Pay attention to mildew prevention and detoxification of feed

Mycotoxins are secondary metabolites produced by fungi. Common molds include Aspergillus, Fusarium and Penicillium, which can grow on crops during crop growth and harvest and after processing. Mycotoxins are not only toxic to livestock and poultry, but also endanger human health through the food chain. At present, the most important thing to prevent and control the harm of mold and mycotoxin is to do well the two links of mildew prevention and detoxification of feed.

First, feed anti-mildew

1. Reduce pollution. When purchasing raw materials, it is necessary to strengthen inspection and acceptance, prevent moldy raw materials from entering the factory, keep feed warehouses, processing and transportation equipment clean and pollution-free, regularly check and clean some parts of the production line that are prone to long-term residual feed, and thoroughly clean the moldy and caked feed.

two。 Control the water content of raw materials and keep the environment dry. It is generally required that the water content of feed raw materials should not exceed 13%, and feed raw materials with excessive water content should be dried in time. The warehouse for storing feed should be dry, the bottom should be at the bottom during storage, and the space should be left around the top to make the air circulate. For those who have been stored for a long time, moisture should be monitored regularly, and measures should be taken in time if the water content exceeds the standard.

3. Appropriate addition of mildew agents and antioxidants. Anti-mildew agent can inhibit the reproduction, growth and toxin production of mold by destroying the cell wall or intracellular acid. When the water content in feed is higher than the upper limit of safe storage moisture content, anti-mildew agent can be considered. At present, propionic acid and its salts (calcium propionate, sodium propionate and potassium propionate) are commonly used as anti-mildew agents, the addition amount of propionic acid is 0.3% of feed, and the addition amount of calcium propionate is 0.2%-0.5% of feed. The use of anti-mildew agent in feed is mainly determined according to season and moisture content. In dry and cool seasons such as autumn and winter, when the feed moisture is less than 11%, it is generally not necessary to use anti-mildew agent; when the moisture content exceeds 12%, anti-mildew agent should be used, and the amount of anti-mildew agent should be increased in high moisture content and high temperature and high humidity season. The mildew process of feed is also accompanied by the oxidation process of nutrients in feed. General antimildew agents should be used together with antioxidants to form a complete anti-mildew and antioxidant system in order to effectively prolong the storage life.

4. Reasonable storage of feed. Loading feed to prevent rain and sun, storage feed warehouse should be ventilated, cool, dry and high-lying, there should be brackets at the bottom to isolate the ground, regular disinfection, cleaning and rat prevention. Stacking should be standardized, if the ambient temperature is higher than 10 ℃, the stacking height shall not exceed 14 layers (bags). The material pile should keep a certain distance from the window and wall, and pay attention to the preservation time should not be too long.

2. Detoxification of feed

Feed mildew, especially a large number of feed raw materials mildew, all discarded will suffer heavy losses, but if mildew is very serious, it should be abandoned, because its nutrients have been seriously lost, for mildew feed and raw materials, then according to the specific situation, different methods are used for detoxification, generally physical detoxification, chemical detoxification, enzymatic hydrolysis and adsorption.

1. Physical and chemical detoxification. Physical detoxification methods mainly include washing method, elimination method, embryo detoxification method, solvent extraction method, heating detoxification method and radiation method, while chemical detoxification mainly uses alkali or oxidant for detoxification. Many of the above detoxification methods are not applicable in practical application and for the current feed industry and aquaculture industry, because they are not only difficult to operate, but also often reduce the nutritional quality and palatability of feed after chemical detoxification.

two。 Enzymatic hydrolysis. The main purpose of this paper is to select some enzymes and make use of their degradation to destroy mycotoxin or reduce its toxicity. compared with physical and chemical methods, enzyme degradation treatment has less loss and effect on feed nutrients, but there are three problems in practical application: first, the enzyme is not heat-resistant and easy to be inactivated at high temperature, and the production process of feed products, especially pressed pellet feed, needs to go through high temperature. Second, the cost of enzymatic detoxification is high and it is generally difficult to accept. Third, when using enzymes to degrade the toxicity of mycotoxins, some mycotoxins need a complete set of enzymes to completely degrade their toxicities. For example, when zearalenone is degraded, some enzymes only convert it into another substance, but the transformed substance is still toxic and requires a series of enzymes to completely degrade it into non-toxic substances. This series of enzymes are still in the research stage.

3. Adsorption. That is, a method of detoxification by adding mycotoxin adsorbent to feed. This method is still feasible (it has been widely used abroad). Suitable adsorbents should be selected in actual production, which can not only effectively reduce the harm of mycotoxins to animals, but also avoid negative effects on animal growth. The ideal adsorbent should have the ability to adsorb different kinds of mycotoxins; the amount used is low and effective; it can be quickly and uniformly mixed in feed for granulation, expansion and storage; it has no adsorption to vitamins, trace elements, drugs and other nutrients; it has high stability in a wide range of pH and should be biodegradable after discharge; it should be free of pollutants.

At present, the mycotoxin adsorbents with better detoxification effect in feed are aluminosilicate, organic compounds (yeast cell wall, etc.) and other resins (anticholamine, etc.). Natural aluminosilicate, such as zeolite, montmorillonite, diatomite and kaolin, etc., aluminosilicate adsorbents have good adsorption capacity for aflatoxins, but they have insufficient adsorption capacity for toxins such as zearalenone, ochratoxin and monosporin. Esterified glucomannan (EGM) is a new type of mycotoxin adsorbent, which is a functional sugar extracted from yeast cells. Its surface is rich in holes with different pore sizes, which can be used to capture different kinds of mycotoxins in a large area. Therefore, EGM has a strong adsorption effect on a variety of mycotoxins, and the adsorbed mycotoxins are not easy to dissociate, have no significant side effects on other nutrients in feed, and may also have a positive effect on other physiological functions of animals, so it is a broad-spectrum mycotoxin adsorbent with great potential.