Efficient, high-marbling beef

Weak correlation between traits makes good news for cattlemen.

by Morgan Marley

Everybody who makes a living in the beef industry wants more efficiency, especially if it doesn’t sacrifice carcass quality. Animal scientist Dean Pringle says a University of Georgia (UGA) team is finding more ways to satisfy both input and output goals.

Recently published, “The impact of selection using residual average daily gain and marbling EPDs (expected progeny differences) on growth, performance and carcass traits in Angus steers,” shows no need to back away from one target to hit the others. That paper by graduate student Rachael Detweiler and others is the first in what could be a long series from UGA.

It’s backed by a 210-cow commercial Angus herd at the Northwest Georgia Branch Experiment Station, bred since 2011 to registered Angus bulls selected to create four unique herds for exploring those relationships.

“Our criteria were high efficiency and low efficiency; and within the efficiency groups, high marbling and breed-average marbling,” Pringle says. “Our first objective was to evaluate and verify that selection for residual average daily gain (RADG) actually did result in changes in feed efficiency.”

It did, according to the current analysis of data from 191 steer progeny across three years. Details show more.

Pringle’s meat science background led to broadening the objectives, since protein is generally produced more efficiently than fat.

“I started worrying about that,” he says. “If we get these animals more efficient, converting feed to gain, are we going to begin to select against lipid and marbling deposition in those animals?”

Data results eased Pringle’s mind on that concern.

A closer look at the carcass data underscores the quality already bred into the UGA herd (see Chart).

Across all levels of efficiency, more than 79% of steers from Angus bulls selected for just average marbling had enough to qualify for the Certified Angus Beef ® (CAB®) brand, including 21.8% CAB Prime.

However, with few concerns about backing away from higher marbling, bulls in the breed’s top 10th percentile for that trait could produce steers with enough marbling for nearly 91% brand acceptance. That’s with 37.4% CAB Prime.

“So we were able to have lowly efficient animals that were high in marbling,” Pringle says. “We were able to have highly efficient animals that were high in marbling. In the Angus breed, those two traits do not appear to be highly genetically linked.”

The models created for ongoing UGA research allow studying both the biology and physiology of these economically important traits, he adds. Now eight calving seasons into creating the four sub-herds, researchers are comparing first- to second- and now to third-generation progeny.

“We’re looking at differences between microbes in the rumen and the rest of the GI tract for each of the four lines,” Pringle says. “We’re looking at liver tissue to see if there are other genes being up- or down-regulated as we continue to select for marbling and efficiency.”

Those are the more straightforward examples.

“This is going to sound a little bit off the wall, but we’ve got a scientist who studies taste buds in different animals,” bringing feed palatability study to a new level, Pringle reveals. “What if cattle eat more or less because they like what they’re eating more or less? What if the differences in intake are related to differences in their taste buds?”  

Off the wall or not, the work fits UGA’s research focus.

“I certainly don’t think the beef industry is done selecting for output traits like growth and carcass, but we’re starting to see a slowing of progress for some traits,” Pringle says. “So it’s important for us to look at these input traits like feed efficiency to help reduce input costs to the producer.”

That includes such behavior factors as how often animals come up to eat, and whether individuals prefer small meals or are “binge eaters.”

The scope of work may also expand to reproductive efficiency for longer-term productivity.

“From a 30,000-foot view, it does not appear that we are negatively impacting reproduction,” he says, “but we haven’t really dug into that yet. Maybe we need to prioritize knocking the lower-efficiency cattle out of the herd more than selecting for the higher end, but we need to look deeper into the reproductive performance.”