No abstract

A 12‐wk feeding trial was conducted to evaluate the effects of the dietary fishmeal analogue (FMA) adding 2% shrimp soluble extract (SSE) on growing rainbow trout, Oncorhynchus mykiss. Fish averaging 146 ± 3.8 g (mean ± SD) were randomly distributed into 500‐L aquaria as groups of 20 fish per tank. Fish were fed the experimental diets in triplicate groups to apparent satiation twice a day on a dry matter basis. Each group was fed one of the four experimental diets: control (FM100% + FMA0%), FMA0 (FM100% + FMA0% + SSE2%), FMA12 (FM88% + FMA12% + SSE2%), and FMA24 (FM76% + FMA24% + SSE2%). After the feeding trial, weight gain and specific growth rate of fish fed the FMA0 and FMA12 diets were significantly higher than those of fish fed the FMA24 diet (P < 0.05). Feed efficiency and protein efficiency ratio values of fish fed the control, FMA0, and FMA12 diets were significantly higher than those of fish fed the FMA24 diet (P < 0.05). The values of superoxide dismutase activity showed significantly higher amounts for the FMA0, FMA12, and FMA24 groups than the control group (P < 0.05). Lysozyme activity in the FMA12 group was significantly higher than in the control group (P < 0.05). Therefore, according to our results, FMA with additive SSE can be used up to 12% as a substitute of fishmeal for growing rainbow trout.

The present experiment was conducted to evaluate the efficacy of dietary fermented by-product of mushroom, Pleurotus ostreatus, (FBPM) as a fish meal (FM) replacer in juvenile Amur catfish, Silurus asotus. A total number of 225 fish averaging 5.7±0.1 g (mean±standard deviation) were fed one of the five experimental diets formulated to replace FM with FBPM at 0%, 5%, 10%, 20%, and 30% (FBPM0, FBPM5, FBPM10, FBPM20, and FBPM30, respectively). At the end of eight weeks of the experiment, average weight gain (WG) of fish fed FBPM0 or FBPM5 were significantly higher than those of fish fed FBPM20 or FBPM30 diets (p<0.05). However, there was no significant differences in WG among the fish fed FBPM0, FBPM5 or FBPM10, and between fish fed FBPM10 or FBPM20, and also between those fed FBPM20 or FBPM30 diets. Lysozyme activity of fish fed FBPM0 or FBPM5 were significantly higher than those of fish fed FBPM10, FBPM20 or FBPM30 diets (p<0.05). The chemiluminescent response of fish fed FBPM5 was significantly higher than those of fish fed FBPM0, FBPM20 or FBPM30 diets (p<0.05). Broken line regression analysis of WG suggested that the maximal dietary inclusion level for FBPM as a FM replacer could be 6.3% without any adverse effects on whole body composition and on serological characteristics. Therefore, these results may indicate that the maximal dietary inclusion level of FBPM as a FM replacer could be 6.3% in juvenile Amur catfish.

The present study was conducted to evaluate the efficacy of organic acid blends as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus. Fish averaging 3.5 AE 0.05 g (mean AE SD) were fed one of the four experimental diets:(1) without antibiotic or organic acid (Control/CON); (2) with antibiotic-50 mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A-4 g/kg diet (OA A ); and (4) with organic acid blend B-4 g/kg diet (OA B ), for 10 weeks. At the end of the experiment, total intestinal bacterial counts in fish-fed OA A , OA B and OTC were significantly lower than that of fish-fed CON diet (p < 0.05). Further, the group of fish-fed organic acid blends (OA A , OA B ) or antibiotic (OTC)-supplemented diets exhibited lower intestinal Vibrio sp. counts compared with fish-fed CON diet. Disease challenge test with bacteria Edwardsiella tarda showed significantly lower cumulative mortality rates for the group of fish-fed OA A , OA B or OTC than that of fish-fed CON diet (p < 0.05). There were no negative effects on the growth, serological characteristics and proximate composition among the group of fish-fed different experimental diets. Therefore, the present experiment demonstrates that blends of organic acid could be a promising alternative to dietary antibiotics for the preventive and/or curative health management in marine fish olive flounder aquaculture. K E Y W O R D Santibiotic, blend, disease, organic acids, replacement

An 8-week feeding trial was conducted to evaluate the synergistic effects of dietary vitamin E and selenomethionine (SeMet) on induced methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. Nine semi-purified diets were formulated to contain three different vitamin E levels as DL-a-tocopheryl acetate (0, 100 and 200 mg TAkg À1 diet) and three different selenium (Se) levels (0, 2 and 4 SeMet mg kg À1 diet) on the constant mercury toxicity level (20 mg MeHgkg À1 diet). Nine experimental diets, 4 ), were fed to triplicate groups of fish averaging 2.3 AE 0.04 g (mean AE SD) in the semi-recirculation system. After 8 weeks of feeding trial, vitamin E and Se showed significant effects on weight gain (WG) of fish (P < 0.05). We found that there was a clear trend of increasing WG with elevating vitamin E and Se levels in the diets. Feed efficiency (FE), specific growth rate (SGR), protein efficiency ratio (PER) and survivability exhibited a similar trend with WG. Both antioxidants had significant interaction effects on FE and PER (P < 0.05). Methylmercury concentrations in fish muscle, liver and kidney decreases in a dose-dependent manner as dietary vitamin E and Se levels increase. Interestingly, the most significant interactive effects of vitamin E and Se were found in liver tissue for depleting Hg concentrations (P < 0.05). These findings suggest that dietary vitamin E more than 100 mg TA kg À1 diet with 2 or 4 mg SeMet kg À1 -supplemented diets could have synergistic effects on growth and liver mercury bioaccumulation on MeHg-induced toxicity in juvenile olive flounder.