The present study aimed to study the effectiveness of some over-wintering regimes (covering the tanks with polyethylene sheets, supplementation the fish diets with L-carnitine and using the bio-floc technology) on survival rate, growth performance and proximate composition of Nile tilapia (Oreochromis niloticus). The experiment was carried out during winter season (1st February to 1st April 2013) and the most important results can be summarize as follows:
At the experiment end (after 90 days), the three regimes, plastic sheet, L-carnitine and bio-floc technology, BFT significantly improved survival rate of O. niloticus and the most effective over-wintering regime (based on survival rate) was recorded by BFT followed by supplementation the diets with L-carnitine and by covering ponds with plastic sheets.
Fish in the BFT regime showed the highest body weight (BW), the longest body length (BL), the best weight gain (WG) and specific growth rate (SGR) and consumed the highest amount of feed and showed the best feed conversion ratio (FCR) and protein efficiency ratio (PER) compared to the other over-wintering regimes and control, and the differences between the other feeding regimes (L-carnitine, covering with plastic sheets and control groups) for feed intake, FCR and PER are not significant. Fish group of the bio-floc (BFT) gained the highest significant crude protein and ash and the lowest fat and dry matter content compared with control group.
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