Abstract

Sustainable aquaculture, from both ecological and economic perspectives, demands a substantial reduction of the amount of fishmeal used in aqua feed. Instead, plant-derived protein feed stuff, which provide a nutritious diet offer a promising alternative for inclusion in aqua feed. In this study, the effects of organic selenium supplementation in low and high soybean meal-based practical diets for yellowtail kingfish (Seriola lalandi) were evaluated over a 60-day feeding experiment. The juvenile yellowtail kingfish (initial weight 5.02 ± 0.04 g fish −1 ) were fed five iso-nitrogenous and iso-caloric diets containing 49% crude protein and 22 MJ kg −1 gross energy. The control diet(C) includes 46% fishmeal, whereas the other diets used soybean meal to replace 25% and 75% of the fishmeal protein, both without and with organic selenium supplementation (SBM 25 , SBM 25+Se , SBM 75 , and SBM 75+Se ). Fish were fed ad libitum two times a day at 09:00 and 15:00 hours. No differences were observed in feed intake among dietary treatment groups (P > 0.05). Organic selenium-supplemented diets improved final weight; however, final weight was significantly reduced when fish were fed high soybean meal diets (P < 0.05). Organic selenium supplementation had a significant effect on specific growth rate at low soybean meal diets, but did not affect specific growth rate when fish were fed high soybean meal diets. Selenium accumulation in fish fillet was strongly correlated with selenium concentration in the diets. While fish fed the SBM 25+Se diets had significantly higher glutathione peroxidase activity than those fed other diets, the lowest glutathione peroxidase activity was found in fish fed SBM 75 diets. Histologically, selenium-deficient diets induced myopathy and alterations in tissue structure were most prevalent in fish fed the SBM 75 diet. The findings of this study indicate that, with Se supplementation, soybean meal could supply 25% of the protein in yellowtail kingfish diets.

Highlights

  • One of the major challenges facing the aquaculture sector worldwide is the limited utility of formulated feed containing fishmeal (FM) from wild sources

  • organic Se (OS) supplementation had no effect on SGR for low Soybean meal (SBM) diets, it did when fish were fed high SBM diets and the SGR of fish fed the SBM75+Se diet was significantly higher than that of fish fed the SBM25 diet

  • An improved FCR was observed in fish fed with OS-supplemented diets, no difference in SGR was found between the SBM75 and SBM75+Se dietary groups

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Summary

Introduction

One of the major challenges facing the aquaculture sector worldwide is the limited utility of formulated feed containing fishmeal (FM) from wild sources. Phytic acid is one of the most common ANFs in PP feed stuffs, since around 56 - 81% of total phosphorus (P) in SBM is stored asphyxiate[14]. This phytic acid-bound P cannot be hydrolysed by monogastric animals, including fish[15]. Phytate chelates divalent mineral cations such as Iron (Fe), Zinc (Zn), Magnesium (Mg), Manganese (Mn), Copper (Cu), Calcium (Ca) and Selenium (Se), limiting availability of P and other minerals in SBM-based diets[13,16]. Phytate may form insoluble complexes with protein and amino acid (AA) cations in PP feed stuffs, diminishing their digestibility for fish[17]. Supplementation of trace minerals has been applied to the diets of several fish species to improve mineral bioavailability[18,19,20]

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