Growth performance of pearlspot reared in insitu and ex situ biofloc system
The bio-growth parameters of pearlspot reared in
in situ and
ex situ biofloc systems are shown in Table 3. The results indicated that
in situ groups significantly (
P<0.05) performed well in terms of higher weight gain compared to
ex situ groups (
P<0.05). Improved weight gain was observed in the 20:1
in situ biofloc system due to the continuous availability of
in situ biofloc in the system. Similar results were documented by
Ezhilarasi et al., (2019) and
Elaiyaraja et al., (2020). Various studies resulted in
in situ biofloc performing higher growth in biofloc-raised tilapia
(Crab et al., 2009; Azim and Little 2008;
Elaiyaraja et al., 2020), L. rohita (Mahanand
et al., 2013;
Ahmad et al., 2016), Carassius auratus (Wang
et al., 2015),
Cyprinus carpio Najdegerami
et al., (2016) and
Etroplus suratensis Ruby et al., (2022) which indicates that biofloc can substitute aquatic animal feed and can promote the growth of diverse fish species.
The inclusion of biofloc as a dietary ingredient in the shrimp diet was found to improve the growth performance of
L. vannamei (Ju et al., 2008; Kuhn et al., 2010). Among
ex situ treatments, biofloc at 20% incorporation in the feed (EB-20) was recorded with higher weight gain. In contrast, shrimp fed higher biofloc incorporation in their diet had significantly lower growth performances which agrees with
Anand et al., (2014) who reported that an increase in biofloc meal dietary supplementation in the diet does not increase proportionately the digestive enzyme activities and thereby the growth of shrimp. Our study revealed that enhanced growth performances were obtained within the biofloc
in situ system compared to the
ex situ system.
Immune-physiological responses
Immune-Physiological responses in
E. suratensis reared with
in situ and
ex situ biofloc treatments are summarised in Table 4. The significant interaction (P<0.05) indicated that
in situ treatment enhances the overall immune-physiological function of pearlspot.
Increased Respiratory burst activity (RBA) was observed in IB-3 treatment (0.73±0.01) when compared to other
in situ and
ex situ groups. Significantly (
p<0.05) higher levels of Myeloperoxidase, lysozyme, Catalase and SOD were recorded in fishes reared in
in situ compared to
ex situ groups. In addition, decreased glucose (80.30±0.8) and cortisol (65.2±0.9) values were observed in the
in situ IB-3 treatment of
Etroplus suratensis when compared with
ex situ and other treatments. Respiratory burst activity is an indicator of oxygen-dependent bactericidal activities. The observed higher respiratory burst activity in the present study IB-3 was reported by
Ekasari et al., (2014) who found a higher respiratory burst activity in the post-challenge of shrimp reared under molasses-supplemented biofloc compared to rice bran and tapioca-by-product-supplemented biofloc systems.
Myeloperoxidase (MPO) is an important enzyme having antimicrobial activity. The present study recorded the highest MPO values in the IB-3 (7.5±0.08) groups, followed by IB-2, EB-2, IB-1 and EB-3 least value was documented in the EB-1 (4.17±0.30) group which similar to the inference of
(Long et al., 2015). The increased level of Lysozyme and catalase enzymes in the IB-3 and IB-2 agreed with the findings of
Anantharaja et al., (2023) in the
Hypselobarbus pulchellus. Superoxide dismutase (SOD) is a class of enzymes that catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. The SOD values obtained in the present study were in the range (50.86±0.4 to 33.59±1.3) reported in
Carassius auratus (Wang
et al., 2015). In the present study, there was a significant increase in SOD levels among
in situ biofloc-based treatments compared to
ex situ groups, which indicates the need for SOD activity to scavenge the oxidative radicals produced by higher respiratory activity among the
in situ biofloc treatments.
Serum cortisol is used as a general index for stress, which can be used to determine primary stress response in animals, including fish
(Metwally and Wafeek, 2014). In the current investigation,
ex situ treatments showed higher cortisol levels indicating more stress in this group. The results agreed with earlier findings in Nile tilapia
(Azim and Little, 2008). In the present study, a reduced trend of glucose content was observed in biofloc treated with probiotics, followed by biofloc and the serum glucose content was found highest in
ex situ which was highest among other treatments.
Whole body nutrient and amino acid composition
The whole-body crude lipid content were not significantly (p>0.05) affected by the
in situ and
ex situ groups (Table 5) However, higher crude protein content of the whole body was observed in fish reared in IB-3 followed by IB-2 and IB-1. Similar results were reported by
(Yuvarajan et al., 2023). There were significant (
p<0.05) differences observed in the whole-body essential amino acids’ profiles
viz., Phenylalanine, lysine, isoleucine, methionine and tryptophane when compared with
ex situ groups (Table 6). In the present study,
E. suratensis in
in situ biofloc showed a higher percentage of protein and lipid compared to
ex situ groups. The findings of the present study are in agreement with the results reported by,
Paul et al., (2024) in
Ompok pabda and
Hasbullah et al., (2018) in
Nile tilapia.
Muscle-related gene expression
The MyoD gene regulates muscle cell proliferation and differentiation during white skeletal muscle growth to create new hyperplastic fibres and hypertrophy
(McCarthy et al., 2011). The relative expression of muscle-growth-related genes in the white skeletal muscle of
Etroplus suratensis reared in
in situ and
ex situ biofloc with jaggery as a carbon source are illustrated in Fig 1A and B.
El-Hawarry et al., (2021) reported that adding glycerol as a carbon source at Low stoking density downregulated Growth gene expression without affecting MSTN expression. Further, he concluded that the upregulation of both IGF-1 and GHR1 genes 5 and 2.1-fold, respectively and growth-related genes upregulated in fish under LSD with glycerol and molasses as carbon sources. MSTN is a skeletal muscle mass-negative regulator gene that suppresses muscle growth
(Rodgers and Garikipati, 2008). To the best of our knowledge, there have been no previous investigations on the expression of muscle growth-related genes in
Etroplus suratensis grown in an
in situ and
ex situ biofloc farming system.
The pattern of the targeted muscle genes expression in pearlspot reared in (IB-3) 5.40-fold change revealed a clear pattern of statistically significant (
p<0.05) upregulation of Myo D. Similarly, in the
ex-situ groups, EB-2 expressed higher Myo D 4.33-fold than other treatments. The MyoD was upregulated in IB-3 and EB-2, respectively. On the contrary, the relative expression of
myostatin was downregulated in IB-3 0.99 and EB-2 1.28-fold changes. With an increase in the C: N ratio of carbon sources the relative muscle gene expression was upregulated.
However, these findings add to our understanding of the impact of
in situ and
ex situ biofloc technology in upregulating muscle growth gene expression which underlies the enhancement of fish growth. Future research should be done to investigate the role of
in situ and
ex situ biofloc in the expression and regulation of muscle growth-related genes.
