1. The cause of feed halal taste
The feed is prone to spoilage and deterioration during processing, transportation and storage, resulting in an unpleasant smell, commonly known as halal (the most common in feed mills is oxidative rancidity).
The reason, on the one hand, there are often volatile metals (Fe, Cu, Zn, etc.) or free radicals and enzymes formed by photooxidation in feeds. These substances become the inducers of feed oxidative rancidity, lipids and oxygen. These inducers react to form aldehydes, ketones, acids, and alcohols, which give the feed an unpleasant scent. On the other hand, lipoxygenases present in plant feed or lipoxygenases produced by microorganisms are most susceptible to oxidation of unsaturated fatty acids. When the water content of the fat in the feed exceeds 0.3%, the microorganisms can decompose, and the fat molecules are decomposed into fatty acids and glycerin. If sufficient oxygen is present at this time, the carbon chain in the fatty acid will be oxidized and broken, and finally completely oxidized to CO2. And water, so that the nutritional value and palatability of the feed decline, and produce a series of toxic effects.
2. The hazard of
2.1 affect the economic benefits of the feed mill. Once the feed produces odor, it will inevitably affect the sale of feed and cause economic losses to the feed mill.
2.2 Reduce the palatability and nutritional value of the feed. The smell of the pig is very sensitive. The smell of the feed will reduce the feed intake, and the rancidity of the oil will cause the destruction of certain nutrients, affecting the absorption of the B vitamins. The long-term consumption of the animal will produce essential fatty acids and vitamin deficiency, such as the brain. Softening, infertility or gestational abortion and overall performance and resistance are reduced. Affect the body's enzyme activity, causing metabolic disorders, making growth retardation; reducing animal immune function; affecting digestion and absorption. After the animals ate oxidized rancid feed, the overall performance was decreased food intake, slower weight gain, and lower feed returns.
2.3 Destructive effects on pigments such as lutein. Oxidation products have an adverse effect on the absorption and deposition of lutein, resulting in poor coloration of egg yolk and broiler skin and ankle.
2.4 Oxidation of rancid products reacts with active amino acids in the feed. In particular, after reacting with methionine, lysine, cystine, etc., the nutritional value of the feed is lowered, and the animal may even endanger the health after eating.
3. Preventive measures
3.1 Improve feed formula and feed processing technology
3.1.1 Carefully select feed ingredients. Feed ingredients have an important impact on the oxidative rancidity of the feed, especially the type and content of lipids in the feed and the degree of unsaturation of the lipid itself. Studies have found that the higher the degree of unsaturation of fats and oils, the lower the degree of refining, the more likely it is to produce oxidative rancidity. The feed ingredients are granulated or hydrogenated to reduce the possibility of oxidative rancidity in the feed.
3.1.2 Reasonably determine the amount of trace elements added. In the preparation of feed formula, it is necessary to consider the nutritional effects of trace elements such as Fe, Cu and Zn, and also consider its impact on feed preservation, reasonable ratio, and find the optimum amount of trace elements. To control the use of high copper, high zinc, high iron. It is preferred to use a trace element chelate when using a trace element additive. It should also be noted that if high copper is used in the concentrate or batch, the use of granular copper should be used to avoid the use of powdered copper, which also reduces the auto-oxidation catalyst effect of trace elements.
3.1.3 Reasonable selection and matching vitamins. Adding vitamin A, vitamin E and vitamin C to the feed can effectively protect the fat from oxidation. According to Li Junsheng et al. (2003), vitamin E is used in combination with vitamin C or citric acid, and its antioxidant effect is better.
3.1.4 Reasonably add appropriate amount of antioxidants. The addition of antioxidants can effectively prevent lipid oxidative rancidity, and the amount and type of additives are the determining factors of oil stability. The optimum concentration of antioxidants is 0.02%. Too high or too low will result in increased grease instability (except for terpenoid antioxidants).
3.1.5 Regularly clean the oil tanks and mixing tanks to prevent microbial growth and long-term retention of feed on the wall.
3.1.6 Pay attention to the storage time of raw materials. Raw materials such as soybean meal, cotton aphid and corn gluten meal should not be stored for more than 2 months in summer and no more than 3 months in winter. For bran, rice bran, DDGS and other raw materials, the storage time in summer is controlled within 15 days and within 2 months in winter. The storage time of relatively stable raw materials such as stone powder and hydrogen calcium can be longer and controlled within one year.
3.2 Improve the storage environment and control the rancidity conditions
3.2.1 Reduce the storage temperature.
3.2.2 Control the moisture of the feed ingredients, reduce the water content of the feed, and reduce the hydrolysis and rancidity of the oil.
3.2.3 Reduce the oxygen content in the feed packaging. The storage room or the packaging bag can be filled with CO2, N2, etc., and the sealing technology is used to make the environment lack oxygen, prevent free radicals and microorganisms from secreting lipase, and can effectively prevent oxidation and rancidity of the oil. This technology is economically limited and has few applications.
3.2.4 Keep away from light. This can reduce the rancidity of the oil caused by ultraviolet radiation. In addition, light can destroy VA, VE and β-carotene in the feed, which reduces the antioxidant performance and increases rancidity. Tests have shown that storing and transporting food in green packaging bags is a simple way to prevent lipid oxidative rancidity.
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