Growth Performance, Immune Modulation, and Gene Expression Enhancement in Labeo rohita Through Integrated Probiotic Bacillus licheniformis and Phytobiotic Cinnamomum verum Strategies

This study examines the dietary application of probiotic Bacillus licheniformis and phytobiotic Cinnamomum verum concerning growth, immunity, gene expression, and disease resistance in Labeo rohita fish. A controlled experiment was conducted over 12 weeks involving 800 fingerlings, which were divided into seven groups: one control group and three groups each receiving varying doses of B. licheniformis (D1 = 10⁵, D2 = 10⁷, and D3 = 10⁹ CFU/g) and C. verum (D4 = 25, D5 = 50, and D6 = 75 mg/kg) individually, along with a group with no additions (control). Growth was measured in terms of weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) alongside hematology and immunology. To evaluate resistance of the test organisms, pathogenic challenge with Aeromonas hydrophila was performed. The findings indicated that fish in the D3 group achieved the highest average final weight of 125.40 ± 0.1 g, a weight increment of 86.40 ± 0.53 g, and the most favorable FCR of 0.81 ± 0.01. The D6 group followed, in contrast to the control group, which had a body weight of 95.20 ± 0.2 g, a WG of 56.73 ± 0.05 g, and a FCR of 1.03 ± 0.06. The survival rates following the challenge were analyzed, revealing that group D3 exhibited the highest effectiveness (p < 0.001). The evaluation of immunological parameters in D3 indicated increased levels of total protein, immunoglobulin M (IgM), complement component 3 (C3), and lysozyme activity relative to D1 and D2. Analysis of gene expression revealed that interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) were upregulated in the liver and head kidney tissues of fish in the D3 and D6 groups. Bacillus licheniformis, when administered at 10⁹ CFU/g, enhances growth, feed utilization efficiency, immunity, and disease resistance in L. rohita. Cinnamomum verum at a dosage of 75 mg/kg improved the immune response. This study supports the consumption of probiotics and phytobiotics as substitutes for antibiotics in aquaculture.