WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2016 57 Austria) in offsetting the negative effects of AFB1. Twenty four yellow catfish (2.02 ± 0.10 g/fish) were randomly distributed into 24 net cages (2 × 2 × 2 m). Fish were fed manually to apparent satiation one of eight experimental diets (Table 1) supplemented with concentrations of pure AFB1 ranging from 0 to 1000 μg/kg with or without the addition of Mycofix® Secure. After analyzing the experimental diets, AFB1 levels were greater than expected — aflatoxin levels exceeded the amount added to feed by researchers — probably a result of the natural aflatoxin contamination of ingredients used in the basal diets (12 and 27 µg/kg of AFB1 in diets). This fact highlights the risk of AFB1 contamination in feedstuffs used in aquafeeds. Weight gain was greatly affected by AFB1-contaminated diets (Fig. 1). Generally weight gain decreased with increasing dietary AFB1. The major impact was observed in catfish fed with 500 and 1000 µg/kg of AFB1. The negative response was considerably less pronounced when the contaminated feed was supplemented with Mycofix® Secure. When Mycofix® Secure was used in a diet with 1000 µg/kg AFB1, there was an improvement in weight gain of 9.64 percent. The major impact of aflatoxin was observed on feed conversion ratio, where dietary AFB1 at 500 µg/kg or greater led to a significant increase in FCR. A statistically significant interaction between binder and AFB1 in diet was also observed, representing a less accentuated increase in FCR when using the additive in the diet (Fig. 2). At a maximum level of AFB1 in the diet of 1000 µg/kg, FCR was 60 percent greater than the control. However, when Mycofix® Secure was used, FCR increased only by 24 percent. Thus, adding Mycofix® Secure resulted in an improvement of 36 percent of FCR. Survival decreased significantly with the increase of AFB1 in diets. At 1000 µg/kg of AFB1 in diets, survival was reduced by 22 percent compared to catfish in the control. With use of Mycofix® Secure, survival was reduced by just 13.5 percent (Fig. 3). Generally there was a negative effect on all immunity parameters analyzed throughout the treatments with the increase in AFB1 concentration. Groups supplemented with Mycofix® had less negative effects from AFB1 in comparison to catfish fed non-supplemented diets. Conclusion Yellow catfish appear to be sensitive to AFB1. A negative relationship between AFB1 level in the diet and fish survival, growth performance, feed efficiency and immunological parameters was observed. Diets containing 1000 µg/kg AFB1 were highly toxic to yellow catfish. The use of Mycofix® Secure decreased the negative impact of AFB1 toxicity on the fish. The results obtained represent an important step for counteracting AFB1 in aquaculture with significant potential for improved economic returns related to better FCR and survival. Notes Rui Gonçalves, Scientist – Aquaculture, BIOMIN Holding GmbH, Erber Campus 1, 3131 Getzersdorf, Austria, rui.goncalves@ biomin.net 1 Xinxia, Wang et al. In press. Responses of yellow catfish (Pelteobagrus fulvidraco) to different dietary concentrations of aflatoxin B1 (AFB1) and evaluation of an aflatoxin binder in offsetting its negative effects. Ciencias Marinas. FIGURE 2. Feed Conversion Ratio of yellow catfish at the end of the experiment. FIGURE 3. Survival of yellow catfish at the end of the experiment.
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