Health and disease status of Thai pangas, Pangasius hypophthalmus cultured in rural ponds of Mymensingh, Bangladesh

Thai pangas, Pangasius hypophthalmus is one of the important aquaculture species in Bangladesh. Over the last few years spectacular development has been taking place in Thai pangas farming in Mymensingh district. Due to availability of easy breeding and culture techniques as well as quick return, more and more people are converting their rice fields into pangas farms overnight. The present study was carried out to examine health and disease status of Thai pangas mainly through clinical, histopathological and bacteriological techniques. In addition, for collecting primary data on disease and health status of Thai pangas and the resultant socioeconomic impacts on rural households, questionnaire interview and participatory rural appraisal tools were used with selected farming households in three upazilas of Mymensingh district. The most prevalent diseases as reported by the farmers were red spot, followed by anal protrusion, tail and fin rot, pop eye, dropsy and gill rot. Other conditions like cotton wool type lesion, ulceration and white spot were reported but with lower incidence. Four isolates of Aeromonas hydrophila were recovered from kidney and lesion of diseased fish. Hemorrhage over the body especially near mouth and caudal region was noticed in the fishes associated with aeromonad infection. Internally, kidney, liver and spleen became swollen and enlarged. The isolates varied with their pathogenicity. All the four isolates were sensitive to Nitrofurantoin, Cotrimoxazole and Tetracycline but were resistant to Amoxycilline. An attempt was made to treat diseased fish with extracts from neem leaf, garlic and turmeric. Recovery of infection was monitored through mortality and histopathology. General histopathological changes of different organs were also studied. Extract from neem (Azadirachta indica) leaf gave better result. Telangiectasis, lamellar hypertrophy and hyperplasia hemorrhage, lamellar fusion, necrosis of lamellar epithelial cells, presence of parasites and their cysts were the major pathology of gills. Hemorrhagic lesion, pyknotic nuclei and melanomacrophage centers (MMC) were found in the liver of fish. Major pathologies in kidney of fish included presence of MMC, necrotic and ruptured kidney tubules, severe haemopoietic necrosis, and hemorrhage. The economic loss due to disease in Thai pangas farming was estimated from the difference between expected production and actual production. On an average, Thai pangas farmers of Mymensingh incur a loss of Tk. 23,104/ha/cycle due to fish disease (3.6% of expected total production). The loss, however, varied with location and size of farms, type of farmers and management practices. The study also highlighted fish health management related problems and recommended further work for the development of user-friendly farmer-oriented fish health management packages.

The effect of vitamins C and E on some of growth factors of cultured Acipenser ruthenus

The effect of vitamins C and E on some of growth factors of cultured Acipenser ruthenus was studied in this thesis. For this purpose diets supplemented with a combination of 100 and 400 mg/kg vitamin C, L-ascorbyl-2-polyphosphate and 100 and 400 mg/kg vitamin E, D-alpha-tocopherol,were each fed to sterlet in 2 replications for 15 weeks. Fifteen fish with average weight of 350.92±14.28 gr were distributed to each of 18 tanks after adaptation with experimental diet. After 5 weeks, there were significant differences in RBC, ESR, HCT and differential counting of white blood cells among the treatments (P<0.05), but there was no significant difference in the amount of WBC among the treatments (P>0.05). After 10 weeks, there were significant differences in the amounts of Monocytes, Lymphocytes and Eosinophils (P<0.05), but there was no significant differences in the amount of other hematologic factors (P>0.05). At the end of the experiment (15th week) only WBC, RBC, Monocyte, lymphocyte and neutrophil showed significant differences between the treatments (P<0.05) and other hematologic factors did not show any significant differences between the treatments (P>0.05). The results of biochemical indices analysis showed significant differences (P<0.05) among treatments for all of the parameters for 5th weeks, total protein and glucose for 10th week and only cholesterol for 15th week. The carcass analysis at the end of experiment showed that only the amount of carbohydrate, protein and ash were significantly difference between the treatments (P<0.05). The results of growth parameters at the end of 3th, 9th, 12th and 15th week showed significant differences between the treatments (P<0.05), but at the end of 6th week only GR was significantly different between the treatments (P<0.05). After concerning acute stress test including reduce water volume, cutting the aeration for 30 minutes at the end of experiment, cortisol and glucose significantly increased (P<0.05) compared with prestress period, but the lowest response to the stressor was observed in fish fed by E400 C 400 mg/kg. On the other hand the survival was 100% during the experiment and no mortality was occurred during this period. Results of this study indicate that Vitamins C and E can have remarkable effects on hematological, biochemical and growth indices in different growth periods. So regarding the effects of vitamin C and E on some growth indices, it seems that the diet containing E400 C 100 mg/kg can be considered as the optimum diet in the rearing condition for this weigth range of fish.