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Effect of implants: UW study sees increased gains, improved efficiency on backgrounded calves with implants

by Wyoming Livestock Roundup

Efforts to evolve beef production to improve cattle efficiency and producer profitability are never ending. In a recent study conducted at the University of Wyoming (UW) James C. Hageman Sustainable Agriculture Research and Extension Center (SAREC) at Lingle, researchers looked into cattle performance and the feeding economics of implanting weaned calves during a winter drylot feeding program.  

 Study background

“Many producers will background calves, and a lot of times, they won’t implant them in the fall,” says UW Extension Beef Cattle Specialist and SAREC Director Dr. Steve Paisley. “They’ll buy calves when prices are low in the fall and will often background the calves in a drylot, basically holding them until they can go on grass the following spring.”

Some of Paisley’s previous work found producers benefitted between $12 and $21 per head by implanting steers during the winter. The steers maintained heavier weights through the end of their time at the feedlot following the winter backgrounding period, which resulted in heavier carcass weights. 

In this study, Paisley and his research team utilized the Zoetis Synovex Choice implant on weaned steer and heifer calves to measure the effects of the implant on performance and feeding economics during conditions typically found on a southeastern Wyoming winter drylot program. The 80-day study utilized weight gain, feed intake, feed efficiency and cost of gain to evaluate differences between calves with and without implants. 

The Synovex Choice implant is reported to increase average daily gain (ADG) and improve feed efficiency in heifers and helps to boost weight gain in steers, according to Zoetis. 

“The original idea of the study was to mimic producers in the area,” Paisley explains. “We wanted to not push the calves as far as gain goes, to see whether or not there is a benefit to implanting calves.”      

Calves were fed a starter ration consisting of corn, corn silage, ground alfalfa and a protein supplement containing Rumensin, an ionophore commonly used to control coccidiosis. 

“We fed our lowest energy startup diet and the calves still gained an impressive amount of weight, way more than we wanted them to,” Paisley notes.

While tremendous weight gain wasn’t planned, the study still boasts compelling results. 

Study results 

“What was interesting to me was feed efficiency dramatically improved,” shares Paisley. “Average daily gain increased, which is what we would expect, and feed intakes were nearly identical.” 

Both measures of feed efficiency, feed-to-gain ratio and gain-to-feed ratio, improved in calves implanted with Synovex Choice on the study. Calves that didn’t receive an implant were fed, on average, 5.89 pounds of feed for each pound of gain, while implanted calves were fed approximately 5.41 pounds of feed per pound of gain.

“Economically speaking, an improvement from 5.8 pounds of feed per pound of gain to 5.4 pounds of feed per pound of gain, from a feed efficiency standpoint is a huge number,” Paisley states.  “For producers, that is worth paying attention to.”

On the study, non-implanted calves gained approximately 264 pounds, for an ADG of 3.72 pounds per day, compared to implanted calves, which gained 286 pounds, for an ADG of 4.02 pounds per day. 

Dry matter feed intake was similar for both sets of calves at 21.47 pounds per day in the non-implanted calves and 21.49 pounds per day for implanted calves. The feed cost per pound of gain was 63 cents for non-implanted calves and 58 cents for implanted calves. 

“The fact that those calves gained three-tenths of a pound more on exactly the same amount of feed is very interesting,” shares Paisley. 

“Many times, I think producers don’t think to implant cattle if they aren’t pushing them in the feedlot,” Paisley says. “But, there is still a benefit to implanting. We improved gain, and we improved efficiency.”

Averi Hales is the editor for the Wyoming Livestock Roundup. Send comments on this article to

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