① Antibiotics can inhibit and kill some pathogenic bacteria, improve animal resistance and prevent diseases. This is the guarantee for the healthy growth of animals.
(2) Adjust the microbial flora in animal intestines, inhibit unfavorable microorganisms, stimulate beneficial bacteria and reduce the loss of nutrients.
③ Thinning the intestinal wall of animals and improving the absorption rate of nutrients.
④ Slow down the intestinal peristalsis, ensure the digestion and absorption time of nutrients in the intestine, and improve the digestion and absorption capacity. ⑤ Stimulate animal appetite, increase feed intake and promote animal development. Long-term use of antibiotic feed additives will cause the following problems:
① Drug resistance: After long-term use of an antibiotic additive in livestock and poultry, the pathogenic bacteria produce drug-resistant strains. Under certain conditions, the drug-resistant genetic factor (also known as R "factor") can be transferred to other sensitive cells, making some drug-resistant pathogenic bacteria become drug-resistant strains, which brings troubles to the prevention and treatment of livestock and poultry diseases. For oxytetracycline, penicillin, streptomycin and other antibiotics used for people and livestock, if drug-resistant strains appear, it will affect the prevention and treatment effect of human diseases and cause adverse consequences.
② Antibiotic residues in livestock and poultry products. Some antibiotics are easily absorbed by animal intestines, excreted slowly and remain in meat, eggs and milk. These antibiotics are not easy to be completely "passivated" during food heating or cooking. Some antibiotics have mutagenic, teratogenic and carcinogenic effects.
Therefore, when using antibiotic feed additives, we should pay attention to the following matters:
(1) Select a variety that is special for livestock and poultry, has poor absorption, little residue and does not produce drug resistance. There are many laws and regulations on this, such as the feed safety regulations in Japan and the federal Food and Drug Administration (FDA) regulations in the United States. ② Strictly control the dosage, so as to achieve the use effect with as little dosage as possible. Many antibiotics have different effects on preventing and treating diseases and promoting growth, and their doses are obviously different.
③ Duration of antibiotic use. Animals use different species at different growth stages, and more attention should be paid to withdrawal period. Generally, the drug should be stopped 7 days before slaughtering meat animals.