Antibiotic feed additives

Antibiotic feed additives, antibiotic resistance controversy, 5-6 Antibiotic growth effect characteristics, 113t vs. contamination, 113,1l4t vs. disease level, 1l4-115t Antibiotic residues... 

The tetracyclines have been used extensively for agricultural purposes as animal feed additives however, their use has been discontinued in England on evidence of the report of the Swann committee s. This recommendation was based on findings that the bacterial flora of animals fed tetracyclines (and other antibiotics) on a continuous basis contained a high proportion of strains carrying R-factors. Such animals constitute a reservoir of resistant strains which may be passed to human subjects and possibly transmit their resistance characters to antibiotic sensitive pathogens. There is no direct evidence that such transfer occurs, but there is little doubt that the extensive use of antibiotics selects for an antibiotic-resistant population of bacteria among cattle, poultry, swine and fish which have been maintained on antibiotic feed additives . 

Veterinary Applications. Another use for antibiotics is for veterinary appHcations and for animal feed supplements to promote growth in Hvestock (see Feeds and feed additives). Feed antibiotics used in the United States far surpass all other agricultural appHcations in terms of kilogram quantities used and approach quantities used in human medicines (25). In 1980 the USA feed antibiotic usage was estimated to be between five and six million kg. The U.S. Council of Agricultural Science and Technology estimates that feed additives save the U.S. consumer approximately 3500 million per year in meat prices, and antibiotic use accounts for most of this. 

Thiostrepton family members are biosynthesized by extensive modification of simple peptides. Thus, from amino acid iacorporation studies, the somewhat smaller (mol wt 1200) nosiheptide, which contains five thiazole rings, a trisubstituted iadole, and a trisubstituted pyridine, is speculated to arise from a simple dodecapeptide. This work shows that the thiazole moieties arise from the condensation of serine with cysteiae (159,160). Only a few reports on the biosynthesis of the thiostrepton family are available (159,160). Thiostrepton is presently used ia the United States only as a poly antimicrobial vetetinary ointment (Panalog, Squibb), but thiazole antibiotics have, ia the past, been used as feed additives ia various parts of the world. General (158) and mechanism of action (152) reviews on thiostrepton are available. 

The polyether antibiotics were first recognized as a separate class with the pubHcation of the structure of monensia ia 1967 (1). Several members of the group have siace found commercial appHcation as anticoccidials ia poultry farming and ia improvement of feed efficiency for mmiaants (see Feeds and FEED additives). 

Oxytetracycline is a broad-spectrum antibiotic, which has been used worldwide in veterinary medicine and in aquaculture for the prevention and treatment of disease and as feed additives to promote growth. The maximum residue limits (MRLs) of OTC and relative substances as described by the US Food and Drug Administration [66] and European Union [67] are presented in Table 4. 

Collinder E., Berge G.N., Cardona M.E., Norin E., Stern S. and Midtvedt, T. (2000). Feed additives to piglets, probiotics or antibiotics , in Proceedings of the 16th International Pig Veterinary Society Congress, Melbourne, Australia. 17-20 Sept. 2000, pp 257. 

Since the discovery of penicillin, an enormous number of antibiotic compounds have been isolated. They have found uses both in treatment of human disease and in various aspects of agriculture, including treatment of animal and plant diseases, and as feed additives to promote growth of animals. Some antibiotics such as tylosin were developed specifically for agricultural use. 

This book was developed to provide a current perspective on agricultural use of antibiotics. Topics include some major uses of antibiotics, problems associated with their use from a regulatory standpoint, residues in food including methods of detection, risks to human health from use in feeds, trends in use, and overall risks and benefits. The scope, therefore, is much broader than in several other recent symposia that have focused mainly on the controversy regarding the use of antibiotics as feed additives. Many of the topics included in the present volume have not been discussed under one cover before. 

Although the feed additive uses of antibiotics have been emphasized, it should be noted that the uses as injectables for therapy, mammary infusions for mastitis, boluses, pills, capsules, medicated blocks, and drinking water formulations include a wider variety of antibiotics than are added to feeds. Many of these are currently used at the discretion of the meat producer or dairyman, others must be used under the direction of a veterinarian. For example, chloramphenicol is an antibiotic which the veterinarian has access to, but which the FDA has indicated should not be used in livestock destined for human consumption, primarily because of the... 

By far the largest agricultural market for antibiotics is for feed additives. The bulk of this market is taken by antibiotics that are also used in human medicine. However, mounting concern over the hazards of increased resistance to antibiotics has encouraged the search for new types of antibiotics for this use. 

The market for animal health products is estimated to be over 2 billion in the U.S, and nearly as much in Western Europe Antibiotics dominate the animal health market, and feed additives account for about 50% of that market. 

Feed Additives. Some antibiotics are also administered in the feed for the treatment of disease. These are listed in Table III. For the most part, they are used for the treatment of bacterial infections and are the same as those listed in Table II. Although these antibiotics are incorporated into the feed, their use differs from what has become known as "feed additive antibiotics" or growth permittants. 

The era of feed additive antibiotics had its beginning in the late 1940 s in a classic example of serendipity. Investigators at the Lederle Laboratories were searching for a more convenient source of "animal protein factor", a substance found in liver and other animal proteins that stimulated the growth of chicks fed a vegetable diet (1). [It had already been demonstrated by workers... 

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