Early Reports of Feedlot Performance and Carcass Quality of Cattle When Feeding Experior

By Jerad Jaborek

Experior is an Elanco Animal Health product with the active ingredient lubabegron fumerate. It received Food and Drug Administration (FDA) approval in 2018 to reduce ammonia gas emissions from cattle during the final 14 to 91 days prior to slaughter. Experior (lubabegron) is a beta-agonist (β-AA) and beta-antagonist, meaning it can bind to beta-agonist receptors (β-AR) found on various tissues across the body to elicit its metabolic effects. Unlike other commercially approved β-AA (i.e., Zilmax (zilpaterol hydrochloride) and Optaflexx (ractopamine hydrochloride) that are agonistic at β-AR 1 and 2, Experior (lubabegron) is a beta-antagonist at β-AR 1 and 2, but agonistic at β-AR 3. The lack of desensitization at β-AR 3 to elicit metabolic effects allows for the longer feeding period duration relative to other β-AA products previously mentioned.

Beta-agonists are recognized as repartitioning agents because they shift nutrient utilization towards protein synthesis and away from lipid synthesis, resulting in greater muscle growth and less fat deposition, respectively. Unlike other β-AA that highlight their claim to increase body weight gain, improve feed efficiency, and increase carcass leanness, Experior has a novel label claim to reduce ammonia emissions per unit of body weight from cattle and states that it is not yet proven to increase body weight gain, improve feed efficiency and increase carcass leanness. Therefore, the highly anticipated question is does Experior affect the feedlot performance and carcass quality of cattle? 

Producers choosing to feed Experior must enter into a user agreement with Elanco and agree to feed Experior at a specified dose, duration, provide feeding records and animal health data and follow a four-day voluntary withdrawal period to control tissue residues before sending cattle to slaughter. The user agreement indicates producers should feed 36 mg/head/day (~3.2 g/ton) for between 28 to 63 days with the four-day withdrawal period. Even though Experior is approved to feed at 1.25 to 4.54 g/ton (1.39 to 5 mg/kg complete diet 90% DM) and provide 13 to 90 mg lubabegron/head/day to steers and heifers intended for slaughter during the final 14 to 91 days on feed without a required withdrawal period. The user agreement is to help ensure the sustainable use of Experior in the beef industry.

Since Experior is relatively new and approved cattle feeding product, only a few cattle feeding studies have been completed. However, it is expected that many more peer reviewed research studies to be published in the upcoming months and years. Below is a brief summation of the research findings on feedlot cattle performance and carcass quality as we approach the end of 2024.

To date, five manuscripts have been published comparing feeding Experior versus not feeding Experior, as well as investigating different doses, withdrawal times and feeding durations. A study conducted at UC-Davis by Teeter and colleagues demonstrated the reduced ammonia emission claims when feeding Experior at different doses (0, 1.38, 5.5, and 22.0 mg/kg DM). During the 91-day study, average daily gain (ADG) tended to increase and feed efficiency improved while feeding Experior to crossbred beef steers and heifers. Carcass weight, dressing percentage, and ribeye area also increased, while marbling score tended to decrease and tenderness decreased. A study conducted at Cactus Cattle Feeders by Kube and others found similar results with greater final weights, ADG, feed efficiency, feed intake, carcass weight, dressing percentage, ribeye area and less backfat and marbling in implanted crossbred beef steers. In a study investigating different Experior withdrawal times (0, 2, 4, 6, 8, 16 days) before slaughter, similar performance and carcass outcomes were observed as previously mentioned.

Other studies investigated the effects of feeding duration of Experior. Conducted in Idaho, crossbred beef steers were fed either (0, 1.5, 3.5 or 5.5 mg/kg DM) of Experior and fed for either 28, 56 or 84 days. Similar to the previously mentioned Experior dosage studies, greater final weights, ADG, feed efficiency, feed intake, carcass weight, dressing percentage, ribeye area and less backfat and marbling were observed with feeding Experior. Changes to feed efficiency, carcass weight, dressing percentage and marbling score responses were linear with increasing dosage. Increasing the feeding duration of Experior linearly increased final body weight, ADG, feed efficiency and feed intake. Similar responses were noted in a study focusing on feeding Experior (0, 28, 56, 84 days) to Holstein steers. Feeding Experior for longer durations increased ADG, improved feed efficiency, increased carcass weight, dressing percentage and ribeye area, but decreased backfat and marbling score.

Clearly, feeding Experior increases ADG and improves feed efficiency, which results in greater final live weights, carcass weights and dressing percentages due to the increased muscle growth. However, carcasses may have less backfat and have less marbling deposition, which can negatively impact USDA quality grades. This reduction in marbling score and quality grade can be partly attributed to the dilution effect caused by the increased surface area of the ribeye compared with the relatively smaller contribution of marbling.

Two studies have also compared feeding cattle Experior against Optaflexx, although at different dosages. In a Kansas study by McAtee and others, crossbred beef steers demonstrated greater final weights, ADG, feed efficiency, carcass weight, dressing percentage, ribeye area and a lesser feed intake and marbling score. In a Canadian study, Limousin × Jersey steers demonstrated greater ADG, improved feed efficiency, lesser feed intake, greater carcass weights, dressing percentages, ribeye area and lesser marbling scores when fed Experior for 56 days compared with Optaflex for 28 days. It is possible that feeding duration could be influencing the differences observed in these two studies when comparing results of feeding Experior and Optaflexx to cattle.

Here are a couple other interesting observations noticed from these studies. Many of these studies removed any implants prior to initiation of the study, likely to eliminate any possible interaction with feeding Experior. Therefore, it is not yet clear if or how different implants may interact while Experior is being fed in terms of performance and carcass differences. Secondly, the crude protein concentration of the diets fed in these studies were greater than those typically required by cattle of their size. Crude protein concentrations were 14.2, 14.6, 13.7, 14.6, 15.0, 15.9 and 12.0% in their order of mention above. It is unknown whether greater concentrations of crude protein were fed due to cheaper dietary cost or an expected requirement when feeding Experior. Future research will hopefully provide more answers to these questions.

If you have questions or would like to discuss further, reach out to the Michigan State University Extension Beef Team experts. You can contact the author, Jerad Jaborek, at jaborekj@msu.edu.