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.