Mycotoxicoses can be due to toxic products contained in the raw material, or result from the alteration of the latter or one of its components. Micromycetes or molds develop from a nutrient substrate such as food or one of its initial components and produce toxins: mycotoxins.
Diseases caused by these mycotoxins are called Mycotoxicosis. Micromycetes are endowed with complete enzymatic equipment, especially of the Glycolytic (digestion of sugars) and Lipolytic (digestion of fats) types, which will allow them to degrade the substrate and thus reduce its overall food value (glycolysis, lipolysis, diversion of vitamins) . They will also have the effect of deteriorating the organoleptic qualities of food, leading to food rejection (musty taste).
Molds that potentially produce mycotoxins can develop on the plant in the fields (Fusarium), during the storage of the cereal before making the food, or on the food before consumption (Aspergillus and Penicillium). Mycotoxins may therefore accompany the raw material received by the feed manufacturer. Even if the stored cereal has undergone antifungal treatments before its reception, the molds are no longer present but the mycotoxins remain.
The food manufacturing process even with heat treatment will not destroy them since they are thermostable.
At the breeder, mold can also develop in the silo, especially if it undergoes significant temperature variations causing successive cycles of evaporation and condensation, and even more so if it is not weatherproof (the cap at the top is not watertight).
The housing under the auger is also an ideal place for mold growth, as food can settle there.
The food can also mold in the bottom of the plates if they are not emptied regularly.
In the case of a poorly insulated building, condensation can form on cold surfaces (ceiling, water pipes) and drip onto the plates.
The mycotoxins produced during storage are essentially aflatoxins (Aspergillus flavus) and ochratoxins, whereas those made in the field are trichothecenes, fumonisins or
azearalenone (Fusarium).
Ergotism
Rye is sometimes parasitized by micromycetes of the genus Claviceps which secrete mycotoxins (ergine, ergocristine, ergobasine). These act on the neuro vegetative synapses by causing vasoconstriction of the vessels, then necrosis of the extremities.
Aflatoxicosis
Aflatoxicosis is a condition caused by the ingestion of mycotoxins synthesized by the species Aspergillusjla – seen: as aflatoxins. These are mainly aflatoxins B and G. Among these, aflatoxin
Bi is ten times more toxic than aflatoxin Gi. Some strains produce aflatoxin Bi, other strains produce aflatoxin Gi. Aflatoxins are mainly found in groundnut seeds and their by-products (cake), as well as in poorly preserved cereals.
The development of the Aspergillus flavus type molds is favored by seed humidity above 15%, a temperature between 15 and 30°C, with an optimum temperature of 25°C, and a relative humidity of 80 or 85%. On the other hand, the toxins are elaborated if the temperature is lower than 10°C. This explains the high toxicity of specific maize dried in cribs in regions with highly variable climates at the end of winter.
Once produced, these aflatoxins are heat-stable: food cannot, therefore, be purified by heat.
Acute or chronic toxicity
In acute and subacute toxicity, hepatocyte damage ranges from overload to fatty degeneration.
If absorption of the toxic food ceases, scarring will result in cirrhosis (hepatic sclerosis and secondary ascites). Interstitial nephritis is also noted.
In the case of chronic intoxication, primitive “hepatomas” appear.
Symptoms according to species
At the duck
Acute aflatoxicosis is much more common in this species, which also serves as an experimental model for this type of poisoning (LD50 on day-old ducklings: 0.36mg/kg of aflatoxin B1).
Symptoms result in convulsions, followed by death, with the purplish coloring of the legs and beak.
The lesions found at autopsy are as follows:
■ large, dark red liver with discolored patches;
■ hemorrhage and subcutaneous edema.
Progression to cirrhosis is frequent maize poorly dried in cribs, force-feeding).
Aflatoxicosis in ducks can promote the development of hepatocellular carcinoma.
At the turkey
Acute aflatoxicosis in this species is the same as that