Antibiotics in animal production

The advisability of using certain antibiotics, particularly penicillin and tetracycline, in animal feeds has been questioned because of their use in human medicine. Any use of an antibiotic that is prescribed for humans presents some risks to human health, whether the use is for humans, animals or for other purposes but. the uses also have benefits. Otherwise, they would not persist. Antibiotics are used in animal feeds to increase animal weight, increase efficiency of feed utilization, increase reproductive efficiency and decrease morbidity and mortality. These benefits to animals and animal producers are reflected in decreases in food costs to humans. There are also benefits to human health from use of antibiotics in food animals. By reducing the incidence of animal health problems, use of antibiotics in food animals reduce the transference of animal infections to humans. The contention that the effectiveness of penicillin and tetracycline for use in human medicine is rapidly diminishing as a result of the proliferation of resistant bacteria caused by subtherapeutic use of antibiotics in animal production is not supported by experimental data. Rather, the evidence suggests that a fairly stable level of resistance of the intestinal bacteria in humans has long since been established to penicillin and tetracycline as it has been in animals. 

Why J he Concern About Using Antibiotics In Animal. Production ... 

AD Cooper, GWF Stubbings, M Kelly, JA Tarbin, WHH Farrington, G Shearer. Improved method for the online metal chelate affinity chromatography high-performance liquid chromatographic determination of tetracycline antibiotics in animal products. J Chromatogr A 812 321-326, 1998. 

Antibiotics are routinely added to animal feed in conventional agriculture. This can have various effects on humans. Direct transmission of antibiotic residues in animal products to people may cause direct toxicity, i.e. allergies, or lead to the emergence of resistant strains of bacteria. Another threat is antibiotic-resistant forms of bacteria harmful to mankind that might appear in animals and pass from them to humans (Smith 1974), or may impart resistance to other bacteria by plasmid or transposon interchange (Franco et al. 1990). The resulting dmg-resistant and harmful micro-organisms can then not be treated successfully (Silverstone 1993). 

This overview has presented an introduction to the subject of antibiotics in animal agriculture and provides a general view of the extent of antibiotic use. The manuscripts to follow will offer more details and provide additional food for thought. Certainly the current efficient production of meat and dairy products is dependent on a wide variety of antibiotics and this will continue to be true in most Western countries in which livestock production is an important part of the economy. 

Three broad groupings, of the antibiotic substances presently used in animal production, include (a) broad-spectrum antibiotics, including penicillins and tetracyclines, which are effective against a wide variety of pathogenic and non-pathogenic bacteria (b) several narrow-spectrum antibiotics that are not used in human medicine and. (c) the ionophore antibiotics, monensin. lasalocid and salinomycin Monensin and lasalocid are used as rumen fermentation regulators in beef cattle, and the three ionophores are used as coccidiostats in poultry production. The ionophores. which are not used in human medicine, were first introduced in the 1970 s and account for most of the increase in antibiotic usage in animal production since the 1960 s. 

The risk that exists from the use of antibiotics in animals arises through a complicated series of events. When an antibiotic is fed to an animal, it comes in contact with the vast and complex bacterial population in the digestive tract. If present in biologically effective amounts, it affects the sensitive bacteria, which may include pathogens but, the total number of living bacteria remains about the same. The sensitive bacteria destroyed or inhibited, and the resistant bacteria multiply to take their place. These resistant bacteria may contaminate animal products used by humans as food. 

In 1971, Great Britain implemented a ban on subtherapeutic use of tetracyclines in animal production. This action was taken after considerable debate and was greatly influenced by antibiotic resistant Sa Imone 1 la infections (S. typhimurium phage type 29) in humans in the mid-1960 s, which appeared to be related to similar infections in calves (Anderson, 23 Antibiotics were not approved as feed additives for calves at that time nor previously. Thus, earlier implementation of the Swann Committee (Ifi) recommendations would have had no apparent impact on that particular epidemic, nor did it prevent a similar epidemic later (Rowe et al., 12J. 

In the decade of the 1950s, the use of antibiotics in animal feeds led to improvements in animal health and animal production. This contributed to the rise of large units for maintaining meat animals and poultry. These first 10 years should have given ample time for resistant pathogens to have become widespread. Ten years of this spread of resistance ought to have made antibiotics in animal feed useless or deleterious so that their commercial use would cease. Yet this has not happened, even after 35 years. The failure of such a series of events to take place is an unexplained riddle. 

As a result of FDA s proposals and the need for more information, a committee was appointed by the National Academy of Sciences. Its report (376 pp) was published in 1980 as "The Effects on Human Health of Subtherapeutic Use of Antibiotics in Animal Feeds" (7). The report noted that the use of antimicrobials in animal husbandry has steadily increased since 1950, as has animal production. Antimicrobials are perceived as especially beneficial when animals are being reared under... 

Some other antibiotics commonly used in animal production such as the bacitracins, bambermycins and virginiamycins as well as the streptomycins are poorly absorbed from the intestinal tract and residues usually do not occur from feeding. Chloramphenicol is used illegally in the United States in many species it is used legally in Europe, Canada and other parts of the world. 

Approximately 19 million pounds of antibiotics are used each year in U.S. cattle, hogs, poultry, and other food animals this is over 40% of the antibiotics sold in the U.S. (17). The routine use of antibiotics on farms to accelerate growth and prevent diseases has been speculated to have created strains of disease-causing bacteria that are resistant to antibiotics, which in turn infect more human beings every year (18). Because of the widespread use of antibiotics in livestock production, it would not be surprising to see antibiotic contamination of the aquatic environments situated near animal feedlots and confinements. The presence of antibiotics in water resources is suspected to contribute to the proliferation of resistant microorganisms, ft is not clear how much of these chemicals finds its way into the surface water near livestock operations. 

Apart from public health impacts, residual antimicrobials in animal products can bring about technoeconomic losses in the food processing industry. It has long been known that the presence of some antimicrobial compounds in milk can dramatically affect the production of fermented dairy products such as yogurt, cheese, buttermilk and sour cream (72, 73). As shown in Table 10.2, even minute concentrations of antibiotics in milk can cause inhibition of the growth of commonly used dairy starter cultures (74). 

T.-C. Chung, in An examination of Antibiotic Residues in Animal Products Marketed at the Middle Area of Taiwan, Department of Veterinary Medicine, National Chung Hsing University, Taiwan (1986). 

Coupling of liquid chromatography with mass spectrometry provides unequivocal online spectrometric identification of tetracycline antibiotics in animal-derived foods. Typical applications of mass spectrometry in confirming tetracycline residues in edible animal products describe coupling of liquid chromatography with mass spectrometry via particle-beam (280), electrospray (292), or atmospheric pressure chemical ionization (307), using negative-ion detection interfaces. 

LC-MS plays an important role in the confirmation of identity of the veterinary residues of antibiotics in animal food products for human consumption [3-6]. LC with UV or UV-DAD detection is often apphed in quantitative determination, while confirmation of identity is performed by LC-MS. GC-MS is applicable to a limited number of compound classes after derivatization. The LC-MS characterization of various classes of antibiotics is discussed in this section, while residue analysis is discussed in Ch. 14.3. An overview of important classes of antibiotic and antibacterial compounds is given in Table 14.1. Typical examples of various compound classes are shown in Figure 14.1. Only a limited number of compound classes is discussed here. 

Many factors influence the residue profiles of antibiotics in animal-derived edible tissues (meat and offal) and products (milk and eggs), and in fish and honey. Among these factors are the approved uses, which vary markedly between antibiotic classes and to a lesser degree within classes. For instance, in some countries, residues of quinolones in animal tissues, milk, honey, shrimp, and fish are legally permitted (maximum residue limits [MRLs] have been established). By comparison, the approved uses of the macrolides are confined to the treatment of respiratory disease and for growth promotion (in some countries) in meat-producing animals (excluding fish), and to the treatment of American foulbrood disease in honeybees. As a consequence, residues of macrolides... 

The cost of developing new antibiotics due to over-use in animal production ... 

Lower efficacy of antibiotics will not only effect livestock production, as several studies have shown development of antibiotic resistance in humans. Antibiotic residues in animal products may be linked to consumer health and have been associated with the following problems ... 

It can be concluded from this research that increased use of antibiotics as growth promoters (AGPs) for livestock production, both in pig and poultry farming, can result in a high percentage of resistant bacterial strains, especially E. coli. This not only affects animal production, but may have an impact on human medicine too. As a result, a cutback in the use of AGPs in animal production has been recommended and since January 2006 in EU countries, they have been banned. 

Gallois, M., H. J. Rothkotter, M. Bailey, C.R. Stokes and I.P. Oswald, 2009. Natural alternatives to in-feed antibiotics in pig production can immunomodulators play a role Animal 3, 1644-1661. 

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