Effects of Indigenous Probiotic Bacterial Strains ( Rossellomorea marisflavi , Micrococcus luteus , and Paucilactobacillus vaccinostercus ) on Growth Performance, Survival, and Haematological Parameters of Nile Tilapia ( Oreochromis niloticus )
Abstract
Growing demand for sustainable aquaculture has intensified interest in non‐antibiotic strategies to enhance fish growth, health, and productivity. Host‐gut‐adapted indigenous probiotics have been proposed as promising alternatives to non‐native commercial strains, though their efficacy requires systematic evaluation. In this study, three indigenous strains— Rossellomorea marisflavi , Micrococcus luteus , and Paucilactobacillus vaccinostercus —were evaluated as dietary supplements for Oreochromis niloticus . A 12‐week feeding trial was conducted under a completely randomized design with four dietary treatments: basal control and three diets each supplemented with one probiotic at 1 × 10 8 CFU g − 1 feed, in triplicate. Fingerlings of initial mean weight 50.1 ± 0.06 g were fed to apparent satiation twice daily. Water quality parameters remained within acceptable ranges for O . niloticus and did not differ among treatments ( p > 0.05). Overall, growth performance and haematological indices were statistically comparable across diets ( p > 0.05 for all comparisons). However, the highest numerical values for final weight (137.4 ± 5.6 g), weight gain (87.3 ± 5.5 g), percentage weight gain (174.2 ± 10.3%), specific growth rate (1.20 ± 0.04% day − 1 ), and lowest feed conversion ratio (1.44 ± 0.05) were consistently recorded in P . vaccinostercus ‐fed fish. Survival was high across treatments (95%–99%), with the maximum value observed in the P . vaccinostercus group. Haemoglobin, packed cell volume, and total white blood cell counts were marginally higher in P . vaccinostercus ‐fed fish, whereas R . marisflavi and M . luteus performed similarly to control. No statistically significant improvements in growth, survival, or haematology were detected, and no adverse effects were observed under experimental conditions. These numerical trends for P . vaccinostercus should be interpreted as preliminary tendencies rather than conclusive probiotic efficacy. The findings provide basis for further evaluation of the three host‐derived isolates as a multi‐strain consortium to determine whether synergistic interactions can enhance growth, immune modulation, and disease resistance in tilapia aquaculture.