Growth promotants’ role in making cattle bigger unclear

STE. ROSE DU LAC, Man. — Research shows that slaughter steers are 29 percent heavier and heifers are 45 percent heavier than they were three decades ago.

However, it’s unclear how much growth promotants have contributed to those gains.

Tim McAllister, an Agriculture Canada cattle nutrition expert in Lethbridge, is leading a team of scientists looking at the environmental impact of Canada’s beef industry. Growth promotants, or hormones, are responsible for a portion of production improvements from 1981 to 2011, but nailing down a percentage wasn’t part of the study.

“It’s very difficult to get information … because it depends on what growth promotant you’re talking about, how it was administered and what was the nature of the cattle it was administered to,” he said.

“We just don’t have that kind of data … to specifically answer that question.”

Studies suggest growth promotants improve cattle feed efficiency by five to 20 percent.

“I would say they’re probably more universally used than they were in 1981,” McAllister said.

“We know it’s a contributing factor to the efficiencies.”

Growth hormones are controversial because some consumers believe they aren’t natural and contaminate beef with unnecessary compounds.

McAllister said research has repeatedly demonstrated that growth promotants are safe.

They may be contentious, but growth promotants likely reduce cattle’s environmental impact. Fewer animals are needed to produce beef if animals reach slaughter weight more rapidly, which reduces methane emissions.

McAllister and his colleagues determined that improvements in genetics, feed efficiency and forage quality decreased methane emissions, per kilogram of beef, by 15 percent from 1981 to 2011.

Cattle producers can further reduce those emissions by using biotechnology and other innovations.

“A lot of that will (depend) upon society’s acceptance of advanced technologies,” McAllister said.

“Because of the developments in genomics and meta-genomics … that weren’t available five to 10 years ago … those give us the ability to be more refined, more calculated in the approaches for improvement.”

Growth implants are an example of technology that could disappear, McAllister said.

If North American consumers reject the use of growth promotants, as they have in Europe, the beef industry will struggle to maintain production gains and cut greenhouse gas emissions in the future.

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