Not long ago, the European dioxin-contaminated feed incident gave the feed industry a warning that feed antibiotics were once again raised and became one of the evidence that the feed industry might contaminate the food chain. Studies have confirmed that despite the resistance and residues of feed antibiotics, the correct application has not found direct evidence of harm to human health.
1. Mechanism and effect of antibiotics
1.1 Mechanism of action
The essential properties of antibiotic activity: can be properly taken into the body and distributed in the body; can penetrate into the microorganism; have a selective effect on the target organelle in the cell. The mechanism of action is: inhibiting bacterial cell wall synthesis, impairing bacterial cell membrane, interfering with nucleic acid metabolism; interfering with the expression of genetic information, inhibiting protein synthesis, and inhibiting gene function.
1.2 The actual effect of
NRC (1998) summarizes the effects of antibiotics on improving pig growth rate and feed conversion efficiency. In 1194 trials (32555 total), antibiotics increased the growth rate of weaned pigs, growing pigs, and fattening pigs by 16.4, 10.6, and 4.2%, respectively. Feed conversion efficiency improved by 6.9, 4.5 and 2.2%, respectively. At the same time, the use of antibiotics is inversely proportional to the environmental quality, that is, as the environmental quality improves, the effect of antibiotics to improve growth performance is getting smaller and smaller.
2. Antibiotic resistance drug
The presence of antibiotic resistance has been demonstrated in the United States. The study believes that the abuse of antibiotics may accelerate the elimination of allergenic bacteria, while drug-resistant bacteria survive. Drug resistance is transmitted through gene expression and plasmids (the presence of antibiotic resistance has been demonstrated in the United States. Studies suggest that antibiotics may be eliminated by the abuse of antibiotics, while drug-resistant bacteria survive. Drug resistance is transmitted through gene expression and plasmids (R - Factor), which is more threatening. On December 14, 1998, EU member states (except Spain, Portugal and Belgium) banned the addition of virginiamycin and spiramycin to feed. Antibiotics.
Sweden banned the addition of antibiotics to feed in 1986, but in 1998 it was found that piglets had an increased diarrhea rate; mortality increased by 1.6%; up to 25 kg of body weight required to consume 5.2 days; NE feeding on NE was difficult to prevent and treat; The demand is greatly improved; the therapeutic dose is greatly increased, and the total antibiotic use in the country in 1988 and 1995 is not much different.
3. Selection of commonly used antibiotics
Feed antibiotics are generally used in small amounts to prevent disease and promote growth. Its use effect is affected by many factors, such as feeding objects, growth stages, types of antibiotics, feeding environment, dietary ingredients, antibiotics and compatibility with other drugs.
3.1 Livestock and poultry species, different stages of livestock and poultry in different stages of growth, different growth stages, different physiological conditions will affect the effect of feed antibiotics. It is generally believed that the growth-promoting effect of feed antibiotics is more obvious in the young stage of livestock and poultry, and the growth-promoting effect gradually decreases or disappears with the increase of age.
3.2 Different types of antibiotics for feeding have different effects on antibiotics, and the same antibiotics have different effects under different test conditions and production conditions.
The bacitracin is a white or light yellow powder, an unstable polypeptide obtained by fermentation of Bacillus licheniformis, containing various components, mainly composed of A. In production, it is prepared by adding ZnSO4 when the bacillus is fermented and the bacillus peptide has the highest titer. If calculated according to A, it contains about 7% zinc. Zinc bacitracin can be used in pigs, chickens, cattle and other livestock, and can even be used in laying hens. Large doses may damage the kidneys. The amount prescribed in China is: the addition of 4 parts per million to 40 parts per million for pigs; the addition of 4 parts per million to 20 parts per million for chickens;
Virginiamycin virginiamycin contains M1 body, S1 body, M1 is a macrolide, and S1 is a cyclic polypeptide. When M:S=70:30, the antibacterial activity is the highest. Virginiamycin is not easily absorbed by the intestines and has little residue. The US prescribed dosage is: pigs add 10 to 20 parts per million, and pigs weighing more than 45 kg are forbidden to use; chickens are added to 2 parts per million to 5 parts per million, and laying hens are banned, but the European Community Allow it to be used in laying hens.
Tylosin is easily distributed throughout the body; low blood concentration; high concentration in organs; and macrolides (except leucomycin), resistance between macrolides and lincomycin . In the case of poor sanitation and imbalanced diets, the effect is greater. The amount of supplements prescribed in China is: the number of pigs within 4 months of age is increased by 10 parts per million to 100 parts per million, and the pigs of 4 to 6 months old are added to 5 parts per million to 20 parts per million; 8 weeks Chickens within the age of 10 to 50 parts per million, 5 days before slaughter.
Advantages of flavomycin: low toxicity, no side effects, and basically no residue. It is mainly effective against Gram-positive bacteria. Flavomycin is not absorbed in the digestive tract. It is a good feed additive. It has a long application time and wide range, and has effects on cattle, pigs, chickens and rabbits. The US FDA regulates broilers from one part per million to two parts per million; pigs, two parts per million to four parts per million. The usage in Japan is: chicken, 5 parts per million to 5 parts per million; lactating pigs, 5 parts per million to 20 parts per million; piglets, 1 part per million to 10 parts per million .
Chlortetracycline is a broad-spectrum antibacterial drug. Chlortetracycline inhibits harmful microorganisms and promotes the growth of beneficial microorganisms, thereby increasing the growth rate of livestock and poultry, improving feed efficiency, and enhancing the ability of the small intestine to absorb nutrients. Japan and the United States are allowed to use, and the approved use amount is: suckling pigs, millions of points. Ten to one hundredth of a million; cattle are limited to 6 months of age, adding 10 parts per million to 50 parts per million, and stopping 48 hours before slaughter.
4. Formulator's expectations
The addition of antibiotics to the diet generally promotes growth, but is also affected by the type of diet. For example, the non-starch polysaccharides of wheat can cause an increase in the number of Clostridium perfringens in the intestines of livestock and poultry, and the addition of antibiotics (zinc bacitracin) can inhibit the proliferation of Clostridium perfringens in the intestine.
In addition, it is often necessary to pay attention to the incompatibility and combination of antibiotics. The emergence of alternatives, the intervention of nutrition, pharmacology, and sociology will also have a major impact on the choice of antibiotics by formulators.
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