Antibiotics in animal feed

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibiHty, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

Antibiotics in Animal Feeds Council for Agricultural Science and Technology, Report No. 88, March 1981. 

The current concern about subtherapeutic doses of antibiotics in animal feeds gained renewed impetus from two scientific papers (Holmberg et al.. 7 - 8). by researchers at the Centers for Disease Control (CDC) in Atlanta and a related editorial (Levy. UJ and news articles (Sun. 16-7) in scientific journals about them. 

Evidence for the demonstration of the link of subtherapeutic use of antibiotics in animal feeds to severe disease in humans was... 

Risks to Human Health from the Use of Antibiotics in Animal Feeds... 

Since 1969, the Food and Drug Administration s Center for Veterinary Medicine (formerly the Bureau of Veterinary Medicine) has had cause for concern that the subtherapeutic use of antibiotics in animal feeds may cause bacteria in animals to become resistant to antibiotics. This resistance to antibiotics is said by many knowledgeable scientists to be transferred to bacteria in humans, thus making these antibiotics ineffective in treating human bacterial infections due to compromise of therapy. For this reason, FDA proposed in 1977 to withdraw the use of penicillin in animal feed and restrict the use of the tetracyclines (chlortetracycline and oxytetracycline) to certain uses in animal feed. This talk will focus on FDA s efforts to finalize its review of the issue and present an update on the current status of the 1977 proposals. 

In a letter to Science in 1980 (O, U.S. Representative John Dingell (D-MICH) stated with respect to the debate concerning the subtherapeutic use of antibiotics in animal feeds "The science of this issue is well in hand, but we cannot call upon it to do the impossible. Twenty years of scientific investigation have identified but not quantified the risk to human health. We now face a fork in the road where prudent policy decision and not further study will be the pathfinder."... 

FDA s concerns regarding antibiotic resistance and the implications for human and animal health span some 30 years during which symposia, consultations with outside experts and task force reviews were held. Most notable among these actions was the establishment of the FDA Task Force on the Use of Antibiotics in Animal Feeds. Established in 1970 at the recommendation of FDA s Science Advisory Committee, the Task Force was asked to undertake a comprehensive review of the use of antibiotics in animal feeds. 

One of the major criticisms of FDA s scientific basis for wanting to restrict the use of antibiotics in animal feeds has been that it has not provided any specific instances of human illness due to drug-resistant pathogens that resulted from the subtherapeutic feeding of antibiotics to animals. However, individual events in the complicated sequence have been documented. Another report (12) by Dr. Scott Holmberg and others at CDC which appeared in the September 6, 1984, issue of the New England Journal of Medicine purportedly linked, for the first time, the use of subtherapeutic antibiotics in livestock feed to the development of serious drug resistant infections in humans. 

Continued unrestricted subtherapeutic use of antibiotics in animal feed increases the pool of drug-resistant bacteria in our environment. Moreover, the prospect of pathogens becoming drug resistant is, as FDA believes, a real threat to human health. 

FDA Task Force, 1972. Report to the Commissioner of the Food and Drug Administration on the Use of Antibiotics in Animal Feeds. FDA //72-6008, 23 pp. 

Since about 1952, the American public has been amply supplied with meat produced largely from animals that received feed containing antibiotics. These and other chemicals, including sulfonamides and antiparasitic drugs such as anthelmintics and coccidiostats added to feed, have saved labor, feed and space, thus revolutionizing animal agriculture. The record of safety of antibiotics in animal feed in the US has been excellent, including safety to producers and meat handlers as well as to consumers. 

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. 

The most serious association of antibiotics with salmonellosis was the 1965 outbreak in England of phage type 29 Salmonella typhimurium, resistant to tetracyclines. Six human deaths were attributed to this epidemic. It was traced to "shotgun" treatment of young calves with antibiotics followed by wide dispersal of the calves ( ). Although this epidemic did not involve the use of livestock feeds containing antibiotics, the seriousness of the outbreak led to an inquiry in the UK and a report by the Swann Committee, 1969, into this use. The report of the committee called for a stop to the use of certain common antibiotics in animal feeds in the United Kingdom. 

These examples were inappropriate. Overuse of ampicillin in medical practice was discussed by Wescoe on p. 27 of the FDA s own National Advisory Food and Drug Committee Report, on January 24, 1977. Wescoe said (speaking of antibiotics in animal feeds), "I really find it difficult to understand how you believe a hazard exists for instance, relative to Neisseria gonorrheae, where the disease is practically all human, where it has been treated worldwide for many years by ampicillin. .. and then strain to say that maybe that is in part due to subtherapeutic doses of the antibiotic in feed." Dr. Wescoe chaired the committee. 

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... 

The King County surveillance does not show a connection between the use of antibiotics in animal feed and either campylobacteriosis or salmonellosis. 

The third argument is that antibiotics in animal feeds, in veterinary prescriptions, and in human prescriptions, all contribute to resistance, and that only the first of these three uses should be discontinued This argument is challenged by results in Europe There was no decrease in resistance in coli following the ban on penicillin and tetracycline in animal feeds as enacted following the Swann report ... 

Issue Briefing Book "Subtherapeutic Use of Antibiotics in Animal Feeds" Animal Health Institute Alexandria, VA 22313, 1985, 30 pp. 

Berghman, L.R., Abi-Ghanem, D., Waghela, S.D. and Ricke, S.C. (2005). Antibodies an alternative for antibiotics Symposium antibiotics in animal feed are there viable alternatives 660-666. 

Wegener, H.C. 2003. Antibiotics in animal feed and their role in resistance development. Curr. Opin. 

A move away from antibiotics has therefore started. Bans and restrictions on antibiotics in animal feed have been implemented in many countries, while consumer demand for meat produced without the use of growth promoters has risen. However, there is a problem effective alternatives to antibiotics have been slow in reaching the market. Probiotic food supplements are seen as one solution to this problem (Flickinger et al., 2003). 

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