Algae-clay powder (sea lettuce, Ulva lactuca and red algae, Solieria chordalis in exfoliated micronized montmorillonite) supplementation in a fish meal-reduced diet for olive flounder (Paralichthys olivaceus)

Abstract

Algae extracts or clay are supplement into animal feed to promote growth, digestive performance and health status. A feeding trial was conducted to evaluate supplemental effects of an Algae-clay powder (sea lettuce, Ulva lactuca and red algae, Solieria chordalis in exfoliated micronized montmorillonite, ACP) into a low fish meal (LFM) diet on growth and feed utilization, digestibility, innate immunity and disease resistance of juvenile olive flounder (26.5 ± 0.02 g). A high fish meal diet (HFM) was prepared to contain 55 % FM and the LFM was prepared to contain 44 % FM. The ACP was added into the LFM diet by 0.2 % (MF2). Negative effects of LFM diet were observed in growth, feed utilization and diet digestibility of fish after 12 weeks of the feeding trial. The ACP inclusion in the LFM diet had positive effects on all parameters showing similar or higher growth performance, feed utilization, digestibility, goblet cell counts and villi lengths than the HFM diet. Non-specific immune response and antioxidant parameters, such as lysozyme, total immunoglobulin, anti-proteases, superoxide dismutase and catalase were also significantly improved by the addition of ACP into the LFM diet. Activities of digestive enzymes were improved by ACP supplementation compared to LFM group. Following the feeding trial, a 21-day long challenge test against Edwardsiella tarda showed that MF2 group had higher cumulative survival compared to that of HFM or LMF group while a decreased survival was found in the LFM group. The findings in this study indicate that ACP supplementation in a LFM diet can improve growth performance, feed utilization efficiency, digestibility with digestive enzyme activities, intestinal development, innate immunity and disease resistance of olive flounder.