Evaluation of Antarctic krill ( Euphausia superba ) meal supplementation in diets for olive flounder ( Paralichthys olivaceus )

Abstract

The supplemental effect of Antarctic krill meal (KM) into a low fish meal (FM) diet was evaluated for olive flounder (Paralichthys olivaceus). A 56% FM-based diet was regarded as a high FM inclusion diet (HFM), and a low-FM diet (LFM) was prepared by replacing 50% FM from the HFM. Four other diets were prepared by supplementing 3%, 6%, 9% and 12% KM into the LFM diet gradually replacing soy protein concentrate and tankage meal (designated as KM3, KM6, KM9 and KM12 respectively). Quadruplicate groups of fish were fed one of the diets for 12 weeks. The growth performance and feed utilization efficiency were improved by the dietary KM supplementation. Digestibility of dietary protein and dry matter was increased by the KM3-9 diets. Haematocrit and haemoglobin were increased by KM supplementation. The innate immunity and antioxidant capacity assessed by Ig, antiprotease, lysozyme, GPx and SOD and the condition factor of fish were significantly increased by KM3-9 diets. Moreover, goblet cell counts, villi length and fillet yield of fish were significantly improved by all the KM-containing diets (KM3-12). A 25-day-long challenge test with the Edwardsiella tarda pathogen showed that the cumulative mortality was higher in fish fed the LFM diet than in fish fed the HFM or KM-supplemented diets. The results indicate that dietary KM supplementation in a LFM diet can increase growth performance and feed utilization efficiency, diet digestibility, intestinal development and functions, innate immunity and disease resistance of olive flounder. The recommended level of KM inclusion in a LFM diet seems to be 6.6% according to quadratic regression analysis.