An age-old debate in the cattle industry has always been what is the “perfect” cow size. According to Kenny Burdine, University of Kentucky livestock agriculture economist, there is no one-size-fits-all cow. The optimum-sized cow is one that works in your production and marketing environment and weans off enough pounds each year to be profitable.
“I have never been one to believe that an ‘optimal’ cow size exists,” Burdine says in a recent Cattle Market Notes Weekly. “Every farm is unique and operates in a different production and market environment. Whenever this question comes up, I simply reply that I don’t really care what cows weigh, as long as they are weaning enough pounds of calf each year to be profitable.”
Mark Johnson, Oklahoma State University beef cattle breeding specialist, says the U.S. cow herd has been steadily increasing in mature weight for several decades. This is largely the result of selection pressure applied to increasing weaning and yearling weights.
“Because of the positive genetic correlations between weights taken at all stages of life, mature weight has increased even though that has not been the objective,” he explains.
Have calf weaning weights increased in proportion with cow weights?
“There’s a growing amount of empirical evidence that tells us there’s about a 10 to one relationship, meaning that if we increase mature cow size by about 100 lb., we only see 10 lb. of increase in a calf weaning weight,” Johnson explains in a recent OSU Cow-Calf Corner article.
Research demonstrates as cows get bigger they wean off a lower percentage of their mature weight.
“It’s easier for a 1,000-lb. cow to wean off close to 45% to 50% of her mature weight, whereas when cows get 1,400 lb. to 1,600 lb., it’s more of a struggle, and they’re probably going to be at 30 some percent, maybe get as high as 40% on average of their mature weight,” he says.
What is the producer’s perspective on cow weights?
“As cow-calf producers we have to balance mature cow size with the grass,” explains Sam Hands, of Triangle H Inc. Hands and his daughter, Marisa Kleysteuber, own and operate Triangle H, which includes a cow-calf operation, and a feedlot located south of Garden City, Kan.
During his 65 years in the cattle business, Hands says he has witnessed changes in production efficiency and pounds of beef produced per cow per acre. He shares an example comparing a cow from when he returned home from college to today’s average cow.
In the early ’70s cows were averaging 1,000 lb. and weaning off 425-lb. calves. Today, due improved genetics, the cows average 1,400 lb. and wean off 600-lb. calves. But water and grass resources can only handle and produce so many pounds. So today, to produce the same pounds of beef, the land can carry 71 cows compared to previously 100 cows.
“We can push Mother Nature and grass so far, but when we push too far, then we have cows out of condition, we have open cows, we have lighter calves,” he explains.
Hands admits due to genetic improvement in his cow herd by using expected progeny differences (EPDs) and other selection tools he has been able to keep the balance. With calves growing faster, they can calve later and wean earlier and still get the additional pounds on grass in about 45 days less time.
Which cows should a producer cull?
Burdine says producers make culling decisions each year based on the best information they have at the time. He admits record keeping has never been high on the list of things cow-calf producers enjoy, but it is extremely important and should be used to drive culling decisions.
“Well managed cow-calf operations track weaning weights on individual calves and tie each calf back to its dam,” Burdine says. “By doing that, productivity can be measured for each individual cow. On the other hand, it is nearly impossible to track production costs on an individual cow basis. Producers with good financial records likely have a solid understanding of what it costs them to maintain the average cow in their herds.”
This distinction is important when one considers how to use production records to make culling decisions. Larger cows tend to wean larger calves, but they are also more expensive to own.
“While it is not easy to observe, they will consume more hay, feed, pasture and mineral as they maintain their larger bodies, and one can make a case that vet/medicine, yardage, transportation and other expenses will be higher for larger cows too,” he says. “The simple point being that if one is making culling decisions based on calf weaning weights alone, they are likely to be disproportionately culling more of their smaller cows. By doing this over time, the average size of their cows increases, and their costs trend upward.”
Burdine says he put together an Extension presentation aimed encouraging producers to consider cow size in their culling decisions.
“I used a simple budget approach and adjusted costs as best as I could for various sized cows,” he explains. “I even included a higher cull value on those larger cows, which is relevant to the discussion. Using this approach, it appeared that an operation needed to wean about 50 more pounds of calf for every additional 100 lb. of mature cow they were maintaining.”
He admits this approach is not perfect, but it illustrates the concept he was trying to prove that basing cow culling decisions solely on the calf’s weaning weight can be misleading.
“While I don’t think there is an ‘optimal’ sized cow, I know those larger cows must be weaning larger calves to earn their keep,” Burdine summarizes. “And the only way to do that is to consider calf weaning weights in relation to the weight of the cows.”
Can mature size be managed while increasing weaning weights?
Johnson says increasing growth is important.
“Obviously, in the cow-calf sector, we sell calves based on pay weight,” he explains. “That’s our primary profit center, and we should put selection pressure on growth, be it weaning or yearling, if we’re retaining ownership past that, maybe it’s those final finished weights or carcass weights. But that needs to be selection pressure applied relative to mature cow size.”
There are positive genetic relationships between birth weight, weaning weight, yearling weight, postweaning gain, mature weight, mature height, finish weights and carcass weights.
Johnson reminds producers that by using expected progeny differences (EPDs), producers have been able to keep birth weights down and maintain calving ease, the past 30-plus years while spiking weaning weight and yearling weight.
“What have we not done? Probably put enough selection pressure on the backside of that growth curve and made sure that mature cow size didn’t get too out of hand,” he summarizes. “The point is, all these traits are moderate to high in heritability, a proper and intended breeding program that addresses mature size relative to growth can be accomplished.”
