Role of Bifidobacterium bifidum for Enhancing Growth and Disease Resistance in Tilapia against Aeromonas hydrophila Challenge

Probiotics have been employed to improve the growth enactment and enhance immune responses in animals. We have assessed the effectiveness of Bifidobacterium bifidum (B. bifidum) as probiotic supplementation on growth, serum hormones, body composition, respiratory burst and lysosome activity in Aeromonas hydrophila (A. hydrophila) challenged Nile tilapia. For growth analysis fingerlings were divided into five groups viz. control: untreated, B1, B2, B3 and B4 (2, 4, 6 and 8 g of probiotic per kg of fish feed, respectively). Growth was monitored fortnightly and at the end of the experimental period of three months. Significant variations in growth, serum hormones (growth and thyroid) and body composition (protein, carbohydrates, fatty acids, and amino acids) were noted in fingerlings fed with B. bifidum. An in vivo challenge assay with A. hydrophila was performed in which the optimum concentration of the probiotic devised from the growth assay (4 g/kg feed) was delivered to the challenged fingerlings. Fingerlings were divided into four groups in the challenge assay viz. control (control negative), B. bifidum, A. hydrophila (positive control) and A. hydrophila + B. bifidum-treated. Distinct differences were recorded in hematological parameters between the challenged and B. bifidum-treated challenged groups. Respiratory burst and lysosome activity were also improved in challenged group treated with B. bifidum. Histopathological changes were observed in A. hydrophila challenged fingerlings, while the A. hydrophila + B. bifidum-treated group exhibited fewer deformations showing the affirmative effect of the probiotic supplementation. Our results manifest the benefits of incorporating B. bifidum as a feed increment to increase growth and the health status of Nile tilapia.