WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 31 Aquaculture has grown consistently over the last decade, mainly in developing countries. Global aquaculture production will continue to grow, mainly as a result of improvements in production technology and increased demand for seafood. However, aquaculture faces several important challenges in terms of efficient use of raw materials, health management and environmental impact. Challenges in Aquafeeds Reliance on scarce and costly raw materials, such as fishmeal, and the optimal use of alternative ingredients constitute one of the main concerns in aquaculture. Consumer awareness about environmental sustainability also encourages producers to improve production performance through implementation of sustainable aquaculture practices. However, the use of less costly protein sources and low-nutrient dense diets most likely will lead to lower protein digestibility, greater amino acid imbalance and greater carbohydrate and fiber content. These can lead to inefficient nutrient use, resulting in increased feed usage and consequently greater production costs. In addition, sub-optimal animal performance leads to greater susceptibility to disease and greater ammonia emissions, which increases the ecological footprint. Phytogenic feed additives, consisting of herbs, spices, extracts or other plant-derived compounds, have gained considerable attention as one answer to these challenges. Active ingredients such as phenols and flavonoids can exert multiple effects in animals, including improvement of feed conversion ratio (FCR), digestibility, growth rate, reduction of nitrogen excretion and improvement of the gut microbiota and health status. Phytogenics and Feed Efficiency The replacement of fishmeal by plant protein, whether for economic or sustainability reasons, can decrease feed efficiency and suppress an aquatic animal’s immune system. Plant raw materials are less digestible and have a negative impact on the gastrointestinal tract. The presence of undigested nitrogenous compounds in the intestine favors the formation of ammonia and biogenic amines by intestinal microbiota. These toxic compounds cause an imbalance of intestinal microbiota, resulting in inflammation and accelerated turnover of intestinal tissue, leading to poor performance and disease vulnerability. Phytogenics stimulate digestive secretions, increase villi length and density and increase mucus production through an increase in the number of globlet cells. Through different strategies, phytogenics can improve feed digestibility, especially for proteins and amino acids, and increase disease resistance. These effects are illustrated in a trial made with gilthead seabream Sparus aurata at the University of Algarve, Portugal. In this trial, fish were fed a low fishmeal diet (14 percent) supplemented with a matrixencapsulated phytogenic feed additive (Digestarom®)1 to evaluate its efficacy on feed efficiency, body composition, pepsin activity and nutrient retention. Dietary supplementation with Digestarom® resulted in a significant reduction of FCR from 1.28 to 1.12 (Fig.1) and an improvement of weight gain and specific growth rates (from 1.76 to 1.82 percent/day). Inclusion of the phytogenic product in the diet significantly enhanced protein and fat retention (Fig. 2). There was a Four Ways Phytogenics Can Address Aquaculture Challenges Rui Gonçalves and Gonçalo Santos (CONTINUED ON PAGE 32) TOP, FIGURE 1. FCR of sea bream as affected by supplementation of diets with matrix-encapsulated phytogenics (Digestarom® P.E.P. MGE). Bars lacking a common superscript differ significantly (p<0.05). Source: Biomin trials (2012). MIDDLE, FIGURE 2. Nutrient retention (protein and fat) of seabream as affected by supplementation of the matrixencapsulated phytogenics (Digestarom® P.E.P. MGE). Bars lacking a common superscript letter differ significantly (p<0.05). Source: Biomin trials (2012). BOTTOM, FIGURE 3. Nitrogen budget (gain, faecal losses and metabolic losses) in sea bream as affected by supplementation on matrix-encapsulated phytogenics (Digestarom® P.E.P. MGE). Bars lacking a common superscript letter differ significantly (p<0.05). Source: Biomin trials (2012).
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