The dietary effects of two strain probiotics (Leuconostoc mesenteroides, Lactococcus lactis) on growth performance, immune response and gut microbiota in Nile tilapia (Oreochromis niloticus).

The aquaculture industry has been growing rapidly over the past few decades to meet future animal protein demands. However, intensive aquaculture industry faces challenges such as growth abnormalities, high mortality rates, water quality and intestinal health deterioration. Administering probiotics can serve as a nutritional strategy to enhance the immune system and growth performance of fish influxes of gut microbiota. This study aimed to evaluate the impact of two dietary probiotic strains L. mesenteroides and L. lactis on the growth performance, immunity, and gut microbiota of Nile tilapia (Oreochromis niloticus). Fish were fed with basal and experimental diet supplemented by both L. mesenteroides and L. lactis bacteria at 106 cell/g for 8 weeks. Feeding a combination of L. mesenteroides and L. lactis resulted in significant improvements in feed utilization parameters (PER and FER) (P < 0.001), alternative complement pathway activity, intestinal lactic acid bacteria count (P < 0.012), mucus secretion (P < 0.002) and peroxidase activity (P < 0.001) compared to the control groups. Serum lysozyme activity also exhibited a significant increase in the L. mesenteroides and L. lactis dietary group (P < 0.011) compared to the control and single probiotic supplemented diet groups. Furthermore, Nile tilapia fed the L. mesenteroides and L. lactis supplemented diet showed enhanced growth performance metrics (weight gain, final weight and specific growth rate) compared to those fed control and single probiotic supplemented diets (P < 0.022). Additionally, superoxide dismutase activity was significantly elevated in the L.mesenteroides and L. lactis supplemented diet groups compared to the control and single L.mesenteroides supplemented diet groups (P < 0.017). These findings strongly indicate that a dietary combination of L. mesenteroides and L. lactis probiotics could function as a beneficial immunostimulant feed supplement in Nile tilapia aquaculture.