Implant Strategy Study Shows Carcass Quality Differences

The cattle industry’s understanding of implant management and its influences on production and carcass traits has increased dramatically in recent years. For example, we now know that various growth-promoting compounds have varying effects on carcass quality, and zeranol is the compound of choice for initial implant use. In the feedyard study reported here, several issues are addressed. The conclusion is that the most appropriate implant strategy is zeranol (Ralgro® implants) on Day 1 followed by trenbolone acetate plus estradiol (Revalor®-S) on Day 70.

Study Design

This study was conducted at the Agri Research Center, Inc., Canyon, Texas, under the supervision of David Bechtol, DVM. Three hundred fifty steers of moderate frame size and weighing 556 pounds were randomly assigned to one of seven treatment groups, shown in Table 1. Each group consisted of 50 calves. Individual body weights for all steers were determined initially and after 70, 100 and 155 days on feed.

Harvest processing was done by a major commercial packer, which provided individual animal data on hot carcass weight (HCW) and USDA Quality and Yield Grades. Measurements of ribeye area, ribfat depth and KPH fat, and assessment of marbling and maturity were performed by Cattleman’s Carcass Data Service, under the supervision of Ted Montgomery, Ph.D.

Results

The results were consistent with expectations based on previous research with these growth promotants.

  • Ralgro implants continue to be the initial implant of choice. It allowed marbling to develop similarly to non-implanted steers and had no detrimental effect on quality grade distributions
  • Ralgro/Revalor-S increased average daily gain (ADG) 20 percent over controls and reduced feed conversion (F/G) 8.4 percent from controls, without adversely affecting carcass quality grades. Ralgro/Revalor-S calves graded 81 percent Choice or higher, while the controls graded 77 percent Choice or higher.
  • The Magnum/Revalor-S strategy provided similar ADG and carcass responses, but that group was 5.5 percent less feed efficient than the Ralgro/Revalor-S group. This difference is probably due to the heavier average body weight resulting from the Magnum implant during the initial 70 days.
  • The Magnum/Magnum strategy delivered both performance and carcass returns, supporting Magnum’s role as an initial 100-day implant and as a terminal implant.
  • Magnum/Magnum had slightly less effect than Magnum/Synovex Plus on live animal performance, ADG and F/G, which equated to less than $3 per head. Conversely, animals receiving Magnum as a terminal implant had higher carcass quality (73 percent Choice or higher) than the animals receiving Synovex Plus (59 percent Choice or higher), which more than offset the performance difference.
  • The dollar value of higher carcass quality is shown in Table 2. Clear economic advantages resulted from any implant strategy that incorporated zeranol.

*Per 100 head. $6/cwt HCW as average Choice/Select spread.

$3/cwt HCW as Certified Angus Beef (CAB) premium.

Conclusions

This study concludes that Ralgro/Revalor-S was the most appropriate implant strategy when considering production and carcass variables. For cattle on feed 200-220 days, Ralgro Magnum implants can be used as an initial implant for 100 to 110 days and as a terminal implant for the remaining 100 to 110 days, with slaughter at 1,200 to 1,250 pounds.

For full details of this study, contact your Merck Animal Health representative or call Livestock Technical Service at 1-800-211-3573.