan are reduced with host age.     

Activation of rainbow trout complement by C-reactive protein

The activation of the complement system of rainbow trout by trout C-reactive protein (CRP) was investigated. Complement fixation tests were performed by using rabbit hemolysin-sensitized sheep erythrocytes and rainbow trout complement. Purified CRP increased the consumption of complement in the presence of Streptococcus pneumoniae C-polysaccharide (CPS), indicating the activation of the complement system. In contrast to this, acute phase serum activated the complement in the absence of CPS. Consumption of the complement by acute-phase serum was depressed when CRP was removed from acute-phase serum by CPS-sepharose 4B affinity chromatography. The acute-phase serum, as well as CRP plus CPS, suppressed in vitro growth of Vibrio anguillarum in the presence of complement, and enhanced the phagocytosis of the bacteria by glass-adherent peritoneal exudate cells. These results indicated that CRP has a role in host defense during acute-phase response through the activation of the complement system, enhancement of phagocytosis, and suppression of bacterial growth.     

脂肪软胶囊对虹鳟鱼生长影响的初步研究

试验研究了饲喂脂肪软胶囊对虹鳟鱼的生长和体成分的影响。试验共分4个处理组,每个处理组4个重复,每个重复8尾鱼。处理1组饲喂颗粒饲料,处理2组和处理3组在处理1组基础上分别另饲喂占颗粒饲料的30%和40%的脂肪软胶囊,处理4组饲喂进口高能膨化饲料。试验结果表明:与处理1组相比,处理2组显著提高了虹鳟鱼终末体重(P<0.05),处理3组也表现出提高的趋势,但差异不显著(P>0.05)。但与处理4组相比,处理2组(P>0.05)和处理3组(P<0.05)虹鳟鱼终末体重都下降。处理2组和处理3组虹鳟鱼增重率和特定生长率与处理1组相比都表现出提高的趋势,但差异不显著(P>0.05),与处理4组相比都显著下降(P<0.05)。处理1组和处理2组与处理3组和处理4组相比肥满度也显著降低(P<0.05)。与处理4组相比,其它处理组饵料系数也显著升高(P<0.05)。与处理1组相比,处理3组显著提高了体脂肪含量(P<0.05),降低了体水分含量(P<0.05),粗蛋白含量也提高(P>0.05)。其它处理组差异不显著,但处理2组和处理4组体脂肪也表现出明显的提高趋势,处理4组的体水分也表现出降低趋势。     

Immunization and culture of rainbow trout organ sections in vitro

Splenic and anterior kidney sections or whole organs were excised from large (1 kg) or small (200 g) rainbow trout (Salmo gairdneri) and placed in sterile 60 mm plastic plates containing 10 ml of Eagle's minimal essential medium (EMEM) supplemented with normal or fetal calf serum for in vitro culture. The organ samples were immunized in vitro by direct injection or by mixing in the medium Yersinia ruckeri O-antigen or dinitrophenyl-Ficoll. The medium was changed once during the 10-day incubation at 15 C. The passive hemolytic plaque assay demonstrated antibody production from the plaque-forming cells (PFC); passive hemagglutination was used to measure antibody titers in the media. High numbers of PFC occurred in cultures of either kidney or spleen, demonstrating that these organs can function independently for antibody production. Splenic sections from large fish produced more PFC than comparable whole organs from small fish. EMEM supplemented with 2% normal calf serum was a satisfactory culture medium. 2-hydroxyethyl-mercaptan an ingredient used in mammalian cell culture, inhibited antibody production in trout cells. These techniques are being used in the culture of organs and cells to elucidate pathways and sequences of antigen uptake and delivery of the immunopoietic tissues in trout.     

Residues of clenbuterol in tissues of the rainbow trout (Oncorhynchus mykiss)

There have been many studies on the efficacy of ₂-adrenergic drugs as feed additives but no data are available at present on the use of clenbuterol in fish production. To evaluate the residues of clenbuterol in tissues of fish, 50 trout (Oncorhynchus mykiss) were fed for 21 days on a fish feed containing 5 ppm of the drug. The livers, muscles and skins of sample groups of fish were analysed by HPLC with visible spectrophotometric detection on days 15 and 21 of treatment and at intervals during a 30-day withdrawal time. Clenbuterol reached its highest levels in the liver (mean 440 ppb; SD=±159;n=5) on day 15 of treatment, with a slow depletion curve; 24±3 ppb was still present at the end of the withdrawal period. At this time, residues were still present in the edible tissues, i.e. muscle (5±1 ppb) and skin (7±3 ppb). Side-effects were noted during the first week of treatment.Abbreviations ppb parts per billion - BHT butylated hydroxy toluene - CV coefficient of variation - DAD diode array detector - HPLC high-performance liquid chromatography     

Histopathological and electron microscopical observations on rainbow trout fry syndrome

Rainbow trout (Oncorhynchus mykiss) fry and fingerlings with clinical signs of rainbow trout fry syndrome, and rainbow trout (0.5 to 3.5 g) with experimentally induced infections with Flavobacterium psychrophilum, were examined histopathologically and electron microscopically. Severe hypertrophy of the spleen and cellular degeneration were consistently observed. Distinctive features of the disease were the loss of definition of the splenic border and its replacement by a loosely structured eosinophilic layer, fibrinous inflammation and intercellular oedema within the spleen, and the presence of numerous filamentous bacteria interspersed throughout the organ.