author(s)
Ishfaq Nazir Mir, Sahu NP and Ngairangbam Sushila

abstract
Fucoidan was extracted productively from Sargassum wightii and its antioxidant potential was investigated. The isolated fucoidan content of 5.6% of dried seaweed powder was recorded. The in vitro antioxidant activity by 1, 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, total phenolic contents and reducing power assays of fucoidan rich extract (FRE) were evaluated. The extract showed enhanced antioxidant properties in a concentration dependent manner. Later, feeding trial of 60 days was conducted to observe any synergistic effect of methionine supplementation along with FRE on mitigation of stress due to Aeromonas hydrophila challenge, in which 420 Labeo rohita fingerlings were randomly distributed into seven groups in triplicates fed with different experimental diets by following a completely randomised design. There was no significant (P>0.05) effect on stress related enzymes like superoxide dismutase, catalase, aspartate transaminase and alanine transaminase before the bacterial challenge, indicating stress free condition. But, the activity of enzymes in the group containing 2% FRE along with low dose methionine was significantly reduced among all the treatments during the post A. hydrophila challenge period. These results proved that the stress resulted from the bacterial challenge was mitigated synergistically by 2% FRE along with low dose methionine in the diets of L. rohita fingerlings.