The objective of this study was to conduct field experiments comparing formulated (extruded pellets (E.P)) and raw-fish (moist pellets (M.P)) feeds at two flounder aquaculture farms for six months to obtain the basic data necessary for improving aquafarmers’ awareness of feed-quality issues and firmly establish and expand the use of formulated feed. According to the results, the M.P group was higher in weight gain, feed efficiency ratio, protein efficiency ratio, and specific growth rate and lower in mortality rate than the E.P group. All cases of mortality were caused by six kinds of disease, four of which (Vibrio sp., Edwardsiella sp., Streptococcus sp., and Scuticociliates) were common to the two groups, whereas Lymphocystis arose only in the M.P group and abdominal inflation only in the E.P group at both farms. As for mortality in the present experiment, the numbers were 1047 at Da-Hae farm and 1167 at Global farm, with more fish dying in the E.P tanks than in the M.P tanks. By multiplying the number of deaths by selling price, the economic losses were $9650 and $10,756, respectively. Therefore, it should be considered an urgent priority to develop flounder-exclusive formulated feed for improved digestion and absorption rate and also to establish a water-quality-improvement management plan.

In this study, two bacterial species, Salipiger thiooxidans and Exiguobacterium aestuarii, were extracted and screened from the Saemangeum Reservoir. This study examined these species’ suitability as a probiotic by confirming the effects of S. thiooxidans and E. aestuarii added to rearing water for L. vannamei. Three experimental groups were evaluated for 6 weeks: (1) a control group reared in natural (i.e., untreated) water (CON), (2) an experimental group in which S. thiooxidans was added to natural water (SMG-A), and (3) natural water inoculated with E. aestuarii (SMG-B). The SMG-B group inoculated with E. aestuarii showed significantly higher final body weight, weight gain, specific growth rates, and feed efficiency than the control group. The SMG-B group inoculated with E. aestuarii exhibited significantly higher levels of serum lysozyme, and ACP and ALP activity than the control and SMG-A groups. The SMG-A and SMG-B groups inoculated with probiotics showed significantly lower total ammonia nitrogen and nitrite than the control group. Our findings suggest that S. thiooxidans and E. aestuarii extracted from the Saemangeum Reservoir can improve the water quality of aquaculture water, and, in particular, E. aestuarii is a potential probiotic for L. vannamei.

This study evaluated the effects of dietary supplementation with three silicate minerals (bentonite, zeolite, and illite) on the growth performance, whole-body composition, hematological and immune parameters, and apparent digestibility of Pacific white shrimp (Litopenaeus vannamei). Four isonitrogenous (35% crude protein) and isoenergetic (17.0 MJ kg⁻¹) diets were formulated: a control (CON) and three experimental diets containing 5% bentonite (BE), zeolite (ZE), or illite (IL), in which an equivalent amount of starch was replaced. Juvenile shrimp specimens (initial weight: 0.02 g) were reared for nine weeks and assessed for growth performance, feed efficiency, survival, biochemical indices, immune responses, and apparent digestibility. Shrimp specimens fed the illite-supplemented diet exhibited significantly higher final body weight (5.95 ± 0.97 g), weight gain, specific growth rate, and protein efficiency ratio than the other groups (p < 0.05). The feed conversion ratios were significantly better in the IL (1.10 ± 0.03) and ZE (1.16 ± 0.02) groups than that in the BE (1.26 ± 0.05) and CON (1.32 ± 0.04) groups (p < 0.05). The whole-body crude protein content was significantly higher in the ZE and IL groups. Hemolymph glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvate transaminase (GPT) activities were significantly reduced in the ZE and IL groups, indicating improved hepatic health. Non-specific immune responses, including nitro blue tetrazolium (NBT), phenoloxidase (PO), glutathione peroxidase (GPx), and lysozyme activities, were most enhanced in shrimp fed the IL diet. Apparent crude protein digestibility peaked in the IL group (93.3 ± 0.70%) followed sequentially by the CON (87.3 ± 0.92%), BE (87.8 ± 0.88%), and ZE (89.1 ± 1.11%) groups (p < 0.05). These findings demonstrate that dietary supplementation with illite significantly improves the growth performance, feed efficiency, hepatic condition, innate immune response, and protein digestibility of L. vannamei. Illite appears to be a promising candidate for functional feed supplementation aimed at enhancing productivity and health in intensive shrimp aquaculture.

This study evaluated how dietary supplementation with Haematococcus pluvialis powder (HPP), Arthrobacter bussei powder (ABP), and A. bussei probiotics affects growth, whole-body composition, non-specific immunity, antioxidant capacity, and nutrient digestibility in Pacific white shrimp (Litopenaeus vannamei). Juvenile shrimps were fed for 8 weeks with five diets: a control diet (CON), H. pluvialis powder (HPP, 1%), A. bussei powder (ABP, 1%), or A. bussei probiotics at 10⁵ (ABL) or 10⁸ (ABH) CFU g⁻¹ feed. Shrimp fed the ABP diet exhibited the highest final body weight, weight gain, and protein efficiency ratio, with a significantly improved feed conversion ratio than that of CON, ABL, and ABH groups. The HPP group exhibited significantly better growth than that of the control. Regarding immunity and antioxidant responses, lysozyme and phenoloxidase specific activities, as well as glutathione peroxidase and superoxide dismutase specific activities, were significantly enhanced in shrimp fed ABP and HPP diets, whereas malondialdehyde levels were significantly reduced compared with those in CON. Apparent crude protein digestibility was significantly higher in all supplemented diets than those in the CON group, with ABP showing the highest value. ABP and HPP supplementation improved growth, protein digestibility, and immune-antioxidant responses in L. vannamei, whereas probiotic forms showed limited effects. ABP is a superior functional feed additive than its probiotic form for enhancing productivity and health in shrimp aquaculture.