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Bài báo - Tạp chí
(2015) Trang: 45
Tạp chí: Aquatic products processing cleaner production chain for healthier food
Liên kết:

The aim of study is to find out the effects of nitrite on physiological responses and the growth of Chitala ornata (Gray, 1831), an air breathing fish had high nitrite tolerance with a LC50-96h of 360mg/L. The first experiment was carried out on the effects of nitrite on physiological parameters. The fish was 31.8 ± 1.8g of body weight and stocked in the tanks for 2 weeks, then exposed to nitrite  with density 100 fish/tank (200L) for each treatment; there were control and 2 treatments (46mg/L and 115mg/L). The blood samples were collected at 0, 1, 24, 48, 72, 96, 120, 144 and 168h after exposure for analysis the physiological parameters (ten fishes for each sampling time, n=10). The second experiment was to determine the growth of fish consisted of 4 treatments such as control, 10 mg/L, 18 mg/L and 180 mg/L at 30, 60 and 90 days. The fish was 11.53±0.15g of initial body weight, 3 replicates (3 tanks/ treatment) and 50 fish/ tank (500L). The result showed that plasma nitrite increased during experimental time; however, it maintained below exposed levels, plasma nitrate also soared by a number of mM, showing that a large proportion of nitrite absorbed was transformed to nitrate by denitrification processes. At the treatment 115 mg/L, metHb generated from the reaction between nitrite and erythrocyte haemoglobin (Hb) reached to 38% at 48h compared with 0.7% at 0h; HbNO boosted to 11% of total Hb at 96h compared with 0% at 0h; and functional Hb droped down 54% of total Hb at 48h compared with 99.3% at 0h. The ions balance was significantly influenced, typically plasma chloride decreased from 100 mM at 0h to 60 mM at 120h while plasma bicarbonate increased from 10 mM at 0h to 19mM at 168h. After rearing 90 days, daily weight gain (0.25±0.02g) and specific growth rate (1.18±0.07g) of the fish at the treatment 180mg/L were  significantly lower than those in other treatments. The survival rate (59%) was also very low compared to those in others. This study will be the background for further studies about chronic nitrite impacts to accumulation of its residual in fish body, which related to food safety in aquaculture.

 


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