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Feed additives in beef farming

We already talked about how beef farmers use antibiotics to keep their animals healthy. In cattle, almost all antibiotics need to be given by an injection because the rumen microbes (bacteria and protozoa) will break down most of the antibiotics we use in animals. There are a few exceptions, however.

One type of antibiotic that is used commonly in beef farming (and in other cattle farming, too) are ionophores. These medications act directly on the rumen microbes. They change the way the ions (like sodium and chloride) can pass across the cell walls of the microbes, limit the microbes’ growth and reproduction (they are considered coccidiostats), and change the way they use nutrients.

Ionophores are not approved for use in people, and can be very dangerous to animals that are not ruminants. (For example, ionophores can be deadly to horses if they are accidentally given cattle feed that has this medication added.)

Ionophores are used as feed additives on many beef farms. They are helpful in a few different ways. First, they decrease the incidence of disease caused by coccidia. While all cattle (and all ruminants) have “good” microbes in their rumen, there are also “bad” microbes that can cause disease. These “bad” microbes can cause very severe diarrhea that can quickly result in death. By using ionophores as a feed additive, farmers are using these medications as prophylaxis to prevent diarrhea from coccidial diseases.

In addition to keeping the bad coccidia at bay, ionophores also help to keep some of the bad bacteria under control. Ionophores are more specifically active against some types of gram-positive bacteria. These bacteria can cause intestinal disease like bloat in cattle, so prophylactic use of ionophores in feed helps keep populations of these bacteria low and decreases the incidence of some intestinal diseases.

Another way ionophores are helpful is in increasing feed efficiency of cattle. By altering the way the “good” microbes use ions, these medications also alter the way the microbes use nutrients. Remember that the rumen microbes digest the fiber and protein in the cattle’s feed, and then the cattle digest the microbes as their protein source. Ionophores make the rumen microbes less efficient at digesting protein, so there is more available for the cattle to digest. So now the cattle get a double-dose of protein – some of the protein from their feed, and all of the protein from the microbes.

Ionophores don’t completely stop the rumen microbes from digesting protein, but they do change the end products of protein digestion. The same end products are made (different types of fatty acids), but in slightly different ratios. The cattle can’t use all the fatty acids the microbes make in the same way, and ionophores change the ratio in favor of the types of fatty acids that cattle can use for nutrition more efficiently.

And, believe it or not, all these benefits can be accomplished with a very small amount of medication. These medications are mixed with the cattle’s main grain feed at a ratio of 5-40 grams of medication per ton of feed. That’s 0.011-0.088 pounds of medication in 2000 pounds of feed. That’s a big benefit from a very tiny amount of medication!

All the benefits cattle see from the use of ionophores in feed result in healthier cattle that grow better with the same amount of feed. This results in a cost-savings for the farmer (in veterinary care for the animals and in feed costs), and these savings help keep the cost of meat down at the grocery store.

Antibiotics in beef farming

So now that we know what antibiotics actually are, how are they used in beef farming?

When most people think of antibiotics, they think about pills or capsules. In small animal veterinary medicine, we do often use antibiotics in the form of pills, capsules, or chewable tablets.

But in cattle things are a little different. Remember those rumen protozoa? Well, they do some funny things to antibiotics, and we can’t use these drugs (or most drugs, for that matter) in an oral form in cattle. So they have to get injections.

Sometimes we use antibiotics that are also approved for use in people, like Baytril. More often, we use antibiotics that are not approved for use in people, like Micotil and Resflor. In fact, if Micotil is accidentally given to a person it can kill them by causing a heart attack and Resflor may have side effects of bone marrow suppression in people.

Because some antibiotics that are approved for use in animals may have side effects in people, it is essential that farmers keep good records of which animals they use antibiotics in, what date the antibiotic was given, and how much antibiotic was given. The farmers then need to be aware of the withdrawal date and not sell the animal for food before that date. At the processing facility, meat can be randomly tested for antibiotic residue, or the inspecting veterinarian can request testing on the meat from an animal they have reason to think might have antibiotic residue.

If meat from an animal is found to have antibiotic residue, all the meat from that animal is condemned (discarded). The farmer who owned that animal will be subject to citations from the FDA, and may see other consequences such as jail time and not being able to sell any animals for food for people. (This can be devastating for a farmer’s business.)

So why do we use antibiotics in beef cattle in the first place? First and foremost, we use antibiotics to treat disease. Just like people, cattle can get bacterial infections that require antibiotics to treat them.

Antibiotics are also commonly used for prophylaxis, or prevention of disease. In many feedlots, cattle are brought in from many different farms in different areas of the country. Some of these cattle have been shipped in a trailer for many hours. The stress of travel and meeting lots of new cattle all at once can lower their resistance to disease and make them more susceptible to infections, especially pneumonia. When new calves enter a feedlot, most farmers will vaccinate them for the most common respiratory diseases. The problem is that vaccines take up to two weeks to be effective. And in the meantime, the cattle may be exposed to many different bacteria.

Often, when the calves get their vaccines when they arrive at the feedlot, they also get a single dose of a long-acting antibiotic. Remember the hormone implants that release hormone into the animal’s body over a period of time? Long-acting antibiotics are similar, except the antibiotics are in a liquid form and are only released for 2-14 days (depending on the medication). This single dose of antibiotic helps keep many cattle from getting sick, and needing even more medications.

Some antibiotics can also be used as feed additives. I know, I just said that we can’t use antibiotics orally in cattle because of their rumen protozoa. The medications we can use orally actuallyhave a primary effect on those protozoa, and a secondary effect on the cattle. We’ll talk about them next time.

What is an antibiotic?

We’ve all heard about antibiotics, and chances are good that we’ve all taken them at some time or another. But what are they, exactly?

The word “antibiotic” is commonly used to describe medications that kill bacteria, fungi, or protozoa. Technically, this is incorrect. “Antimicrobials” are drugs that kill bacteria, fungi, protozoa, or viruses. Antibiotics only kill bacteria. (Antifungals kill fungi; antiprotozoals kill protozoa; antivirals kill viruses.) Doctors and veterinarians frequently use “antibiotics” and “antimicrobials” interchangeably. For the purposes of this article, I’m mostly going to use the word antibiotic to talk about all these kinds of medications.