Beef Team member says size really does matter with cows
By Heather Thorstensen
ROCHESTER, Minn. — The message to beef producers during the 2009 Minnesota Beef Cow/Calf Days was that size does matter.
Members of the University of Minnesota’s Beef Research and Education Team spoke to producers in 10 cities about cow size this month. Their Feb. 19 meeting in Rochester drew 90 attendees.
Beef Team member Ryon Walker gave the keynote presentation created by Bryan McMurry of Cargill Animal Nutrition, who did not attend the Rochester meeting.
Cow-calf producers can’t control all their costs, said Walker, but they can control cow size to improve efficiency. Larger cows consume more energy in the form of feed than smaller cows, and that might be detrimental to producers’ bottom line.
According to McMurry, for every 100 pounds of increase in mature cow body weight, a producer will pay $15 to $20 more per head per year for hay, supplements and minerals.
Research suggests a larger cow is less likely to produce calves at an ideal weaning weight, which Walker said is 50 percent of the cow’s body weight.
"As long as she weans 50 percent, then she’s efficient," he said.
A study at North Dakota State University’s Dickinson Research Extension Center found that a 1,200-pound cow group produced calves with a weaning weight at 49.7 percent of their weight, while a 1,500-pound cow group produced calves with a weaning weight at only 38.6 percent of their weight.
The heavier cows require more feed, but are less efficient at producing calves.
From 1975 to 2005, the average U.S. mature cow has increased in size by approximately 300 pounds because producers have been selecting for growth traits and there’s been improvements in health and nutrition programs. Even though the country’s cattle herd numbers have dropped by 13 million head in 30 years, the industry’s forage requirements have gone mostly unchanged because cows are bigger.
The average U.S. cow size now is 1,350 pounds, which Walker said is a good weight, but producers may start seeing a drop in efficiency in cows that weigh more.
"We’re learning what causes it," said Walker. "Hopefully producers think about cow weights and efficiencies."
He suggested producers start to re-evaluate the value of selecting for growth traits. He also told producers to know their mature cows’ weights, calf weaning weights and feed efficiencies so they can determine where to make improvements.
If producers want to replace big cows, they may think about selling their top end heifers, which are typically the heaviest, and keep heifers from smaller, productive cows as replacements. If producers have to look outside their herd for replacement females, look for those that have been bred for moderate size and maternal traits.