| dc.description.abstract |
From the present study, it is clear that all the three metals,
selenium, molybdenum and cobalt have significant effect on the
antioxidant status of the shrimps. Selenium and molybdenum were
observed to induce peroxidative damage at elevated levels. But at the
same level, cobalt did not show such an effect.
Selenium was found to be growth promoting at lower levels of
dietary supplementation. Even though low levels of dietary selenium
had a protective effect against the lipid peroxidation, the present study
indicates that high levels of dietary selenium could promote lipid
peroxidation. The selenium-dependent antioxidant enzyme, GPx
behaved differently in muscle and hepatopancreas. A high
concentration of selenium was required for the active expression of
the enzyme in the muscle, where as in hepatopancreas maximum
activity was observed at lower selenium concentration. Selenium
supplementation had a positive effect on GSH concentration. The
other antioxidant enzymes such as GST, SOD and CAT showed
enhanced activity at higher concentration of selenium.
Molybdenum supplementation significantly reduced the free
radical scavenger enzymes SOD and CAT. This resulted in enhanced
lipid peroxidation in tissues. The activity of antioxidant enzyme GPx
and the concentration of the substrate for the enzyme, GSH also were lower at elevated levels of molybdenum supplementation. In addition
to this amino acids and fatty acids were also altered in molybdenum
supplemented groups. In trace amounts, dietary molybdenum exerts a
beneficial effect on the growth and also in the activities of the
enzymes XO and SO. At the same time it also indicates a possibility
of oxidative damage as a result of the peroxidation caused by the
activities of the enzymes SO and XO at elevated concentrations of
molybdenum is also indicated. The absorption of various trace
elements was also altered by molybdenum supplementation.Among the three metals studied, cobalt was the least toxic one
at the administered levels. But this metal has a significant effect on the
lipid content, amino acid composition, cholesterol levels and
phospholipid levels. Increased growth was also observed as a result of
cobalt supplementation in shrimps. The antioxidant system of the
animal was activated by dietary cobalt. Tissue levels of the trace
metals were also found to be altered in cobalt supplemented groups of
shrimps.These studies, thus shows that influence of dietary trace metals
calls for more detailed studies in farmed shrimp. They may hold the
key to growth and even disease resistance in shrimp. But this still
remains as a virgin field which demands more attention, especially in
view of the increasing importance of shrimp farming. |
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