Supplementing with Dietary Lactobacillus acidophilus Modulates Cold Stress Deterioration of the Antioxidant Activity, Immunological Response, and Growth Indices in the Nile Tilapia

This study sought to show how feeding Lactobacillus acidophilus (LA) to the Nile tilapia (Oreochromis niloticus) might lessen cold stress (CS) deterioration of the antioxidant activity, immunological response, and growth performance. A preliminary trial was carried out dividing 180 fingerlings (28.6±0.24g) into 6 treatment groups according to the amount of LA supplied to the fish meals (0, 10², 10⁴, 10⁶, 10⁸, and 10¹⁰ CFU/g).  Each treatment group consisted of three replicate tanks, each containing 10 fish. To determine the appropriate lactic acid (LA) dosage and supplementation duration for the main study, preliminary testing was conducted. The results showed that supplementing fish feed with 10⁶ CFU/g of LA for four weeks was optimal for achieving significant growth improvements. In the primary experiment, 480 fingerlings (30.1±0.4g) were split up into two LA × two CS factorial treatment groups, each of which included six replicate tanks with 20 fish. During a 4-week feeding period, fish in LA groups were fed a baseline diet with 10⁶ CFU/g LA (+ LA group) or without LA (– LA group). Fish in each feeding group were further distributed into two subgroups either kept at 26°C (– CS subgroup) or subjected to cold stress at 18°C (+ CS subgroup). The findings demonstrated that, compared with the control fish, CS substantially (P< 0.05) reduced the antioxidant activity, immunological response, and growth indices in the challenged fish. Conversely, adding LA to fish feeds improved (P< 0.05) the antioxidant activity, immunological parameters, feed intake, and growth indices. In fish under cold stress, LA therapy reduced the increased mortality, heterophil to lymphocyte (H/L) ratio, and lipid peroxidation. In conclusion, LA feeding at 10⁶ CFU/g to the Nile tilapia fish might be suggested as a promising way to promote the fish's health and growth, particularly when they are subjected to CS circumstances.