Abstract

As capture fisheries are now fully exploited in Egypt, aquaculture is considered the only source for meeting the demand of seafood for rapidly growing populations in Egypt. To meet these demands for seafood, aquaculture has to grow fast and to be more intensive. Fishmeal sources from capture fisheries are fully exploited and thus become costly ingredient in fish and crustacean feed formulations. The present study evaluated biofloc technology as a sustainable alternative to fishmeal in the shrimp feeds using cheap carbon source for stimulation of the microbial biofloc growth, in addition to reduce protein content of the shrimp feeds. The shrimp were fed on three different diets (Control 45% CP, BF_25.10 and BF_30.10). The shrimp were cultured for 150 days. The water quality in biofloc-based pond was maintained with the promotion and development of biofloc through rice bran addition during the experiment. At the end of the experiment, the total yields of the shrimp in the two biofloc treatments were significantly higher than those of the shrimp in the control group (P < 0.05). The results indicated that promoting biofloc through carbohydrate addition in culture systems could enhance growth performance and water quality of cultured shrimp under the conditions of the present study. Feed conversion ratio (FCR) was significantly (P < 0.05) differed among treatments compared to control diet (1.51 ± 0.11; 1.66 ± 0.13 and 1.80 ± 0.10 for BF_25.10; BF_30.10 and control, respectively). There were significant differences (P < 0.05) in shrimp mean final weight between treatments and control diet (37.10 ± 2.22 g; 35.31 ± 1.52 g and 33.24 ± 2.17 g for BF_25.10; BF_30.10 and control, respectively). Mean survival (70 ± 8.30%; 66 ± 9.10% and 57 ± 11.00%, for BF_30.10 ; BF_25.10 and control, respectively. was significantly differed among treatments compared to control diet. The data suggests that substituting high-protein (Control 45% CP) with low-protein (BF_25.10 and BF_30.10) feed in a biofloc dominated system operated with minimal discharge may provide an alternative to improve shrimp farming technology, through improved water quality, cheaper (lower protein) feed and reduced environmental impact. The biochemical composition of the biofloc treatments did not vary significantly. Biofloc grown on BF_25.10 had higher protein content (23 ± 7 % DW) than BF_30.10 treatment (18 ± 5 %DW). The composition of the PUFAs in the biofloc showed that the treatment of biofloc with BF_25.10 contained significantly more total n-3 PUFA and total n-6 PUFA than that with treatment of BF_30.10. The results of the present study proofed that biofloc is a possible additional nutritious aquaculture feed for shrimp.

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