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Effects of food availability on growth performance and immune-related gene expression of juvenile olive flounder (Paralichthys olivaceus)
- Lee, Seunghyung, Lee, Young Mee, Kim, Kyung-Hee, Kim, Hyun Chul, Park, Choul-Ji, Park, Jong-Won, Noh, Gyeong Eon, Kim, Woo-Jin, Hwang, Hyung-Kyu
- Fish & shellfish immunology 2018 v.80 pp. 348-356
- Paralichthys olivaceus, Toll-like receptor 3, aquaculture, body weight, energy content, environmental factors, farmed fish, flounder, food availability, gene expression regulation, genes, growth performance, immune response, immunoglobulin M, interleukin-8, juveniles, lysozyme, models, nutritional status, overfeeding, rearing, regression analysis, restricted feeding, shellfish, superoxide dismutase, tanks, weight gain
- Unfavorable environmental conditions and inappropriate culture practices have increased the vulnerability of cultured fish to disease infection. Up to date many studies have aimed to determine a feeding regimen to maximize productivity; however, very little information on immune responses of cultured fish in response to underfeeding or overfeeding is available. Therefore, a preliminary study was conducted to evaluate effects of graded feeding levels (i.e., food availability) on growth performance and immune-related gene expression of juvenile olive flounder (Paralichthys olivaceus). Six different feeding rates including 1, 4, 7, 10, 13, and 16% body weight per day (BW/d) were randomly assigned to three replicate tanks stocking 150 fish (average initial body weight: 0.27 ± 0.02 g; mean ± SD) per tank. A feeding trial lasted for two weeks. Based on the results of the weight gain, nutrient gain, and whole-body compositions and energy content, the feeding rate of 10%, 13%, and 16% BW/d resulted in high nutritional status, whereas the feeding rate of 1% and 4% BW/d resulted in low nutritional status. Intermediate nutritional status was observed at the feeding rate of 7% BW/d. In the given rearing conditions the optimum feeding rate resulting in the maximum growth was estimated to be 11.9% BW/d based on the quadratic broken-line regression model, chosen as the best-fit model among the tested models. Expression of immune-related genes including IL-8 and IgM was significantly down-regulated in the flounder fed at 1% BW/d in comparison to those fed at 7% BW/d. Interestingly, expression of these genes in the flounder fed at 10%, 13%, and 16% BW/d was relatively down-regulated in comparison to that of the flounder fed at 7% BW/d. Although no statistical difference was detected, overall response patterns of other immune-related genes, including TLR3, polymeric Ig receptor, lysozyme C-type, GPx, SOD, and Trx followed what IL-8 and IgM exhibited in response to the various feeding rates. Given the current challenges in aquaculture of the flounder our findings suggest to prohibit underfeeding or overfeeding (i.e., ad-libitum feeding) when culturing the young flounder.