Genetic improvement in beef cattle means jumping hurdles or “antagonisms” among the traits.

When animal scientist Dan Loy signed on with Iowa State University (ISU) as a feedlot specialist 40 years ago, he brought along a commercial Angus background. Best practices for the herds supplying feedlots then were crossbreeding and balanced selection for maternal and growth traits.

Stockmen had to use single-trait “heifer bulls,” because there weren’t many bulls with calving ease along with growth. If anybody paid attention to marbling, they probably noticed some bulls above average there had little else to recommend them.

Science charted and measured the antagonisms for decades, and the Certified Angus Beef (CAB) brand sponsored a literature review at Kansas State University in 1999, updated in 2007. That was revisited by researchers at Virginia Tech in 2013. The consensus has always found little or no correlation between marbling and other traits.

That lack of correlation says marbling, maternal function and growth should all fit together in the same cow.

Before those studies, in 1996, Loy and ISU began gathering data on calves from the University’s two Angus herds, built on either marbling or ribeye emphasis. Early on, results were not much publicized and after six years, the ribeye herd was discontinued when an ultrasound technician moved on.

It took many years to build up enough volume to achieve significance in data from the McNay Farms herd near Chariton, Iowa. But that time has come with the white paper’s publication, now available online at

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