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Understanding influencers of calf feed efficiency could help ranchers improve their herds

by Wyoming Livestock Roundup

Laramie – Studies conducted at the University of Wyoming look to prove feed efficiency is a heritable trait in cattle and hope to make it a usable tool for ranchers everywhere. 

After realizing she no longer wanted to attend medical school, University of Wyoming Professor Hannah Cunningham sought to combine her love of science with her background in cattle. 

“I grew up on a cow/calf operation in Kaycee,” Cunningham comments. “I really wanted to be able to integrate science in relation to the questions and concerns of cattle producers.”


“Feed efficiency is important in all aspects of the cattle industry,” says Cunningham. “We want cattle to be able to gain the most weight at the lowest cost.” 

Cunningham notes that feed costs account for nearly 70 percent of input costs for livestock producers in Wyoming and other western states. 

“For cow/calf producers, selecting females based on heritable efficiency traits will positively affect future generations of the herd and ultimately the bottom line,” says Cunningham. 

Cunningham explains the overarching goal of her research is to find a way to test microbes in the rumen that are indicators of feed efficiency. 

“We would eventually like to have a chute-side test to help ranchers determine feed efficiency and more effectively manage their probiotics from there,” she says.


Cunningham, along with a team of researchers, looked to assess feed efficiency associated with different type of birth and calf-rearing methods of weaned Angus and Charolais calves. The team noted the point of the study was to assess the feed efficiency of the two breeds, not make comparisons. 

Once separated by breed, the calves were subdivided again based on type of birth and calf rearing method. 

The Charolais group was separated into calves born vaginally but raised on milk replacer; a control group born vaginally and nursed on their mother; and a caesarian-section group nursed on their own mother.  

The Angus group was separated into the same groupings but with no caesarian-section group, due to issues regarding calf survival. Instead, the third Angus group consisted of calves born vaginally and given a probiotic paste within 24 hours of birth. 

After 60 days of testing, the data from the study was analyzed and organized by Cunningham and her team. The team looked at the age of the calf, starting weight, end weight, weight per day of age and residual feed intake. 

The study found Angus calves fed the probiotic at weaning had greater efficiency in comparison to the control group. Bottle feeding did not make a difference in either breed, and there was no difference in efficiency within the Charolais group. 


“This data is important for cattle producers in understanding the potential role of rumen microorganisms and maternal influence in cattle feed efficiency,” Cunningham comments. 

“We want to continue to look into how heritable the microbiome of the rumen is in cattle,” she says. “Data currently shows it is moderately heritable, but as of now, determining that requires very expensive testing.”

Cunningham notes there are a lot of studies in regards to the efficiency heritability in sheep, and many of the studies suggest it is, in fact a heritable trait. 

Callie Hanson is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to

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