The nutrient profile of biofloc
Proximate and fatty acid profile results of biofloc have been given in Table 1. In the present study, dried biomass of biofloc contained low crude protein (16.61±0.02%) due to the major influence of diet (17% crude protein) and DSW as carbon source (Da Silva et al., 2018).
This result was falling with the report of Da Silva et al., (2018)
who analyzed biofloc crude protein ranged from 15.09 to 20.31%. On the other hand, GIFT fry growth performance was enhanced in outdoor lined pond biofloc system, which is indicated by significantly (P<0.05) better average body weight, food conversion ratio, protein efficiency ratio and 37% more total weight gain compared to control system (Yuvarajan et al., 2018).
These results were coherent with the findings of Luo et al., (2014)
and Long et al., (2015)
in indoor biofloc system based GIFT culture. The availability of balanced protein diet (biofloc) and stress free environment (lower nitrite and ammonia) may be the major reason for the growth performance of GIFT compared to a high CP supplementary diet in the biofloc system. According to Hisano et al., (2020),
tilapia have been feeding with 36, 32 and 36% of CP diet in nursery BFT (sugar cane molasses used as carbon source) and no significant difference was observed in terms of growth performance among treatments, but, the author suggested that 28% of CP reduced the feed cost and environmental impact. Floc encompassed low crude lipid and high crude fibre. The fibre content may condense the lipid level, the low level of lipid results was similarly reported by Long et al., (2015)
in GIFT tilapia culture and higher fibre content might influence the other nutrients of floc, similar findings were obtained by Mahanand et al., (2013)
in the biofloc based rohu culture pond. Total ash content found to be higher in dried biofloc, this result was parallel with Soares et al., (2004)
report (22-46%) in biofloc system. Out of twelve fatty acids (FAs), palmitic acid (16:0), palmitoleic acid (16:1n-7), oleic acid (18:1) and linoleic acid (18:2n-6) were dominated in biofloc system which is due to the viability of distillery spent wash as carbon source and dominance of heterotrophic bacteria and zooplankton, these results agreed with the findings of Crab et al., (2010).
Total n-3 (linolenic acid, ecosapentaenoic acid, docosahexaenoic acid) FAs found to be lower which is mainly due to the lack of microalgal communities and substantial increment of heterotrophic bacteria, the results were consonance with Anand et al., (2014)
results in biofloc system and also Aderme vega et al., (2012)
found microalgae played a significant role in omega-3 fatty acid production.
The nutrient profile of GIFT tilapia (whole-body)
Table 1: Proximate composition and fatty acid profile of dried biofloc.
Proximate and fatty acid profile results of biofloc have been given in Table 2. No significant difference (P>0.05) was observed in whole-body proximate composition except ether extract whilst slightly higher crude protein found in biofloc compared to control fish which is due to the positive influence floc protein consumption by the fishes. This result was in agreement with Azim and little (2008)
analyzed the nutrient profile in Nile tilapia from an indoor biofloc system. The ether extract was significantly (P<0.01) lower in biofloc fed fish than control fish which is due to the availability of live food and probiotic bacteria which have been balanced the lipid content of the supplemental diet. Azim and Little (2008)
found similar finding in biofloc based tilapia culture. No significant difference (P>0.05) was observed between the crude fibre of biofloc and control. But crude fibre was slightly higher in biofloc fish rather than control fish which is due to the ingestion of biofloc (16.03 ± 0.11% of CF). A similar result was reported in biofloc based culture of Penaeus vannamei
by Panigrahi et al., (2017).
Ash content was increased in biofloc fed fish than control fish, no significant difference (P>0.05) was observed between them. Similar report has been given by Verma et al., (2016)
in rohu fish body from biofloc system (sugar bagasse as carbon source). Out of twelve fatty acids, lower values of stearic acid (18:0), behenic acid (22:0) and docosahexaenoic acid (22:6n-3) have been found in biofloc fed fish body compared to control fish which is due to the lack of phytoplankton and dominance of heterotrophs in the culture water. Similarly, Aderme vega et al., (2012)
reported the importance of the microalgal role in the production of omega-3 fatty acids. Current study found significantly (P<0.05) rich fatty acids (myristic acid, arachidic acid and ecosapentaenoic acid) in biofloc than control fish which is due to FAs of biofloc positively influenced the FAs of the fish body through probiotic effect. Similar result was obtained in rohu when the probiotics supplemented with diet (Sinha and Pandey, 2013; Das et al., 2021).
Table 2: Proximate composition and fatty acid profile of dried whole fish body acquired from control and biofloc system.