FEATURE
Controlling mycotoxins with binders by Adrien Louyer, aquaculture supervisor, Olmix Asia Pacific, Marie Gallissot, technical supervisor, Olmix SA, Dr Nguyen Van Nguyen, director of The Research Center for Fish Nutrition and Fishery Postharvest Technology - RIA2.
F
eed ingredients and feed prices are increasing; it is becoming harder to maintain the nutritional balance of the feed without increasing too much the feed price. Now, the use of ingredients from less stringent quality is likely to increase. Though plant materials are usually more reasonable in price than animal products, they can present problems through the presence of naturally occurring contaminants. Indeed, contamination of feed commodities by microorganisms and mycotoxins is the first negative factor impacting animal feed quality. Numerous researches have studied the decrease of performances with contaminated feeds. Lipopolysaccharides (LPS), also known as endotoxins, are present in the cell membrane of Gram negative bacteria. They are a structural component of the cell wall and are continuously released in the environment at cell death and during cell growth or division. Therefore, endotoxins are omnipresent in feed, water and fish gut which has shown to be an important bacterial reservoir. Endotoxins act as neurotoxic compounds and have immunosuppressive effect on fish. Mycotoxins are a diverse group of potential toxic metabolites produced by a variety of fungal species that often contaminate feedstuffs and consequently fish diets. Mycotoxins can vary in shape and size. They are heat stable and resist to extrusion process. For the ones that have been identified, it is known that a few parts per billion (ppb) already impact animal growth performances. Mycotoxins effects are specie dependent; cross contamination of different mycotoxins increases the damage caused (synergy) and
Table 1: Formulated diets with different MT.X+ doses (values are expressed as a % on an as fed basis) Feed Ingredients
D0 (0% MT.X+)
D0.05 (0.05% MT.X+)
D0.15 (0.15% MT.X+)
Fish meal 65%
17.00
17.00
17.00
Soybean meal
28.00
28.00
28.00
Cassava meal
18.75
18.75
18.75
Rice bran
35.00
35.00
35.00
0.3
0.25
0.15
Premix- M-V
0.30
0.30
0.30
Fish oil
0.50
0.50
0.50
Lysine (Lys)
0.10
0.10
0.10
Methionine (Met)
0.05
0.05
0.05
MT.X+
0.00
0.050
0.15
Total
100.00
100.00
100.00
Dry matter
89.22
89.22
89.22
Moisture
10.78
10.78
10.78
Crude protein
28.55
28.55
28.55
Crude fat
5.48
5.48
5.48
Crude fibre
5.86
5.86
5.86
Crude ash
8.84
8.84
8.84
Nitrogen free extract
40.34
40.34
40.34
Gross energy (kcal.g-1)
3.63
3.63
3.63
DCP
Proximate composition (% as fed basis)
Fishmeal 65 percent (Vietnam, Kien Giang); Soybean meal 47 percent (India); Fish Oil (Chile fish oil), cassava meal (Vietnam, Tay Ninh), Rice bran (Vietnam, Tien Giang), Lysine and Methionine (Japan)
results in uncharacteristic symptoms, thus making it difficult to diagnose mycotoxicosis. Even if extensive studies are done in this field, many mycotoxins effects remain unknown.
Prevention Because of their effect on the immune 16 | International AquaFeed | March-April 2013
system and fish performances, the presence of toxins impairs the farm economic performances. Strategies of prevention and control exist. In order to avoid deleterious effects of mycotoxins on fish, the best is to avoid contamination of the plants with molds through