That’s the recommendation of a recent interdisciplinary study involving rangeland researchers in Oregon, Wyoming and Oklahoma. Breeding smaller cattle could be a long-term strategy that will help ranchers and ease pressure on an increasingly drought-prone range, said Leticia Henderson, a livestock and range extension agent at Oregon State University.
The research team developed a statistical model that showed smaller cows have distinct advantages over larger ones in pastures where the cows don’t have much to chew on.
The study is published in the journal Rangelands. It is meant to help cattle producers develop long-term strategies on cattle selection and natural resource management for areas in the U.S. that are expected to experience more frequent and severe droughts. Cattle ranchers have coped with drought by reducing the size of their herds or increasing their feed, but these methods are costly and don’t solve the problem in the long run, Henderson said.
If the total herd size is larger – 100 head weighing 1,000 pounds versus 78 head weighing 1,400 pounds – feed costs will be lower. Also, with all things being equal in a pasture with little to graze, a smaller cow can produce milk more quickly because it doesn’t expend as much energy to maintain its body size.
“The perceived benefit of larger cows is that they will be able to produce larger calves,” Henderson said. “But the smallest cow size in our model was the most efficient at weaning. That’s based on a previous study by our group that found larger cows in nutrient-limited rangelands don’t always wean larger calves.”
Grazed forage remains the least expensive source of nutrients to maintain the cow herd, Henderson said, so matching cow size and milk production potential to forage resources should help mitigate the effects of rangeland drought on the herd.
The researchers assumed cows in limited-nutrient environments would eat 2.2 percent of their bodyweight daily over a 210-day weaning period. An ideal weaned calf should weigh about half as much as its mother, “so the likelihood of a 1,400-pound cow weaning a 700-pound calf on rangeland is highly unlikely in 210 days,” Henderson said.
Recent studies suggest the ideal cow weighs between 1,000 and 1,200 pounds on land where grazing opportunities are scarce – yet the USDA has determined that the average domestic cow size is nearly 1,400 pounds. The model developed by the researchers used cow sizes ranging from 1,000 pounds to 1,400 pounds.
The increase in the average cow size is the result of a steady trend in selective breeding over the last few decades, and the researchers don’t expect herds of smaller cows in the next few years. They want their model to be considered by cattle ranchers over the long haul, she said.
“This isn’t a short-term solution,” she said. “It took a long time to breed 1,400-pound cows. We’re not going to get down to 1,100-pound cows overnight, either.”
The USDA National Institute of Food and Agriculture funded the research. Derek Scasta, extension rangeland specialist at the University of Wyoming, led the study. 
This article was originally published by Oregon State University Extension Service.
PHOTO: Running cattle on a ranch in sagebrush habitat. Photo courtesy of Oregon State University.
