The Role of RH in Cattle Feeding
When fed to steers and heifers during the last 28 to 42 days of the finishing period, RH has been shown to:
• Improve average daily gain
• Improve feed efficiency
• Maintain or show no effect on feed intake
• Increases hot carcass weight
• Maintain or show no effect on marbling score
• Improves carcass leanness
How RH Works
Ractopamine hydrochloride is classified as a beta-agonist and stimulates the beta receptors on cell surfaces. Your first response is “what the heck does that mean?” Let's first talk about what each of these components are. A receptor is a structure in or on a cell (in this case a muscle cell) that binds a specific substance. In this case the receptors bind RH which is a complex chemical compound. When RH is bound to the cell and thus introduced to the cells, it increases the rate of protein deposition in cattle, typically at the expense of fat deposition. Therefore, when fed, it increases the rate at which muscle is produced. This activity is commonly described as repartitioning or shifting from the normal deposition of one type of cell or tissue to another when the active compound is fed. The manufacturer claims that this effect does not interfere with meat quality or eating quality. One thing that should be added here is “when fed correctly.” Ractopamine hydrochloride is also the active ingredient in a swine feed additive called Paylean®. Research and practice in the feeding of RH in swine for extended periods of time can have an undesirable effect on the meat quality as well as the animal's ability to handle stress in later stages of it's life. Like any product, it is important that RH be fed appropriately and correctly.
Like most other additives, RH is fed at a very low level per head per day. The approved feeding rates range from 70 to 430 milligrams/head/day and 8.2 to 24.6 grams/ton of feed (90 percent dry matter basis). The most cost effective dose is believed to be around 200 milligrams/head/day. Tables 1 and 2 illustrate some pooled performance data fed varying levels of RH and at two different feeding periods. It should be noted that the feeding of RH occurs at the end of the feeding period and is not an on-going practice. Current recommendations are to feed the product from 30 to 45 days before harvest.
The Results
Research has shown that the extra live weight gain corresponded to a 14.1 lb heavier hot carcass weight in steers and a 6.3 lb heavier hot carcass weight in heifers. Data gathered from 28 day feeding trials shows a 14 lb heavier hot carcass weight in steers and a 5 lb heavier hot carcass weight in heifers. Future research will further define this difference between steers and heifers in hot carcass weight response. We already know that steers and heifers deposit lean and fat tissues differently, thus the effect that RH has on the genders would vary as well.
Currently Optaflexx has been fed to a variety of English and Continental breeds and crosses. All the tested breeds have responded to some degree. At this point in time there has not been a lot of information regarding the response from Holsteins or Brahman cattle. Once again, we know that the breeds differ somewhat in their predisposition to put on lean or fat tissue. This can also vary depending on age or maturity and we also know that this is affected by breed. What this tells us is that the effect RH has will depend on sex, breed, age and maturity and subsequent interrelationships.
Aside from the changes noted in gains, feed efficiency and so on, the most important factor we have to consider is the effect on carcass characteristics because this determines the true value of the calf – how much meat and what quality of meat is produced by the individual.
Current data suggests that dressing percentage is increased in steers but not significantly changed in heifers fed RH at 200 mg/hd/day. While the increase in steer dressing percentage is statistically significant P<0.05 the numerical difference is small enough that it may not be apparent to producers. Thus the changes may not be readily apparent unless the producer is feeding large numbers of cattle.
Yield grade is unaffected in both steers and heifers when fed 200 milligrams per head per day. Producers need to consider whether to sell their RH fed cattle on a live weight basis, in the meat or on a grid. Consideration must be given to whether they are feeding steers or heifers. Additional detailed performance data is available from Elanco or certain Universities and can be helpful with these decisions.
Planning use of the Product
The use of any additive requires consideration and planning. Thought is required to determine if utilizing RH is a good decision for a producer. Like many additives Optaflexx adds significant cost to the feeding program. Every effort must be made to achieve the maximum financial return. As discussed earlier research indicates that the best return on investment occurs if Optaflexx is fed at the rate of 200 mg/hd/day for 28 days. This leads to some marketing implications that are not apparent with other feed additives. Prior to starting Optaflexx producers need to accurately predict when they are going to market the pen of cattle. Ideally, cattle will be sent to slaughter after 28 days on Optaflexx. Cattle can be marketed anytime within the 28 to 42 day window but feeding much past 28 days will likely lessen the economic value of the Optaflexx feeding program. Additionally, sorting needs to be done before cattle go on the Optaflexx program. The approval is for the last 28 to 42 days on feed. The entire pen of cattle needs to be sent to slaughter within the 28 to 42 day window and preferably soon after 28 days.
Use in Show Cattle
A similar product has been introduced for use in show cattle, primarily show steers. This product, marketed as Showflexx™, has shown similar results in cattle on the show circuit as in conventional feeding programs, with increases in muscle deposition at a late date of production. Feeding of the product the last 30 to 45 days prior to a given show date will provide for additional muscle expression in the animal. However, the feeder/showman needs to be aware that this will be at the expense of fat deposition. Thus the animal needs to be well finished prior to starting the Showflexx program. This also means that harder finishing animals may not be as good of a candidate for the program as other, more readily finishing animals.
Conclusions
Like any product RH has its upsides and down sides. Given the implications on performance, however, the feeding of RH probably requires more careful consideration and planning than many other additives that are available on the market.
Dr. Steve Blezinger is and nutritional and management consultant with an office in Sulphur Springs Texas. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at sblez@direcway.com. Also, visit BLN's web page at www.blnconsult.com.
