Antibiotics In Poultry Production

Antibiotics In Livestock And Poultry Production

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The following article is a special collaboration from AFMA (Animal Feed Manufacturers Association)
We thank their kind support.

Antibiotics have been widely used in the livestock and poultry industries since their discovery more than 50 years ago. They represent an extremely important tool in the efficient production of animal products such as milk, meat and eggs. At sub-therapeutic levels in diets, antibiotics improve growth rate and efficiency of feed utilisation (see Table 1), reduce mortality and morbidity and improve reproductive performance (see Table 2). At high levels (prophylaxis and therapeutic) antibiotics help to prevent disease in exposed animals and to treat diseases (Cromwell, 1999).

Antibiotics used in animals also improve the safety of food as healthy animals result in a safer food supply through the reduction and elimination of certain pathogens. They reduce the cost and improve the quantity of food production through the more efficient use of natural resources which is critical to meet the escalating nutritional and protein needs of a growing world population.

TABLE 1: Effects of anti-microbial agents in the starter, grower and finisher diets on performance of pigsª. Adapted from Cromwell (1999)

Starter Phase (7-25 kg)
Daily gain, kg
Phase (17-49 kg)
Daily gain, kg
Phase (24-89 kg)
Daily gain, kg
Daily feed, kg

ªData from 453, 298 and 443 experiments, involving 13,632, 5,783 and 13,140 pigs for the three phases, respectively.

TABLE 2: Reproductive performance in a swineherd before and after total withdrawal of antibioticsª

Number of litters 398 688
Conception rate, % 91.4 82.6
Pigs born/litter 10.8 10.2
Live pigs born/litter 9.8 9.3
Average birth weight, lb. 2.84 3.04
Pigs weaned per litter (21 days) 8.8 7.5
Average weaning weight, lb. 12.5 11.8
Survival of live pigs to weaning, % 89.7 80.9
Incidence of MMA, %¹ < 10 66

ªCromwell (1999). The data are from a closed, specific-pathogen-free herd at the University of Kentucky. Antibiotics were used in breeding, lactation, starter, grower and finisher diets and for treatment purposes as needed prior to 1972. Antibiotics were discontinued in 1972 and have not since been used as feed additives or as injectables for treatment purposes.

¹Incidence of mastitis, metritis and agalactia (MMA) for the period 1972-1975 only.

As early as the 1960's the use of antibiotics in animal production began to be criticised and this led to regulation of antibiotic use in the United Kingdom (after the Swann Committee) and subsequently in the European Community and elsewhere (McMullin, 2000). The fundamental decision taken by these countries was that active ingredients approved for therapeutic use in human or veterinary medicine would not be approved for non-therapeutic indications. In the 1990's new controversy broke out over the use of these products. According to McMullin (2000), there were a number of technical reasons for this:

  • Resistance to antibiotics used in human medicine is increasing
  • No new class of antibiotic approved for ten years
  • There are more patients in intensive care and suffering immune deficiencies

McMullin (2000) however indicated that the political reasons might be more relevant:

  • Sweden prohibited the use of growth promoters in 1988
  • Sweden and Finland joined the European Union
  • Derogations to continue bans on growth promoters were running out

Various groups were forced to re-examine the perceived danger that the use of antibiotics in animal feeds contributes to a reservoir of drug-resistant enteric bacteria that are capable of transferring their resistance to pathogenic bacteria (salmonella, campylobacter etc.), thereby causing a potential public health risk. Although there remains little scientific evidence to document such transfer, the EU suspended the use of Avoparcin (1997), Tylosin, Virginiamycin, Zinc Bacitracin, Spiramycin, Carbadox and Olaquindox (1999). This leaves only Avilamycin and Flavomycin still approved as antimicrobial growth promoters for poultry. In April 2000, Schering announced that it was halting development of Everninomycin, thus removing pressure for a similar suspension of Avilamycin. These suspensions were effected under the so-called "Precautionary Principle". The EU does, however, recognise that these suspensions cannot be definitive, and are merely a temporary measure pending the analysis of information, particularly risk quantification, collected to establish whether these products may continue to be used safely (McMullin, 1999). There is also a current debate at the federal government levels of the United States about tighter restrictions (Hooge, 1999).

In addition to several widely used anticoccidials in the EU, feed grade pharmaceutical antibiotics remaining on the approved list are monensin, salinomycin, flavophospholipol and avilamycin. None of these drugs, the European Commission believes, is currently important in human medicine and so not an issue concerning the spread of human pathogenic bacterial resistance.

Hooge (1999) hoped that a more scientific approach and a co-operative effort would be used for future rule making on the antibiotic issue in other countries (including South Africa) than has been used in Europe. Some balance has to be achieved so that clinical antibiotic use in human medicine and dietary and therapeutic antibiotic use for gain, feed efficiency and disease prevention and treatment in animal production can continue in the future.

Over the years, several task forces have studied the safety issue of antibiotics and have basically concluded that there is no direct link between antibiotic usage in animals and human health (Cromwell, 1999). The following summary was prepared as a courtesy of Elanco Animal Health (14 June 1999).

The National Research Council

There is no crisis over the use of antibiotics in animals.

"The committee concludes that the use of drugs in the food-animal production industry is not without some problems and concerns but that it does not appear to constitute an immediate public-health concern…….." 1988 report requested by the United States Department of Agriculture and the Centre for Veterinary Medicine.

The HAN Foundation

Antibiotics in animals have not compromised human health.

"Sofar, AGP [antibiotic growth promoter] use did not compromise the human therapeutic use of related antibiotics. Sofar, epidemiological data do not show an increase of infectious diseases as a result of the use of AGP's."
The HAN Foundation (stichting Heidelberg Appeal Nederland) is an independent non-profit alliance of scientists and science supporters, located in the Netherlands.

The "Swedish Experiment" Critiqued by Professor Jaques Viaene

Banning feed-additive antibiotics is counter-productive.

"The Swedish ban of antimicrobials for in feed use without prescription and the Animal Protection Act have lowered production efficiency and increased costs. [p. 4]"
"…the economic burden has been heavy for consumers and for farmers, through increased feed use, loss of production and increased use of therapeutic levels of antibiotics. [p. 4]"
"… in effect, it has been the consumers and the farmers who have paid for the Swedish experiment [p. 19]"
Report by Prof. Jaques Viaene from the Ghent University, Department of Agricultural Economics in January 1997.

The World Health Organisation

Resistance has emerged with little documented impact on humans.

"The use of fluoroquinolones in food animals has led to the emergence of fluoroquinolone-resistant Campylobacter and of Salmonella with reduced susceptibility to fluoroquinolones. There has been little documented impact of this resistance on human health to date, but there is concern about the potential human health consequences if resistance were to increase and spread [p. 8]"
Report by World Health Organisation's Division of Emerging and other Communicable Diseases Surveillance and Control, summarising a meeting on 2-5 June 1998 in Geneva, Switzerland.

On 23 February 1999 the World Veterinary Association (WVA), the International Federation of Agricultural Producers (IFAP), and the World Federation of Animal Health Industry (COMISA) announced a new set of global principles to ensure responsible and prudent use of antibiotics in animals. The three organisations indicated that they are committed to implement the principles in the daily practice so that antibiotics can be used to improve animal health and welfare without sacrificing human health.

Some of the key basic principles for prudent use of antibiotics are:

  • Antibiotics are health management tools which are licensed to enhance good husbandry practice for the purpose of disease prevention, disease treatment and production enhancement. They are a complement to these good husbandry practices and should never be used to compensate for or mask bad farm and veterinary practices.
  • Codes of good practices, quality assurance programs, and education programs should promote the responsible and prudent use of antibiotics.
  • Professional supervision, particularly by veterinarians, and record keeping are essential in the use and control of antibiotic products.
  • Antibiotics used for therapy should be used for as short duration as possible, but for as long as needed and at the appropriate dosage regimen, and attention should be paid to label instructions.
  • Continuous monitoring of the effects (positive and negative) of antibiotics after this use should be conducted in order to adapt the use pattern very promptly.

The principles also recognise that alternatives to antibiotics, provided they are scientifically proven to be efficacious, are needed as an important part of good husbandry practices.


The removal of antibiotic growth promoters from most feeds within the UK has resulted in the search for "natural" and "safe" alternatives (Ratcliff, 2000). For improving poultry performance, for disease prevention and treatment and for reducing feed costs, a variety of commercial products are available for use in combination with or as alternatives to antibiotics (Hooge, 1999).

Alternatives to growth promoters need to be properly evaluated and due consideration given to the quality, safety and efficacy of each product. It is unlikely that a single product will merge as a direct replacement for the registered effect of antibiotic growth promoters. It is more likely that a combination of products may be considered together with a review of the various stress factors that may affect performance and disease, including nutrition, environment and management practices (Ratcliff, 2000).

Feed compounders in the EU are not expecting a quick reversal of the bans, which was scheduled for review at the end of 2000. Rather, they are expanding their use of a wide range of non-pharmaceutical, growth enhancing additives. These additives include organic acids, probiotics, nucleotides, oligosaccharides, enzymes, betaine, mineral growth promoters and 'botanicals' or plant extracts including many traditional herbs and spices. 'Nutraceuticals', 'functional foods' and human homeopathic remedies also are appearing in animal feeds.

Jannie Maritz 0OTK Feeds, PO Box 135, Isando 2123

Cromwell, G.L., 1999. Safety issues, performance benefits of antibiotics for swine examined. Feedstuffs, 7 June 1999, p.18.
Hooge, D.M., 1999. Antibiotics and their alternatives for poultry examined. Feedstuffs, 17 May 1999, p.59.
McMullin, P., 2000. The future of Antimicrobial Growth Promoters: Alternatives for poultry production in the new millennium. International Poultry Production. Volume 8, Number 7, p.30.
Ratcliff, J., 2000. Antibiotic Bans - A European Perspective. Proceedings of the AFMA Symposium on Improving Animal Performance through Nutrition. Pretoria, South Africa, p.128.

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