Mike Jarosz, Ph.D.
Moving into spring/early summer brings about many calf-fed cattle close to finishing in the feedlots. A set of additives called beta agonists may be worth considering in your operation to aid cattle performance while providing a return on the cost of the additives. Usage of beta-agonists has received attention in regards to cattle health, stress, and handling. Consult with your nutrition representative or beta agonist supplier for programs and information to best implement the beta-agonist.
Beta-agonists such as ractopamine hydrochloride act in the animal in a way described as partitioning agents, directing more nutrients to muscle development than a fat deposition. Ultimately, at the cellular level beta-agonists bind to specific cell receptors and a cascade of events ensue stimulating mechanisms to increase protein deposition, decrease fat deposition, and increase fat degradation. With these cellular changes, more nutrients are directed toward a more efficient net protein deposition in the animal.
A variety of research projects have been performed evaluating the usage of beta-agonists when fed to cattle at different levels, steers, heifers, various cattle ages, time periods, implant programs, etc. Lean et al., 2014 performed a meta-analysis of projects conducted with beta agonists and found feeding cattle ractopamine resulted in an average of a 16.2 lb. increase in carcass weight. Following is a table that summarizes the usage of ractopamine and the influence the additive has on various performance measures in cattle.
Average animal performance influences by beta agonist. Adapted from Radunz, 2011
Item |
Ractopamine hydrochloride |
| Fed rate, mg/hd/d* | 70-430 |
| Optimal level, mg/hd/d* | 300 |
| Duration of feeding, d* | 28-42 |
| Optimal duration of feeding, d* | 28-35 |
| Withdrawal time, d* | None |
| Dry Matter Intake, lb./hd/d | Minimal |
| Average daily gain, lb./hd/d | Increase 9-21% |
| Feed efficiency, Feed:Gain | Improve 9-21% |
| Dressing percent | Minimal impact |
| Hot carcass weight, lb. | 10-25 lb. increase |
| Ribeye area, sq. in. | Increase up to 0.5 |
| Marbling | Minimal impact |
| Tenderness | Minimal impact |
*Follow label directions.
Upon considering using beta agonists, realize every cattle feeding situation is unique and steers have a greater response than heifers. In regards to an estimated return on investment when using ractopamine when averaged across both sexes (Elanco Animal Health communication), the estimated increase in carcass weight is 17 lb/hd. @ $2.05/lb. = $34.85/hd extra value. If ractopamine is fed for 30 days @300 mg/h/d @$0.50/hd/d = $15.00/hd. cost for the additive. The net result is a $19.85/hd return on investment based on extra carcass weight alone (note: performance, cattle prices, additive price, etc. will vary).
When feeding beta-agonists, supplement strategies will vary depending on the number of days fed, the number of cattle, supplement type, etc. Keep in mind only part of the cattle in the feedlot would be fed beta-agonist their last 28-42 days on feed, therefore, multiple supplements may be required. Beta-agonists are approved and can be delivered in a liquid feed supplement, contact your QLF representative for options to deliver beta agonist in your specific feeding scenario.
Lean, Ian J., John M. Thompson, and Frank R. Dunshea. A meta-analysis of zilpaterol and ractopamine effects on feedlot performance, carcass traits, and shear strength of meat in cattle. PLoSOne. 2014.
Radunz, Amy E. Use of beta-agonists as growth-promoting feed additives for finishing beef cattle.