What are antibiotics? Antibiotics are medicines that are given to people and animals to treat or prevent certain illnesses caused by bacteria. Antibiotics either kill or hinder the growth of harmful bacteria in animals and people.
Why are antibiotics given to cattle? Antibiotics are given to animals that are sick, in order to help relieve the pain and distress due to the illness, help the animal feel better, and recover. Antibiotics may also be given to animals that are in danger of becoming sick in order to prevent the illness or infection from happening in the first place. Just like in people, however, antibiotics do not have any effect on diseases of animals that are caused by viruses or parasites, or other germs besides bacteria. Some antibiotics, for reasons that aren't totally understood, help cattle grow faster and get more out of the feed they eat. These medicines are used at lower concentrations than when they are used to treat illness, and typically are included in the food that cattle eat. The decision whether to use such products for this use (or any other reason) rests with the individual cattle raiser. Not all of them choose to use antibiotics in this manner.
How are antibiotics given to cattle? Antibiotics can be given to animals with injections (shots) under their skin or in a muscle, with pills, by mixing in drinking water, or by mixing in with their feed. Injectable antibiotics are normally used in cattle only when they are sick, or are at high risk for getting sick. Using injectable antibiotics means that the animal has to be held or restrained still enough that the injection can be given in a manner that is safe for the animal and the person giving the injection. This can be an additional stress on an animal, and much more work for the cattle raiser, so its use is reserved for those animals that really need it. Many of the products require a prescription from a veterinarian who is familiar with the animals. People who raise cattle develop relationships with veterinarians and consult with them to determine the best options for disease prevention and treatment. Based on these guidelines, cattle raisers can give the antibiotics to the calves themselves at their farms and ranches. The approval of and directions for the use of these products are dictated by the Food and Drug Administration to guarantee the proper use of these products for animal health and to maintain a safe supply of beef. This includes minimum withdrawal periods that ensure no antibiotic residue remains in the beef we eat. Likewise, giving an animal a pill will require that the animal be restrained as well. A long tube with a plunger is used to place the pill deep in the animal's mouth.
What are some specific examples of the use of injectable antibiotics in cattle? Injecting antibiotics, compared with offering them in animals' feed, results in a higher concentration in the body for a relatively short period of time. Baby calves may need to be treated with antibiotics if they get a case of pneumonia or bacterial diarrhea. Calves that have been recently weaned may need to be treated with antibiotics if they get sick with pneumonia. At any stage of life, calves, cows, and bulls can encounter bacterial infections like pinkeye or infected wounds that require treatment with antibiotics. Examples of commonly used antibiotics for these conditions include penicillin, tetracycline, ceftiofur, florfenicol, tilmicosin, enrofloxacin, and tulathromycin. These treatments are necessary in some cases for the survival of the animal, but also to relieve pain and suffering that these illnesses bring with them.
What are some specific examples of the use of antibiotics in cattle feed? Not all cattle being raised for beef receive antibiotics in their feed. Cattle feeders may choose to mix these medicines in their animals' feed for several reasons.
The period around weaning, or when calves are separated from their mothers, is a time in which antibiotics are used more commonly than other times. The stress of separation, sometimes along with very variable weather conditions can make calves more vulnerable to pneumonia. For that reason, antibiotics may be included in the feed around that time, in order to prevent pneumonia or help mildly ill cattle recover. Since this illness, if it occurs, occurs in the first 2-3 weeks after the stress, these uses of antibiotics are short-term, focused around that time period, and fed in higher concentrations. Common antibiotics for this use include tetracycline and some sulfas: related medicines are used in people, too.
Another use of feed antibiotics may occur when calves are growing rapidly and approaching their final weight. Calves can develop abscesses (pockets of infection) in their livers when a high percentage of their diet consists of grain. In some cases these abscesses can cause illness in the calf. They result in the liver not being fit for food. To prevent this condition, antibiotics such as tylosin are fed to cattle late in the feeding period. Tylosin is not used in humans, although it belongs to a family of antibiotics which are used in people.
What medicines can be used in animal feed is strictly regulated by the Food and Drug Administration. No one, not even a licensed veterinarian, can allow the use of an unapproved medicine, or the use of a higher dose of medicine than is written on the medication label.
Is it better for the animal to get antibiotics in the feed, or by another method? If calves are very sick, they will not eat as much, and would not get enough antibiotic through their feed, so those animals need to be treated individually with injections or another method.
If calves still are eating well, the use of medications in the feed or drinking water is a way a cattle feeder can give medicine to a lot of animals at the same time with no distress to the animal.
Are antibiotics given to cattle the same antibiotics used in people? Regarding forms of antibiotics available for use in cattle feed, the list of human antibiotics in the table of "Commonly Prescribed Antibiotics" in the Merck Manual for Healthcare Professionals shows that two of the 74, neomycin and tetracycline, are available to be used in cattle feed. Tetracycline--or rather its relatives oxytetracycline and chlortetracycline--are used to prevent and treat pneumonia in calves. They are also approved in lower concentrations to help calves grow faster and improve their feed efficiency. Neomycin is a component in a few formulations of cattle antibiotics for growth promotion, but it is rarely used in cattle diets.
Several other common human antibiotics on the list, procaine penicillin, benzathine penicillin, ampicillin, amoxicillin and spectinomycin, are approved for use in cattle are available for use in injectable form. They are not allowed to be mixed in feed. The other antibiotics used for cattle are not on the human list, but some of them are members of drug "families" that include some important human antibiotics. For example, enrofloxacin, an injectable cattle antibiotic, is not used in people, but is closely related to drugs like ciprofloxacin, that is important for people.
Do all cattle need antibiotics in order to stay alive in our current systems of raising cattle? No. As an example, some consumers choose to purchase beef from animals that have never been administered antibiotics. Some ranchers and feedlots raise cattle in a manner that targets this market, which is often referred to as the "natural"beef market.
In most herds, at least a few of the animals have needed an antibiotic treatment at some point in their life, or have needed feed grade antibiotics to prevent a case of illness. Responsible ranchers and feeders, even those producing beef for a "natural" market, give sick animals antibiotics when it's necessary for the animal's well-being (these treated animals are then removed from the group of animals that are marketed as "natural") Vaccine programs, which prevent diseases, and management steps like keeping a closed herd (not buying new animals from outside the herd) are among the many tools used by many cattle raisers to keep animals healthy and avoid the need for antibiotics.
How do antibiotics affect the meat from an animal that is treated with them? Most antibiotics given to animals end up being absorbed into their bloodstream, but some that are given orally (through the mouth) just have their action in the intestines and never enter the bloodstream. The antibiotic that is given to an animal is "metabolized," or changed by the chemistry of the body, to forms that may be more effective against the bacteria, more readily distributed through the body, or more easily removed from the body. This metabolism is different for every different antibiotic and for each different route of administration, but its end result is the eventual elimination from the body.
People giving antibiotics to food animals are required to follow a "withdrawal time" after treatment. The withdrawal time is a waiting period after treatment that gives the animal time to reduce the concentration of the drug in its body, and therefore in the meat (or milk or eggs) the animal produces. This withdrawal time is different for each antibiotic, and is set by the Food and Drug Administration. It reflects the point in time at which the antibiotic is at a low enough level in the animal to not result in safety problems for people eating its products.
The US Department of Agriculture's Food Safety Inspection Service (FSIS) tests for the presence of antibiotics in the carcasses of animals used for meat. Not every animal is tested, however. Carcasses are tested at random, along with "targeted" sampling of carcasses from farms that have had problems in the past. Fines and prison time are possible for people selling animals with levels of antibiotics over the limit. The numbers of violations are extremely low, and are published regularly on the FSIS website.