Current Progressive Cattle digital edition

Ionophores: Same technology, different times

Kim Mullenix for Progressive Cattleman Published on 24 May 2017
Place mineral supplements where grazing cattle visit often

An ionophore is a feed additive used in beef cattle rations to improve feed efficiency and animal gains. Ionophores improve fermentation characteristics in the rumen, which lead to improved production efficiency.

These additives are also known for their ability to help with the control of bloat, coccidiosis and acidosis. The primary forms of ionophores used for beef cattle on pasture include monensin and lasalocid.

Ionophores select against gram-positive bacteria and protozoa in the rumen. When these bacteria are controlled, the rumen fermentation environment becomes more efficient because fewer waste products, such as methane, are produced.

This also creates a favorable environment for more desirable bacteria to grow that produce fermentation products which can improve the overall energy status of the animal, resulting in greater feed efficiency.

The use of ionophores can be beneficial for grazing animals. Although a large portion of the research conducted with ionophores has been done with cattle in feedlots, there is an increasing use in the pasture side of the production chain.

A review of grazing trials where steers or heifers were supplemented with 155 milligrams per day of monensin reported an improvement in average daily gain of 0.18 pound per day (a 13 percent increase compared to cattle that were not supplemented).

On medium- to high-quality pasture, cows have been observed to have increased weight gain, feed efficiency and maintain greater body condition scores compared to non-supplemented cattle.

Different times

While the benefits of this technology are well-known, changing times in the cattle industry make us rethink how supplementation with an ionophore can help us move forward in different times. So how can we – with lower prices and a more aware public perception – use this technology to benefit the industry? The following provide some insights:

Inclusion in more products for grazing cattle

Most often, ionophores are added into dry or liquid commercially manufactured feeds or in mineral mixtures. Ionophores are included in small amounts when mixed into commercially formulated feeds. Consistent intake is needed for animal responses to be observed.

Sometimes delivering these products to grazing cattle can be challenging. If a supplement is used, it must be fed on a daily basis to provide consistent consumption. Loose minerals in a feeder or blocks placed in areas where grazing cattle visit often can help keep intake on track. These would be near the watering system or in shaded areas.

A grazing study in Nebraska evaluated using a block-type supplement containing an ionophore for grazing cattle. Average consumption of blocks containing ionophores was 1.4 ounces per head per day.

Cattle gained 5 percent more when provided blocks containing ionophores; however, this was not statistically different than blocks without the ionophores. The availability of these products is increasing across the U.S., making supplementation of grazing cattle with ionophores more feasible from a logistical and economic standpoint.

Environmental benefits

There is increasing scrutiny of the beef industry regarding the contribution of ammonia and methane production from ruminants. Excess methane and nitrous oxide emissions are considered sources of greenhouse gases. A research trial by Cornell University quantified the benefits of ionophores in decreasing ammonia and methane emissions to the environment.

Data from the experiment suggests across either pasture or feedlot systems, the use of ionophores may decrease protein degradation in the rumen and increase feed protein utilization by 3.5 percent.

The authors noted ionophores may reduce methane production by as much as 25 percent and feed intake by 4 percent without a decrease in animal performance. These data illustrate ionophores are a useful part of a sustainable beef production system model.

Stacking technologies

Practices like the use of ionophores and implants are well established, but we often don’t think about the potential benefits of using these in a systems approach. It may be a practice already done in concert with other technologies in the operation, but what is the real benefit of adding these together?

In 2012, the Noble Foundation conducted an 84-day grazing trial with steers on cereal rye. Implanted steers fed a mineral containing an ionophore had a greater average daily gain (about 2.5 pounds per head per day) compared to those not implanted and fed salt (about 2.1 pounds per head per day), illustrating the potential to use these technologies simultaneously.

Government regulation – Where do ionophores fit?

All antimicrobials administered through livestock feed require Veterinary Feed Directives (VFDs) through the FDA. A VFD is like a prescription written by a veterinarian for administering feed-through antimicrobials. However, only antimicrobial drugs medically important for treating human disease that were previously approved for production purposes are impacted.

Examples of drugs affected include but are not limited to: neomycin, tylosin, virginiamycin, chlortetracycline and oxytetracycline. It is important to note ionophores such as lasalocid and monensin do not require a VFD unless used in combination with a medically important antimicrobial.


As the beef industry continues to evolve and move forward, understanding how research-proven technologies can be used in new ways to improve production are important. What was once considered an “optional” technology like ionophores is now one that should be on our checklist of items commonplace in the operation.

Rather than thinking about this as the same technology, ask yourself how it can be used as part of a systems approach to beef production.  end mark

PHOTO: If mineral supplements are used, place them in an area where grazing cattle visit often. This would be near the watering system or in shaded areas. Staff photo.

Kim Mullenix
  • Kim Mullenix

  • Assistant Professor - Extension Specialist of Beef Cattle Management Systems
  • Auburn University
  • Email Kim Mullenix