Lindsay Chichester – UNL Extension Educator and Dr. Dee Griffin - Feedlot Production Management Veterinarian and Professor at Great Plains Veterinary and Educational Center
Many people are concerned about antibiotic resistance. What is antibiotic resistance? Antibiotic resistance occurs when an antibiotic loses its ability to effectively control or kill certain bacterial growth. Why is this concerning? The bacteria become “resistant” to an antibiotic and will multiply. The next time illness occurs (in human or animal); it may take a different antibiotic or a stronger dose of an antibiotic to control the bacterial infection.
Whenever antibiotics are needed and used, whether for livestock or humans, they need to be administered judiciously with great responsibility. In many cases, when an animal becomes ill enough to need an antibiotic, it is a matter of life and death for that animal. If the animal does not receive the antibiotic it will suffer and may die. So it is the responsibility of the livestock producer to ensure an animal receives a quick diagnosis and the proper treatment.
South Dakota State University Extension put together a nice antibiotic fact sheet (http://www.sdstate.edu/vs/extension/beef-procedures-antibiotics.cfm). Antibiotics are given to people and animals to treat or prevent illnesses caused by bacteria. Antibiotics are given to livestock to relieve the pain and/or distress from the illness, to make them feel better, and recover. Just like with people, antibiotics have no effect on diseases caused by viruses or parasites. Antibiotics can be administered several ways, including an injection under the skin, via a pill (bolus), or mixed in the feed or water. When an animal is very sick an injectable antibiotic is the quickest route to get the animal on the road to recovery. It should also be mentioned that if animals are sick, they don’t feel like eating or drinking, so mixing an antibiotic into the feed or water is not always effective. All livestock antibiotics approved by the FDA (Food and Drug Administration) since 1988 require a prescription from a veterinarian who has developed a relationship with the livestock producer and can help determine the best options for disease prevention and treatment.
A common myth is that antibiotics are mixed into ALL livestock rations. That is untrue. There are certain times in an animal’s life when things are more stressful, and antibiotics in the feed can make good sense. For example, if animals are co-mingled at a young age they are more likely to transmit bacteria back and forth (just like kids at daycare or in a school classroom). It is hard on their bodies, and being sick can take a toll on their health and make recovery harder. Also, weaning is a stressful time on animals. High levels of stress often result in a weakened and susceptible immune system which increases the probability of bacterial infections. Weather conditions may also take a toll on livestock. Extreme fluctuations in temperature and the inability to get dry or warm can result in illness or pneumonia. Finally, as an animal approaches its final weight, antibiotics may be fed to help prevent liver abscesses, which may be caused from a high ration of grain in the diet.
The use of antibiotics in feed or water is at the discretion of the livestock producers, their veterinarians, and nutritionists. Some beef producers do not feed antibiotics during these times of stress, and will just treat animals that may get sick, and some may treat all the animals to keep them all healthy. Also, animals that are fed for a niche market (i.e. organic, naturally raised, or no antibiotics used systems) will not have received an antibiotic (in these programs if they receive an antibiotic, then they are completely removed from the program). Geographically, there are some locations in the U.S. (Midwest – Iowa and Eastern Nebraska, South Texas, and Desert Southwest – Arizona and California) that feed fewer antibiotics in the feed because of a diet higher in roughages and fewer fluctuations in weather. There is no right or wrong method; each beef producer weighs the advantages and disadvantages of the cost (antibiotics are expensive to manufacture and purchase), labor, time, efficiency, withdrawal period, and animal’s health to make a decision that is best. Animals from some backgrounds can handle stress better than others and may never get sick, while others may get sick multiple times.
A withdrawal date or time is the amount of time that must pass after an animal has received an antibiotic to the time when that animal or the products it produces can be consumed. This is measured in days, and is taken very seriously by persons involved in food production. A withdrawal date or time will vary depending on the medication; these dates are set by the FDA. The livestock industry has programs in place by species (beef, swine, sheep, dairy, etc.) for livestock producers designed to enhance and reinforce proper animal care practices, recordkeeping, and the responsible and judicious use of antibiotics.
When would antibiotics be included in the feed?
Liver abscesses can be associated with grain intake and consumption. These high energy diets require intense feeding management and can be associated with acidosis. A liver abscess can be caused when cattle have an episode of acidosis. Acidosis is the most common nutritional disorder in the feedlot and can occur when cattle are fed a high amount of grain in a short time, or when cattle overeat (regardless of the feedstuff). This results in the production of more lactic acid than can be buffered by the rumen and water from the circulatory system is drawn into the rumen, resulting in a change in pH. Dr. Dee Griffin, DVM, says there are many reasons cattle overeat, but one of the more common reasons is a decrease in barometric pressure. Cattle can sense a storm coming and will eat more than usual. If that diet is high in energy (i.e. grain) it may result in an acidosis event. Dr. Griffin says that when the pH in the rumen falls below five, certain bacteria can cross the rumen into the liver resulting in a liver abscess. To help control the abscesses, an antibiotic called Tylan can be fed to cattle in their feed. Dr. Griffin and feedlot nutritionists estimate that at least 75% of cattle in feedlots are fed Tylan. Tylan helps reduce liver abscesses by 40-70%. As mentioned above, this is an individual beef producer’s decision.
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