Effects of different stocking densities on haematological, non-specific immune, and antioxidant defence parameters of striped catfish (Pangasianodon hypophthalmus) fingerlings reared in finger millet-based biofloc system

Abstract

A study was conducted to investigate the effects of different stocking densities on growth, haematological, non-specific immune, and antioxidant defence parameters of striped catfish (Pangasianodon hypophthalmus) fingerlings reared in a finger millet-based biofloc system. Striped catfish fingerlings with a mean initial weight of 7.34 ± 0.06 g were randomly stocked in triplicate at six different treatment groups, which included 150/m3 (T1), 180/m3 (T2), 210/m3 (T3), 240/m3 (T4), and 270/m3 (T5) in biofloc-based units, and 150/m3 (C) with clear water in plastic crates (capacity 160 L) and reared for 90 days. Finger millet flour was used as an organic carbon source with a 15:1 C:N ratio. After 90 days of rearing, significantly (p < 0.05) higher, percentage weight gain (298.21 ± 9.92%) and daily growth index (0.24 ± 0.01) were obtained in T1 (150/m3) and lower values were recorded in T5 (270/m3). The antioxidant defence response, SOD, and CAT activity of liver and gill tissues were significantly (p < 0.05) lower in the T5 (270/m3) experimental unit and higher in the T1 (150/m3) experimental unit. Blood indices, haemoglobin, total erythrocyte, leucocyte count, packed cell volume, and mean corpuscular volume improved significantly (p < 0.05) in BFT units with stocking densities (150, 180, and 210/m3) compared to other experimental units. Stress enzyme responses, serum glucose (74.88 ± 4.48 and 77.15 ± 4.67 mg/dl), and serum cortisol (59.64 ± 4.62 and 60.65 ± 3.11 ng/ml) values were significantly (p < 0.05) reduced in BFT units (150, 180/m3) when compared to other experimental units. Non-specific immunity responses such as nitro blue tetrazolium activity (0.41 ± 0.02 OD at 540 nm), serum myeloperoxidase (1.08 ± 0.05 OD at 450 nm), and serum lysozyme activity (51.40 ± 2.02 U/ml) were significantly (p < 0.05) reduced in T5 (270/m3). From the results of the present study, it may be concluded that a stocking density of 240/m3 (T4) is ideal for overall individual growth, better immune, and stress responses of striped catfish culture in BFT system.