Growth, non-specific immunity and disease resistance of Labeo rohita against Aeromonas hydrophila in biofloc systems using different carbon sources

• Biofloc technology using organic carbon sources to study growth and immunity of Labeo rohita under zerowater exchange.
• Tapioca biofloc system showed improved non-specific immune response and biochemical parameters.
• Higher resistance against Aeromonas hydrophila infection in terms of relative percentage survival was recorded in Tapioca biofloc.

A 60 day growth trial was carried out to evaluate biofloc based rearing system for Labeo rohita fingerlings. The C/N ratio of 15 was maintained in four biofloc treatments (T1, T2, T3 and T4) using indirect and long-lasting carbon sources (tapioca, wheat, corn and sugar bagasse) along with one control (C). Each group consisted of triplicate tanks and each tank was stocked with 50 fingerlings (4.80 g ± 0.12) of L. rohita. Fishes were challenged with A. hydrophila 60 days post rearing and relative percentage survival (RPS) was recorded over 14 days post challenge. Serum samples were collected on 20, 40 and 60 days interval of sampling for the evaluation of non-specific immune and stress parameters. The results revealed that fishes reared in tapioca based biofloc system showed significantly (p < 0.05) higher serum protein, serum albumin, total immunoglobulin, respiratory burst activity, myeloperoxidase activity and lower serum glucose and serum cortisol when compared to wheat, corn, sugar bagasse based biofloc system and control. Growth, feed conversion ratio (FCR), feed efficiency ratio (FER), and specific growth rate (SGR) of fishes in the biofloc treatments were significantly better (p < 0.05) than control. Tapioca based biofloc treatment showed significantly (p < 0.05) higher RPS (66.66%) than other treatments. The study suggests that the fishes reared using in-situ biofloc produced by tapioca can enhance growth and non-specific immune responses under zero water exchange system and hence ensures sustainability.Statement of relevance
• Zero water exchange reduces water scarcity and pollution problems
• Improves welfare of the animals by stimulating immunity and protection against diseases
• In-situ production of valuable microbial protein thus reducing dependence on fishmeal.