by: Stephen B. Blezinger
Ph.D., PAS

Part 1

Livestock producers have fed antibiotics to promote growth to food animals for years. Over recent years, scientists have raised concerns that, in conjunction with the excessive use of antibiotics in humans, the use of sub-therapeutic levels of antibiotics in food animals could lead to serious health risks for people. Should this supposition and a consumer base buying into the theory ban the use of such drugs, a significant reduction would be seen in production efficiency, driving up the cost of meat. Some in the industry believe that the scientific evidence linking low-dose usage of antibiotics to drug-resistant illnesses in people is too inconclusive and does not justify banning their use.

We are going to look at both sides of this controversy. First from the side of the coin that sees the need to eliminate the use of antibiotics. Then we'll examine the cattle industry's view of this issue. As you will see, finding common ground will be very difficult.

From the Advocates of Banning Antibiotic Use

In most cases these folks see that producers have been feeding antibiotics to the animals we eat for decades it was found that small doses of antibiotics administered daily would make most animals gain several percent more weight than they otherwise would on a daily basis.

They believe that it is not completely clear why feeding small "sub-therapeutic" doses of antibiotics, like tetracycline, monensin, lasalocid, to cattle helps them gain weight or gain weight more efficiently. In most cases they do not see that this mode of action takes place for them most part in the rumen and that it is largely linked to causing shifts in the microbial population in the rumen resulting in higher concentrations of those microbes that produce nutritional products that animal uses for energy, protein, etc. The level of antibiotic which actually leave the digestive tract and enter the circulatory system is very small.

This group attempts to make the point that the meat industry doesn't publicize its use of antibiotics, so accurate information on the amount of antibiotics given to food animals is hard to come by. By their numbers it is estimated that 15-17 million pounds of antibiotics are used sub-therapeutically in the United States each year. This group contends that antibiotics are given to animals for therapeutic reasons, but that use isn't as controversial because few argue that sick animals should not be treated.

The anti-antibiotic crowd believes that the biggest controversy centers around taking antibiotics that are used to treat human illnesses and administering them to food animals. It is believed by many in this group that there is an increasing amount of evidence suggesting that sub-therapeutic use of antibiotics in food animals can pose a health risk to humans. If a group of animals is treated with a certain antibiotic over time, the bacteria living in those animals will become resistant to that drug. Comments by microbiologist Dr. Glenn Morris, indicate the view that the problem for humans is that if a person ingests the resistant bacteria via improperly cooked meat and becomes ill, he or she may not respond to antibiotic treatment.

Concern about a perceived growing level of drug-resistant bacteria has led to the banning of sub-therapeutic use of antibiotics in meat animals in the European Union and other parts of the world. The World Health Organization (WHO) is concerned enough about antibiotic resistance to suggest significantly curbing the use of antibiotics in food animals. In a recent report, the WHO announced its intention to "reduce the overuse and misuse of antimicrobials in food animals for the protection of human health." Specifically, the WHO recommended that prescriptions be required for all antibiotics used to treat sick food animals, and urged efforts to "terminate or rapidly phase out antimicrobials for growth promotion if they are used for human treatment." This would reduce the use of antibiotics for the purpose of increasing feed efficiency or improving gain and would potentially result in the requirement that antibiotics delivered via feed require a prescription, thus requiring the participation of veterinarians in the feed industry.

Even though it has been reported that conclusive evidence directly linking the use of drugs in food animals to an increase in drug-resistant bacteria that make people sick has not been uncovered, a number of recent studies suggesting such a link concern many scientists. The position is held that there is no evidence that antibiotic resistance is not a problem, but there is insufficient evidence as to how big a problem it is. In other words, while no significant evidence exists that proves this is a problem, a supposition DOES exist by a portion of the scientific community and therefore it is a problem.

For instance, one study published in the New England Journal of Medicine (Feb 6, 2002) researchers found links that strongly suggested that the people who developed Cipro-resistant bacteria had acquired them by eating pork that were contaminated with salmonella. The report concluded that salmonella resistant to the antibiotic flouroquine can be spread from swine to humans, and, therefore, the use of flouroquinolones in food animals should be prohibited.

Another New England Journal of Medicine study (Oct 18, 2001), found that 20 percent of ground meat obtained in supermarkets contained salmonella. Of that 20 percent that was contaminated with salmonella, 84 percent was resistant to at least one form of antibiotic.

In a specific example, some, including the FDA, believe the overuse of Baytril, an antibiotic used to treat a variety of infections in numerous species, led to an increase in treatment-resistant bacterial infections in humans. Baytril is used by poultry growers to protect chickens and turkeys from E. coli. The size of commercial chicken flocks precludes testing and treating individual birds, so when a veterinarian diagnoses one infected bird, farmers treat the whole flock by adding the drug to its drinking water. General use of Baytril, therefore, falls in the gray area between therapeutic and sub-therapeutic.

A reported problem with this is that Baytril is the sister drug to Cipro, which is used to treat and prevent anthrax as well as campylobacteriosis and salmonellosis in people. The Food and Drug Administration, doctors, and consumer groups, have all urged that Baytril be removed from the market on the grounds that its use in animals may eventually compromise the power of Cipro and similar antibiotics to fight disease in humans. Cipro and Baytril belong to a class of drugs known as fluoroquinolone, among the most powerful antibiotics currently available.

When the FDA proposed pulling Baytril use in chickens a year ago due to sharp increases in resistance to fluoroquinolones in campylobacter bacteria, one of the two manufacturers voluntarily withdrew its product.

Bayer officials continue to offer the human drug Cipro at reduced rates to the American public, saying that they are not convinced that the use of fluoroquinolones in animals can be blamed for increased resistance in people. Until more proof is found of the specific danger to humans, they will not withdraw their product from the chicken market.

This group believes the meat-production industry contends that there is not enough conclusive evidence to support measures like the FDA's proposed ban against flouroquinolones. Although none deny that the spread of antibacterial resistance is a real problem, proponents of sub-therapeutic antibiotic use in animals point out that the problem stems from overuse of all antibiotics, including therapeutic and preventative use in both animals and humans. Agricultural use may contribute to the problem, but it is impossible to determine to what extent.

Interestingly the WHO blamed the worldwide upswing in resistance to antibiotics on a combination of factors that included "overuse in many parts of the world, particularly for minor infections," and "misuse due to lack of access to appropriate treatment." The factors involved in the problem are clearly not limited to antibiotic use in animal feed.

"When someone's sick and goes to the doctor, they still expect to get a prescription," said National Chicken Council spokesman Richard Lobb. He said that people, in many cases, should look to themselves for the causes of antibiotic resistance, referring to the American practice of prescribing antibiotics for even the most minor of illnesses.

Increased use in hospitals may also contribute to the resistance problem. "Today, especially in intensive care wards, the amount of antibiotics in the environment can become high enough that people in the vicinity of patients receiving antibiotics are exposed continuously to low levels of antibiotics," microbiologist Abigail Salvers of University of Illinois commented in Scientific American. The contention here is that this low level of exposure, is one reason why highly resistant bacteria are developing in hospitals. She went on to propose that a similar phenomenon may be taking place in agriculture.

According to Alexander S. Matthews, president and CEO of the Animal Health Institute (AHI), removal of antibiotics from animals' feed and water "would lead to increased animal disease, a reduction in food safety and gain little, if anything, in the effort to control resistance." He suggests developing "prudent use principles."

Lowering or halting sub-therapeutic antibiotic use in animal production could have serious economic effects on the meat and poultry industry. According to a report released in May 2001 by USDA's Economic Research Service, discontinuing the use of antimicrobial drugs in hog production would initially decrease feed efficiency, raise food costs, reduce production and raise prices to consumers. According to the same report, U.S. hog producers saved about $63 million in feed costs in 1999 due to their use of low levels of sub-therapeutic drugs; they would have suffered an estimated loss of $45.5 million in 1999 if the drug use was banned.

Related to the pressure being brought, there is a growing movement to reduce at least the sub-therapeutic use of antibiotics in animals raised for food. Tyson Foods, Perdue Farms and Foster Farms, which collectively produce a third of the chicken Americans eat, declared their intention to greatly reduce the amount of antibiotics fed to healthy chicken. There is still no way for consumers to know whether one of these companies' chickens has been treated with antibiotics, although some corporate consumers, McDonald's, Wendy's and Popeye's among them, are reported to refuse to buy chicken that has been treated with fluoroquinolones. Increased public pressure may cause the companies who grow animals for food to collectively decide that putting extra weight on feed animals isn't worth the possibility that they are putting consumers' health at risk.


As mentioned, this article discussed in fairly mild form, some of the beliefs held by those who feel all antibiotic use should be eliminated in the food animal industries including cattle. As noted, many of their positions are based on very weak research and extrapolation. In the next issue we will examine the cattle industry's side of this controversy and hopefully shed some common-sense light on the topic.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached at 667 County Road 4711, Sulphur Springs, TX 75482, by phone at (903) 352-3475 or by e-mail at [email protected]. For more information you can also visit


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