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Utilizing Rumensin could provide benefits to all sectors of the beef industry

by Wyoming Livestock Roundup

Published on Feb. 8, 2020

“We have done a good job of using Rumensin technology in the majority of cattle on feed, but we really underutilize it in stocker cattle, growing cattle and on cow/calf operations,” states Dr. Frank White, beef cattle technical consultant at Elanco during the latest CattleFax Trends+ Cow/Calf webinar.

About Rumensin

            White explains Rumensin is an ionophore that is classified as an antibiotic and is not included in the Food and Drug Administration’s (FDA) medically important list since it is only used in animals. He further explains because there is no equivalent in human medicine, Rumensin does not require a Veterinary Feed Directive (VFD). 

            “Rumensin is a fermentative byproduct derived from the soil-borne bacteria streptomyces app.,” says White. “It is a feed additive that improves the energy utilization of feedstuff.” 

Understanding ruminants and how Rumensin works

            In order to understand how Rumensin works, White notes we must first understand what happens in the gut after feeding cattle. 

            He notes the biggest compartment in the cow’s stomach is the rumen and inside the rumen there are fungi, protozoan and bacteria.

            “The bacteria are a mixture of gram-negative and gram-positive bacteria and when we feed Rumensin, we are simply shifting the bacteria in the rumen from gram positive to gram negative,” White explains. 

            He continues, “This matters because there are starches in the grains and forages we feed our cattle and that starch or glucose is their number one energy source. Any animal with a simple stomach can break down glucose in grains and utilize the glucose. Cattle are also able to break the bonds in cellulose and utilize energy from forages.”

            White notes glucose is a six-carbon molecule.

            “There are bacteria in the rumen that take the six-carbon glucose and convert it into acetic acid, which is a two-carbon molecule. This means four carbons are lost through carbon dioxide and methane gas, which basically means the cow loses energy,” White says. 

            “There are also bacteria that make butyric acid, which is a four-carbon molecule,” White adds. “This means we are losing two carbons in the form of carbon dioxide and methane gas and therefore losing energy.” 

            He continues, “Another kind of bacteria in the rumen makes propionic acid out of glucose, and propionic acid is made up of two three-carbon molecules. Therefore, we are not losing any carbons or any energy. This is the best case scenario.” 

            White states Rumensin helps create this best case scenario by shifting the rumen to a gram-negative bacterial environment and making propionic acid from glucose.

            “The bottom line is we are going to be providing more energy to those cattle if we feed Rumensin,” White says.

Utilizing Rumensin in other sectors of the beef industry

            White notes Rumensin has been properly utilized in cattle living in confined situations such as feedlots. However, he believes it is underutilized in other sectors of the beef industry including in stocker cattle, growing cattle and on cow/calf operations.

            “The bottom line is the benefit of Rumensin in these cattle is an extra 0.2 pounds per head per day,” White states. “An extra 0.2 pounds means every five days we are going to get an extra pound of gain, and over 100 days, we will be getting 20 extra pounds.” 

            White notes Elanco has conducted numerous studies and found it doesn’t matter if cattle are on dead grass in the winter, green grass in the summer or forage at any time of year, their data consistently proves this extra 0.2 pounds of gain.

            “This extra 20 pounds is going to give a producer about $30 more, and what did that $30 cost?” White asks. “About $0.2 per head per day, so they are going to spend about two dollars per head and make an extra 30 dollars per head.”

            White says Rumensin also benefits mature cows. 

            “When feeding Rumensin to mature cows, we see an improvement in feed efficiency,” he states. “We did a study where we took cattle and fed them zero, 50 or 200 milligrams of Rumensin per day, which is on label.”

            “Those receiving no Rumensin were offered 100 percent of a feed ration, those given 50 milligrams Rumensin were offered 95 percent of a feed ration and those given 200 milligrams were offered 90 percent of a feed ration,” White continues. 

            White explains the results from this study found the cows and calves across all groups performed similarly.

            “Therefore, when feeding 200 milligrams of Rumensin, producers get an extra 10 percent in feed savings,” White says. 

            White notes Rumensin has the ability to also increase ADG and body condition score (BCS) while also controlling coccidiosis, which has been proved through several studies as well. 

Ways to feed Rumensin

            The last point White touches on is the different options available for producers when it comes to feeding Rumensin. 

            “My best advice to producers is to work with their feed company and nutritionist to find the best way to get Rumensin to their cattle,” White says. 

            He then goes on to note Rumensin can be fed as a mineral or with cake.

            “Another option might be for producers feeding a total mixed ration (TMR),” White states. “I think feeding Rumensin in a TMR is a no-brainer because producers will also get that 10 percent in feed savings we talked about earlier.” 

            White explains Elanco came up with a new, unique way to get Rumensin to cows. 

            “Our objective was to evaluate the accuracy and consistency of liquid Rumensin application in a molasses supplement on processed hay bales,” White says. “Our hypothesis was a spraying device would give us consistent application of Rumensin in a windrow during the processing of round bales so all cows would consume between 50 and 200 milligrams Rumensin, which is in line with the label.” 

            White explains they performed the study in North Dakota at several different times of the year because they wanted to know if the application would work in below-zero temperatures as well. 

            “We sprayed in December 2018, February 2019 and April 2019, and we really achieved an equal application through all three of those time periods,” White says. 

            He continues, “The results from this study showed first and foremost, this application method is safe. We found absolutely no issues with toxicity. We also found 94 percent of the samples we sent to the lab would provide on-label consumption recommendations of between 50 and 200 milligrams of Rumensin per head per day.”

            White encourages anyone interested in trying the spray method on their own operation to contact an Elanco representative. 

            Hannah Bugas is the assistant editor for the Wyoming Livestock Roundup. Send comments on this article to

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