Antibiotic Misuse & Resistance In Animals

In support of Antibiotic Awareness Day last week, Dr Scott McEwan of the Ontario Veterinary College at the University of Guelph shared a webinar entitled “Antibiotic Use & Resistance in Animals.” During his presentation, Dr. McEwan discussed antibiotic use in animals, the human health impact, and options for intervention. In his webinar, Dr. McEwan pointed out three perceived benefits of antibiotic use in animals:

  • A therapy to cure clinical infections
  • A growth promoter with improved productivity
  • A means to gain higher financial returns

Dr. McEwan concluded that regulatory changes, surveillance programs, and voluntary measures need to be implemented in order to address this global issue. As with humans, diseases found in many animals are treated with antibiotics. Though often effective, these antibiotics frequently leave bacterial strains that are resistant to future treatments.  Animals fed with food containing antibiotics are increasingly carrying antibiotic resistant bacteria[1].

Poultry is becoming more popular in the world as a source of protein; broiler production these days takes only 6 weeks. This is possible because of genetic selection, improved feeding, and health management processes like the use of antibiotics as a method to treat bacterial diseases in the farm atmosphere. As Dr. McEwan pointed out during his webinar, these antibiotics are also used at a sub therapeutic level as growth promoters, allowing farmers to produce larger birds while using less feed – in farming terms, they have improved “the feed conversion”.  The regular and often unnecessary use of these drugs has left strains of bacteria that are now resistant to the effects of antibiotics. The resistant bacteria left behind can replicate about a million fold over a day, becoming a dominant micro-organism in chickens.

Typical Facility for Raising Chicken

The transfer of resistant bacteria from poultry products (and other antibiotic-fed meat sources) to humans can occur through consumption or through handling of contaminated meat. Once a human acquires the pathogen (unfriendly bacteria), it enters into the human intestine and other anatomical sites where it is able to colonize the area[2].  Unfortunately, it seems that we are only at the beginning of understanding how these pathogens may be affecting our health and how they may be linked to serious health conditions.

Scientists have long recognized that pathogens and other bacteria are transmitted from animals to human beings via the food chain. As Dr McEwan mentioned during his webinar, the impact that antibiotic use in animals has on human health is very difficult to measure.  Scientists all over the world agree that the main cause for the spread of antibiotic resistance is the overuse of antibiotics in human and veterinary medicine (including agriculture) [3]. However as Dr. McEwan had acknowledged during his webinar, this is generally not believed to be a problem among veterinarians or farmers. What is the magnitude of antibiotic over usage? Meat producers in the United States feed 25 million pounds of antibiotics to chickens, pigs and cows for non-therapeutic purposes each year. This amount is 70% of all antibiotics produced annually in the United States. The breakdown is as follows: 10 million pounds to healthy hogs, 11 million pounds to poultry and 4 million pounds to cattle. The amount of antibiotics fed to healthy animals is eight times greater than the amount given to sick people[4].

Dr. McEwan suggested the following three interventions to address this global issue:

  • More regulatory changes to improve regulatory oversight & restrictions on antibiotic use
  • More monitoring & surveillance programs such as the Canadian Integrated Program for Antimicrobial Resistance
  • More voluntary measures that introduce prudent use programs & campaigns

The misuse of antibiotics in animals has become a global medical, agricultural and human problem[4]. We endorse the work and efforts of Dr. McEwan and his colleagues at the University of Guelph and look forward to more of his webinars. These are critical in gaining awareness and traction of not just the general consumers, but also policy makers. We believe it is imperative that everyone works together to make inroads into this global health crisis issue.

To learn more about Dr. McEwan’s work, click here!

1. McKellar, Q. (1999). Antibiotics and resistance in farm animals. Nutrition and Food Science. Retrieved September 16, 2010, from

2. Apata, D. (2009). Antibiotic resistance in Poultry. International Journal of Poultry Science 8 (4):404-408.


4.American Society for Microbiology (2007). Resistance Genes In Our Food Supply. ScienceDaily. Retrieved September 16,2010, from

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  1. […] This post was mentioned on Twitter by CDHA, Ondine Bio. Ondine Bio said: The amount of antibiotics fed to healthy animals is eight times greater than the amount given to sick people. […]

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