Food safety of animal feed and animal products: current situation and Countermeasures

Introduction: in the past half century, the world's animal husbandry has made great progress Animal husbandry has made great contribution to meet the demand of human animal food However, animal husbandry is still an inefficient industry The efficiency of transforming feed nutrients into animal products is 15% - 20%, 80% - 85% of which is discharged into the environment, causing huge pollution to the soil, air and water source (the pollution of N and P is the most serious) In order to improve the level of animal production and feed conversion efficiency, animal properties such as meat and bone meal, oil and fat, and growth promoters such as antibiotics, high copper and arsine preparations were widely used in the feed process In recent years, due to the improper handling and use of these raw materials or long-term use and abuse, a series of food safety incidents related to feed have occurred one after another, including the occurrence and spread of mad beef, dioxin E.coli and mycotoxin poisoning, antibiotic resistance, production and transfer in Yinghe 0157 not only have given the countries and regions concerned the serious economic losses, but also have developed into social and political issues of global concern It can be seen that to solve the problem of the safety of livestock products and the environmental pollution caused by livestock production has become a common voice and an important topic in the world, and the production of pollution-free green livestock products has become the basic requirement for the sustainable development of animal husbandry The production of high-quality green livestock and poultry products depends on the application of green (pollution-free) feed and feed additives as well as production technical regulations ① Obviously improve the performance of animal production; ② no residue in animal products, no adverse effect on the natural flavor of animal products, no potential harm to human health; ③ no pollution to the environment In order to make animal husbandry a green industry, various countries have formulated corresponding feed safety regulations and strengthened the research and development of new feed technology and new products This paper summarizes the main problems in feed safety and puts forward the main ideas to solve the problems 3221 The main unsafe factor in the feed 1.1 Meat and bone meal and BSE 322 BSE is called "bovine spongiform encephalopathy" It occurs in cattle with progressive central nervous system disease Its symptoms are similar to those of pruritus The cause of the disease is that cattle are fed with meat and bone meal made of sheep with pruritus The meat and bone meal contains a peculiar pathogenic factor, which is called "disease factor of cattle" "BSE factor" is neither a bacterium nor a pathogen, but an abnormal protein Conventional measures to control the disease are not effective for BSE The spread of BSE is mainly due to the large-scale production of meat and bone meal BSE has the highest incidence in the UK, accounting for 99% of the total in 1999 By July 2000, more than 176000 cattle in more than 34000 pastures in the UK had been infected with the disease The highest incidence was in 1993, with at least 1000 cattle infected each month Later, other European countries also found the local BSE At present, the incidence of BSE in the world has increased to nearly 20 countries 322 BSE belongs to "transmissible spongiform encephalopathy "Humans also have this disease, known as Creutzfeldt hajkd duease (CJD) The natural incidence rate of the disease is one in a million The patient is 50~70 years old The patient is suffering from brain damage, dementia, and complications After 1995, the "new variant of Creutzfeldt Jakob disease" (vccd) was found in the UK The patients showed depression, inability to walk, dementia and finally death It has been confirmed that vccd is closely related to the outbreak of BSE According to the comprehensive research of the World Health Organization, the brain, spinal cord, cerebrospinal fluid and eyeball of the diseased cattle are highly infectious; the small intestine, dorsal root ganglion, bone marrow, lung, liver, kidney, spleen, placenta and lymph nodes are also infectious After humans eat these tissues or other foods contaminated with BSE, they are infected through the digestive tract The infective factors first enter the local lymphoid tissue and proliferate in it, then appear in the spleen and tonsil, and finally locate in the central nervous system At present, there are more than 80 patients with vCJD in the UK, 2 in France and 1 in Northern Ireland The age of patients is from 16 to 75 According to one study, the number of people infected with vCJD in the UK has exceeded 80000 (Ministry of health document, 2001) 3221.2 dioxin pollution: dioxin is the general term of polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans There are 210 kinds of isomers, which are formed due to the different substitution number and position of chlorine atoms Dioxins come from incomplete combustion of organic compounds Among them, incineration of municipal solid waste and iron and steel smelting are the main sources of dioxins (Zhang Jie et al., 2000) According to the report released by the United Nations Environment calculation agency, among the 15 major developed countries in Europe and the United States, Japan's dioxin emissions are 4000g / year, the United States' is 2744g / year, Sweden's is the least, 22G% Dioxin has stable chemical properties, does not react with acid and alkali, is not easy to decompose, is not easy to burn, and is insoluble in water After entering the body, it is almost not excreted and deposited in the liver and adipose tissue Dioxin is a highly toxic substance, and its carcinogenic toxicity is 10 times higher than that of Xanthotoxin Among them, 2,3,7,8-dioxins replaced by chlorine atoms are the most toxic, 1000 times higher than potassium cyanide After dioxin enters the body, it changes the normal structure of DNA, destroys the function of gene, causes deformity and canceration, disrupts endocrine function, damages immune function, reduces fecundity and affects intelligence development The lowest dose of dioxin induced acne chloride is 824 μ g / kg fat, the dose of hepatoma is 10 μ g / kg body weight, and the lethal dose is 4000 μ g / kg ~ 6000 μ g / kg body weight 3221.3 the safety of hormone growth promoters 1.3.1 clenbuterol poisoning 322 clenbuterol is a synthetic β - stimulant β - stimulants are a kind of phenylethanolamine compounds with similar chemical structure and pharmacological properties to adrenaline There are many kinds of β - stimulants, including clenbuterol, cimaterol, ractopamine, sallbuta mol, among which clenbuterol has the lowest cost and the highest efficacy As a feed additive, clenbuterol can improve lean meat rate, reduce fat deposition and improve feed utilization, so it is commonly known as melting and has a strong accumulation in the body As a feed additive, it is easy to remain in animal tissues and animal products Due to the stable nature of clenbuterol, the residual animal food is easy to be poisoned, which is manifested as dizziness, nausea, vomiting, blood pressure rise, heart rate acceleration, temperature rise, shiver and other symptoms Clenbuterol was widely used as a meat additive in foreign countries around 1990 Since then, there have been many collective poisoning incidents caused by eating meat containing clenbuterol For example, according to Yang Shixing (2001), there were 135 poisoning cases in Spain in 1989, 43 poisoning cases in 1991 and 232 poisoning cases in 1992, 9 poisoning cases in France in 1990 and 26 poisoning cases in Italy in 1996 China has never approved the use of clenbuterol in animal feed, but the use of clenbuterol in feed and breeding enterprises is relatively common in the past few years, leading to a number of poisoning events In 1999, the state banned the use of clenbuterol The census in 2000 found that some enterprises are still using it illegally 3221.3.2 other hormones approved in the early years for use in beef cattle and aquatic animals, such as testosterone, progesterone, estradiol, zearalenol, and thyroid hormones such as T3, T4 and casein iodide, which are easy to remain in animal products and endanger human health, have been banned by various countries In China, it is also listed as illegal drugs, but at present, a small number of enterprises may still use them illegally The safety of 322 peptide hormones, especially recombinant porcine growth hormone (PST) and bovine growth hormone (BST), is still under discussion At present, most evidences show that the use of PST and BST has no adverse effects on human health Due to the utilization rate of PST for lean meat and feed and the use of BST for dairy animal husbandry The main reason for the non approval of the state is related to animal rights and political economy, while a safety issue is irrelevant 3221.4 antibiotic residues and drug resistance transfer Since the discovery of the role of antibiotics in promoting animal growth in the middle of the 20th century, antibiotic additives have been widely used and made a great contribution to the development of animal husbandry In improving the performance of animal production, the effect of antibiotics is incomparable to that of any other feed additive However, a large number of long-term use of antibiotics in feedstuffs has also produced worrying problems: first, drug resistance; first, residue The long-term use and abuse of antibiotic additives lead to bacterial resistance Although the transmission frequency of drug resistance factors is only 10-6, it is still common due to the large number of bacteria, rapid propagation, spread of drug resistance, and a variety of bacteria can produce multiple drug resistance In 1957, bacterial resistance cases were first found in Japan Some Shigella strains causing dysentery outbreak had more than one drug resistance By 1964, 40% of the epidemic strains had quadruple or multiple drug resistance In 1992, scientists in the United States found superbacteria in broiler feed, which is resistant to all antibiotics In clinical and epidemiological investigation, it was found that all kinds of pathogens have different degrees of drug resistance Bacterial resistance has brought great harm to human health Before the 1970s, human beings could conquer almost all the infectious diseases, but from 1980s to 1990s, the problem of drug resistance led to obvious consequences In 1972, more than 10000 people in Mexico were infected with typhoid bacteria resistant to chloramphenicol, resulting in 1400 deaths; in 1992, 13300 people in the United States died of antibiotic resistant bacterial infection Although there is no definite evidence to prove that the emergence of human resistance is directly related to the use of antibiotics in domestic animals, the long-term use of sub therapeutic doses of antibiotics has been widely concerned by the society 322 antibiotic residue in animal products is another problem in the application of feed antibiotics After being absorbed by animals, antibiotics can be distributed throughout the body, but there are many tissues such as liver, kidney, spleen, etc they can also remain in milk and eggs through the process of lactation and egg production, so as to extensively remain in animal products Wang Chunyi et al (1997) reported that the residues of tetracycline antibiotics in chicken liver, spleen, egg white and egg were 4.66mg/kg, 7.5mg/kg and 6.5mg/kg respectively, with the detection rate of 33.9%, 60% and 60% respectively; the residues of streptomycin in egg white were 0.7mg/kg, with the detection rate of 20% The residue of tetracycline greatly exceeds the maximum allowable residue standard (0.5mg / kg) stipulated by the European community Ma Beili et al (1997) detected streptomycin residues in kidney and spleen of pigs, which were 1.44mg/kg and 1.56mg/kg, respectively The detection rate was 96.4% and 100% Antibiotic residues not only affect the quality and flavor of animal products, but also are considered to be an important way of drug resistance transmission from animal bacteria to human beings 322 the extensive use of antibiotics also poses a direct threat to the health of livestock and poultry Due to the emergence of drug resistance and the decline of drug treatment effect, E.coli and staphylococcal disease have become common infectious diseases of livestock and poultry; on the other hand, long-term use of antibiotics reduces the immunity of livestock and poultry, destroys the balance of digestive tract microorganisms, resulting in endogenous infection and double infection of animals In addition, in actual production, the specified agent is not followed