Cattle Today

Cattle Today

cattle today (10630 bytes)

by: Stephen B. Blezinger

Over the years the cattle industry has developed quite a number of feed additives which have proven very useful in improving animal health and performance. These additives are active in a number of areas in the animal reduction of microbial related diseases, improved feed efficiency and gains, estrus suppression, control of bloat and coccidiosis. When properly used in a well-managed environment, many of these additives can improve performance and profitability substantially. They cannot, however, take the place of good management. Unfortunately, under many circumstances, many additives will be used as a “band-aid” to attempt to cover poor management practices. In situations such as these, the cost of the additive is exactly that, a cost to the program and not an investment as many are designed to be, producing a positive return. In many situations, cattlemen have become frustrated with the apparent lack of response after they have spent added dollars on one or more additives. They often come away from the situation with a bad taste in their mouth and a poor perception of a given product. This perception is often not deserved because circumstances were not appropriate for the product to work as it was designed. Therefore it is important to understand what the various additives can and cannot do.

One of the most important groups of additives available to the cattle producer is that known as ionophores. The name ionophore is the technical name for a class of additives commonly fed to cattle to improve feed efficiency and rate of gain. Trade names for the most common products in this class include Rumensin®, Bovatec® and Cattlyst®. Ionophores are added to feeds or supplements and are designed to effect the microbial population found in the rumen. In their most basic form, ionophores can be classified as antibiotics, having a detrimental effect on certain types of bacterial in the rumen. Although research has shown that some of this compound may, in fact, be absorbed by the animal, none is actually incorporated into the muscle or fat tissues of the animal.

Let's take a specific look at the ionophores in an effort to understand their function and the differences in the three products available to the producer.

Some Basics

The predominant effect of ionophores is, as mentioned, on rumen bacteria. An ionophore such as Rumensin®, when fed to a ruminant will select against certain types of bacteria. These microbes tend to be those that reduce the efficiency by which a beef animal utilizes energy. These types of bacteria will take nutrients from feed, utilize certain components and release other non-usable or detrimental by-products. Some of these by-products can include methane gas, carbon dioxide, lactic acid and heat. These are all basically wastes of energy found in feeds. When we feed an ionophore, they act as an antibiotic or anti-bacterial agent on many of these types of bacteria. This results in a shift in the bacterial population to a higher concentration of “beneficial” bacterial or those which consume nutrients and produce helpful by-products in the rumen. These helpful by products include bacterial protein and organic acids which can be used to make energy sources in the animal's body. When this process takes place, the remaining bacterial population becomes more efficient, thus requiring less feed to provide the same or more energy to the animal. Often, this will actually result in a decrease in intake. This occurs since energy intake effects actual dry matter intake. When more energy becomes available, overall intake will tend to drop. Other theories regarding this intake reduction are that ionophores tend to be unpalatable but since they are fed in such a small amount this may be questionable.

Ionophores are fed extensively in the feedyard industry. Virtually every feedlot animal will receive one of the above mentioned ionophores during the finishing phase although it is also common in the grazing phases as well. Use of ionophores has become more common in breeding cattle as well. This is true not only in growing and developing bulls and heifers but also in mature cows to improve energy efficiency. In situations such as these it is important to note that an ionophore should only be used in a situation where good quality forages are available. If fed with a poor forage where nutrient intake is already a problem, feeding an ionophore which may depress intake will only compound this problem.

Interestingly, like most additives, ionophores are typically fed in very small amounts. The actual amount fed will depend on the product and the application. The following table outlines normal feeding ranges for each product and the range of inclusion into finished rations.

Table 1. Ionophore Feeding and Inclusion Rate Guidelines

Feeding Rate/hd/day, mg
50 to 360
60 to 360
30 to 150

Inclusion Rate, gms/ton
5 to 30
10 to 30
5 to 10


As noted, the level of ionophore added must be correlated with actual feed intake in order to optimize the dose of product delivered into the animal. Specific guidelines have been established by the Food and Drug Administration (FDA) for the use of this additive and many others and the combinations in which it can be fed with other additives.

Benefits and Considerations

The approved ionophores (plus a number of others that have not been approved to date) have shown a number of benefits. As mentioned before, the use of ionophores is standard procedure in beef finishing diets. Rumensin®, Cattlyst® and Bovatec® are all indicated for improving feed efficiency in feedlot animals. Cattlyst® and Bovatec® are indicated for increasing the rate of weight gain. Other possible advantages of ionophores include:

•      Decreased incidence of acidosis

•      Decreased incidence of feedlot bloat

•      More efficient utilization of protein

•      Control/prevention of coccidiosis

Why These Products Work

To be very specific, ionophores are named as they are because of their effect on ion flow across cell membranes. This effect is more pronounced against gram positive bacteria and against hydrogen producing bacteria. The overall effect is to modify rumen fermentation in favor of the more efficient propionate (propionic acid) production and away from the less efficient acetate (acetic acid) and butyrate (butyric acid) production.

Feed Efficiency: The increased efficiency of rumen fermentation which occurs by the feeding of ionophores allows the cattle to capture more energy from feedstuffs. Feedlot cattle consume feed until an internal, chemically-based, physiological signal alerts the brain that the animals' energy requirements are satisfied. Less feed is required to elicit this signal when ionophores are fed, therefore, cattle fed ionophores tend to eat less feed but maintain the same rate of gain. Utilizing less feed to achieve the same gain results in more favorable feed efficiency. Feed efficiency is a major determinant of feedlot profitability.

Decreased Acidosis and Bloat: Feedlot finishing diets are high in grain and low in fiber. These conditions favor rumen acidity and the potential for feedlot bloat. Ionophores reduce the production of lactic acid in the rumen controlling acidity and reducing the incidence and severity of bloat.

Coccidiosis Control: Rumensin and Bovatec both are effective in controlling coccidiosis when fed at appropriate levels. Rumensin is also approved for the prevention of coccidiosis. In many situations the amount of Rumensin and Bovatec needed for maximum coccidiosis control is higher than that which would normally be fed for improved feed efficiency. Bovatec needs to be fed at 1 milligram per kilogram of body weight (0.45 milligrams per pound of body weight) for coccidiosis control. Rumensin needs to be fed at 0.14 to 0.42 milligrams per pound of body weight for coccidiosis control depending on the level of exposure. Cattlyst is not effective in controlling coccidiosis.

Comparing the Products

Rumensin is by far the most commonly used ionophore included in feedlot diets. It is effective in improving feed efficiency, coccidiosis control and prevention, and at reducing the incidence and severity of bloat. Rumensin is also approved in combination with MGA and/or Tylan. For optimum effectiveness it should be fed at the top end of the range shown in Table 1. Rumensin is a good ionophore choice for most feedlot situations.

Bovatec's spectrum of effectiveness in feedlot situations is similar to that of Rumensin but the potency on a milligram to milligram basis is believed less than the potency of Rumensin. Bovatec is mainly used in young cattle and some feedlot grower diets. Bovatec may be useful in situations where bunk management is less than ideal and daily intake of feed and the ionophore are not constant. Bovatec can be used in combination with Oxytetracycline, MGA and Tylan. As with Rumensin, in order to achieve optimum effectiveness in a feedlot, Bovatec should be fed near the top of the range shown in Table 1.

Cattlyst is the newest of the ionophore medications. It has a clearance for not only improved feed efficiency but also increased rate of weight gain in feedlot cattle. It is gaining some acceptance in feedlots especially those that feed exceptionally high grain diets and have excellent bunk management. Cattlyst does not tend to decrease feed intake as much as Rumensin and Bovatec. There are some considerations to the use of this product, however. Cattlyst is not effective at controlling coccidiosis. No combinations of Cattlyst and other medications are approved. The Cattlyst molecule is not as stable as Rumensin and Bovatec, therefore, products manufactured with Cattlyst have an expiration date. Supplements manufactured with Cattlyst expire 6 weeks following the date of manufacture. Complete feeds expire 2 weeks following manufacture. These expiration dates make Cattlyst containing feed distribution difficult. Optimal finishing diet inclusion rates will be near the top of the range shown in Table 1. Cattlyst is an effective product and may be considered when: 1) the expiration date of the feed is not a concern, 2) coccidiosis is not a concern and, 3) there is no need for another medication such as MGA, Tylan or oxytetracycline.


Ionophores have consistently proven to be an asset in growing and finishing operations and are well accepted as a means to increase the profitability of most cattle operations. All three products have been shown effective and have advantages in certain circumstances. It is important to evaluate the feeding situation, the level of management and what is to be accomplished prior to the selection of an ionophore.


Send mail to with questions or comments about this web site.
Copyright © 1998-2002 CATTLE TODAY, INC.