by: Kim Mullenix, Ph.D.
Extension Beef Cattle Specialist and Soren Rodning, DVM, Extension Veterinarian

What is an ionophore?

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 leads 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, lasalocid, and laidomycin propionate. Trade names of these ionophores include Rumensin, Bovatec, and Cattlyst.

How do ionophores work and what are the potential benefits?

Ionophores are designed to effect the microbial population in the rumen (where a fermentation of forages and feed occur in the digestive tract of beef cattle). An ionophore is used to select against gram-positive bacteria and protozoa in the rumen. These microbes tend to reduce how effectively beef cattle use energy. When these bacteria are controlled, the rumen fermentation environment becomes more efficient because less waste products, such as methane, are produced. This also creates a favorable environment for more desirable rumen bacteria to grow and flourish. These bacteria digest forage and feed resources and produce fermentation products that can improve the overall energy status of the animal, resulting in greater feed efficiency. When the remaining population becomes more efficient, this allows less feed to be used to provide the same or more energy to the animal.

Other potential benefits of ionophores:

•Coccidiosis Control -Because ionophores select against certain bacteria, they can be effective in helping to control coccidiosis. Rumensin and Bovatec (for cattle up to 800 lb) are labeled for control of coccidiosis.

• Reduce the incidence of bloat in feedlot cattle or cattle on primarily grain-based diets.

How can they be fed?

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. In order for ionophores to be effective, they must be delivered through the feed on a consistent basis. Thus, feed products that are fed daily or meant for regular intake every day (such as most mineral mixtures) can be good carriers of ionophores. Ionophores have no withdrawal time prior to sale or slaughter of cattle, meaning that they can be consumed as part of the diet up until that time

Why should you consider using an ionophore in your operation?
Observations with Grazing Cattle

Growing cattle (i.e. stockers) and mature cows can benefit from the consumption of ionophores. Mature beef cattle grazing medium-to high-quality pasture have been observed to have increased weight gain and feed efficiency when provided an ionophore compared to non-supplemented cattle (Sprott et al., 1988). In stocker cattle, the use of ionophores can increase average daily gain by 5 to 15 percent. In a summary of 24 grazing trials, Potter and others (1986) reported that stocker cattle receiving 200 mg of monensin per head per day gained 0.20 pounds more per head per day compared to those that were not supplemented.

Considerations When "Stacked" with Other Technologies

Combining the use of ionophores with other production technologies such as growth promoting implants can result in improved growth and performance of beef cattle. Ionophores increase feed efficiency in the diet, while implants stimulate lean tissue growth. The improved rate of growth stimulated by growth promoting implants allows for the more efficient use of increased available energy in the diet from the ionophores.

Will ionophores be affected by changing FDA regulations regarding the use of antibiotics in feeds?

Beginning in January 2017, all antibiotics administered through livestock feed will require a Veterinary Feed Directive (VFD) per new regulations from the Food and Drug Administration. A VFD is like a prescription written by a veterinarian for administering antibiotics in livestock feed. However, only antibiotics that are medically important for treating human diseases will be impacted. Examples of drugs that will be affected include, but are not limited to, neomycin, tylosin, virginiamycin, chlortetracycline, and oxytetracycline.

Ionophores such as lasalocid and monensin will NOT require a VFD unless used in combination with a medically important antibiotic such as those listed above.

For additional information on the upcoming Veterinary Feed Directive guidance, visit: http ://www. aces.edu/ go/ 612

Helpful Contacts for Questions Regarding the Veterinary Feed Directive Guidance:

• State Veterinarian's Office -334-240-1455, [email protected]

• Alabama Farmer's Federation -Nathan Jaeger, 334-6134221, [email protected] org

• Alabama Cooperative Extension System -- Find Your Local Contact at www.aces.edu /directory.

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