An eight-week feeding trial was conducted to evaluate the effects of different dietary probiotic supplements in juvenile whiteleg shrimp, Litopenaeus vannamei. A basal control diet without probiotics (CON), and five other diets by supplementing Bacillus subtilis at 10⁷ CFU/g diet (BS₇), B. subtilis (BS₈), Pediococcus pentosaceus (PP₈), and Lactococcus lactis (LL₈) at 10⁸ CFU/g diet, and oxytetracycline (OTC) at 4 g/kg diet were used. Whiteleg shrimp with initial body weights of 1.41 ± 0.05 g (mean ± SD) were fed with these diets. Growth of shrimp fed BS₈ and LL₈ diets was significantly higher than those of shrimp fed the CON diet (p < 0.05). Superoxide dismutase activity in shrimp fed PP₈ and LL₈ diets was significantly higher than that of shrimp fed the CON diet (p < 0.05). Lysozyme activity of shrimp fed probiotics and OTC diets significantly improved compared to those on the CON diet (p < 0.05). The intestinal histology showed healthier guts for shrimp fed the probiotic diets (p < 0.05). Immune-related gene expression in shrimp fed BS₈, PP₈ and LL₈ diets was recorded as significantly higher than that of shrimp fed CON and OTC diets (p < 0.05). Also, results of the challenge test for 7 days and the digestive enzyme activity of shrimp fed BS₈, PP₈, and LL₈ were significantly improved compared to those on the CON diet (p < 0.05). Therefore, these results indicated that L. lactis at 10⁸ CFU/g could be an ideal probiotic for whiteleg shrimp, and also B. subtilis WB60 and P. pentosaceus at 10⁸ CFU/g could improve the growth, immunity, histology, gene expression, digestive enzyme activity, and disease resistance, while replacing antibiotics.

An eight-week feeding trial was conducted to evaluate the effects of a basal control diet (CON), Bacillus subtilis at 10⁷ (BS₇) and at 10⁸ CFU/g diet (BS₈), Lactococcus lactis at 10⁷ CFU/g (LL₇) and at 10⁸ CFU/g diet (LL₈), and oxytetracycline (OTC) at 4 g/kg diet on Nile tilapia. Fish with initial body weight of 2.83 ± 0.05 g (mean ± SD) were fed two times a day. Weight gain, specific growth rate, feed efficiency, protein efficiency ratio and lysozyme activity of fish fed BS₈, LL₈ and LL₇ diets were significantly higher than those of fish fed CON diet (p < 0.05). Superoxide dismutase and myeloperoxidase activity of fish fed BS₈, LL_8, BS₇, LL₇ and OTC diets were significantly higher than those of fish fed CON diet. Intestinal villi length and muscular layer thickness of fish fed BS₈, LL₈ and LL₇ diets were significantly higher than those of fish fed CON and OTC diets. Also, heat shock protein 70 (HSP70), interleukin (IL-1β), interferon-gamma (IFN-γ) and tumour necrosis factor (TNF-α) gene expression of fish fed BS₈ and LL₈ diets were significantly higher than those of fish fed CON diet. After 13 days of challenge test, cumulative survival rate of fish fed BS₈ and LL₈ diets were significantly higher than those of fish fed CON, BS₇ and OTC diets. Based on these results, B. subtilis and L. lactis at 10⁸ (CFU/g) could replace antibiotics, and have beneficial effects on growth, immunity, histology, gene expression, and disease resistance in Nile tilapia.

Olive flounder (Paralichthys olivaceus) also referred to as bastard halibut is a marine carnivorous species with great commercial value. The production of olive flounder has been dominated by aquaculture with 43 thousand tons of production in 2017 compared to fisheries with only 10 thousand tons in the same year. But despite the high market demand for this species, aquaculture production has not increased accordingly within the last decade. The development of olive flounder aquaculture has been facing several drawbacks such as improper feed formulations, dependence on unreliable ingredients (e.g. fish meal and fish oil), disease outbreaks, and excessive use of harmful antibiotics. All these factors are major impediments in the sustainable development of olive flounder aquaculture. A great body of research has been conducted to understand the nutrient requirements of olive flounder while finding alternative protein sources in the diet. Also, several feed additives have been successfully tested as immunostimulants in olive flounder. All these findings are thoroughly discussed in this review, therefore, the information can be utilized by the industry and academic societies.