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RX3™ Immune Support Technology FAQ

Nov 30, 2020

What is RX3™?

RX3™ is a precise combination of prebiotics, probiotics, and plant extracts to help aid calves in the fight against respiratory challenges. Probiotics aid in gut health and immune system function. Prebiotics provide food substrates to support the growth of rumen microbes. Plant extracts play a functional role in digestion and inflammation. RX3™ components fit into an All-Natural Program. Purina® has the exclusive rights to RX3™, which is a product of PMI Nutritional Additives.

How does RX3™ work?

RX3™ primes the immune system to support overall calf health, reduce treatment cost, and set calves up for a healthy future. The three R’s to RX3™ are Recognize, Respond, and Recover. The immune system is primed and ready to recognize pathogens. The appropriate response is elicited from the immune system to eliminate pathogens, and the animal recovers sooner and calves look healthier quicker.

Where will Purina Starters with RX3™ be manufactured? Will there be a name change for these products?

Purina® starters are available in the same locations as the previous starter products. There was no name change, however, new skus were set up for these products. Additionally, each starter bag will now have a sticker reading “Now with RX3™ Immune Support Technology” on them.

Is RX3™ an antibiotic? Does it replace an antibiotic? Does it replace a vaccination program?

RX3™ is not an antibiotic (drug) and does not require a VFD. RX3™ is a preventative measure, which complements a vaccine program. RX3™ is not a replacement for treatments upon arrival for high stress, high risk calves, where a significant morbidity rate is expected. If calves become sick during the weaning/receiving program, the local veterinarian needs to be contacted to determine the appropriate treatment.

What effect does RX3™ have on sickness rate during the weaning or receiving period?

It reduces the amount of morbidity in calves. Our data show that of the calves that got sick, they express signs of sickness two days sooner allowing us to identify and treat them quicker.

What are the recommended days of use for starters with RX3™?

Our weaned calf programs are recommended to be fed for 21 to 28 days. Additional performance has been reported in the third week of the starter program, thus driving the importance of feeding through this time period. RX3™ has been tested out to 49 days in backgrounding diets, with positive returns on gain and feed efficiency, and reduced morbidity.

What happens if I don’t feed for the recommended time frame? How long does it take for RX3™ to begin


The components of RX3™ begin working on day 1, however, fully priming that immune system takes time. In performance studies, of the calves that got sick, those offered RX3™ showed signs of sickness on average by day 16 compared to day 18 in control calves. It is important to remember that if we are weaning ranch fresh calves, they are typically going to express signs of sickness on day 7 to 10. Changing the nutritional program prior to or during this timeframe could potentially increase the risk of cattle getting sick. We need to remind cattle owners that we need to feed through this frame to insure cattle get off to a good start.

Is RX3™ available in tubs and liquids?

No, RX3™ is not available in any of our Wind & Rain® Mineral tubs, Purina® Stress Tub, or any of our liquid products at this time.

For more information, please contact your CFE Beef Team salesperson or:

Joe Nilles, 712-470-4803, 

Ethan Blom, Ph.D, 507-227-1968,

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