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Efficient cow size depends on biological and economic metrics

by Wyoming Livestock Roundup

Cow size is a heavily debated topic at coffee tables, sale yards and calving barns, with no solid consensus throughout the industry. Dr. Dustin Aherin, vice president of Rabo Research Animal Protein Analyst discusses how cow size translates into profitability during the Cattle U and Trade Show hosted by the High Plains Journal.  

Previous literature, Aherin shares, has found smaller-framed, lighter milking cows to be more economically efficient and profitable, while other studies found increased profitability with larger and/or heavier milking cows. While the studies differ in economic method, resource condition and geography, the greatest differences between the studies are in metrics used to measure efficiency. 

Cow efficiency from a per dollar basis, per head basis or a per acre basis are all important to consider when thinking about efficiency, says Aherin. The basis used to measure efficiency depends on the goals of the operation. 

Biological versus economic efficiency

“Biological efficiency and economic efficiency are not the same thing,” Aherin states. “Although both metrics are important, they depend a lot on the specific conditions measured, and it is important to measure them separately.” 

Often, biological efficiency and economic efficiency align fairy well, says Aherin. But, this is certainly not always the case, and there are several studies showing the different rankings of biological efficiency and economic efficiency. 

“Cow efficiency is a key point the beef industry needs to address, as the cowherd accounts for roughly 50 percent of total energy consumption in beef production,” he notes. “We need to figure out how cattle can consume energy efficiently from a biological standpoint in terms of the number of calves or the pounds of calf weaned, as well as the economic efficiency, such as the cost of energy.” 

Before digging too deep into the details, it’s easy to see  one size does not fit all, says Aherin. Ideal cow size for efficiency and profitability depends on operation goals, geography, management practices and marketing strategies, at the least. 

Modeling cow size and efficiency

In his doctoral dissertation, Aherin created a model to quantify the biological and economic efficiency of cow/calf production with varying combinations of mature cow weight and peak lactation in the Flint Hills of Kansas. The model worked to combine genetic potential, growth impacts, reproductive and nutritive requirements and overall cow health. 

In the study, kilograms weaned per cow exposed increased with mature cow size, which Aherin explains as a known correlation between calf growth and cow size. Kilograms weaned per cow also increased with increases in milk and lactation. 

Both metrics, as seen from a biological standpoint, suggest there might not be enough added weaning weight from large mature cows to offset their nutrient requirements when considering energy intake relative to calf weaning weight, Aherin says. 

From a peak lactation standpoint, Aherin’s study found higher lactating cows were more efficient, but he explains this metric varies depending on nutrient availability, herd management and herd uniformity. Lack of uniformity can lead to discrepancies in both research and real-world production.

“The underlying theme is the importance of having a uniform cowherd and managing on a uniform basis,” Aherin notes. “If a producer’s cowherd is not uniform, some cows are going to be getting too much nutrition, while others won’t be getting enough.” 

Economic efficiency

From an economic standpoint, data from Aherin’s study suggests as cow size decreases, return per cow exposed tends to increase also. The trend continues with lactation, but is less apparent in heavy weight cows due to the interaction between nutritional requirements and dollar return. 

“Looking at return on a per head basis, it depends on economic conditions,” Aherin says. “On an individual year basis, when feed is cheap and cattle prices are high, larger cows are favored because producers will see greater return on a per head basis. On the other hand, when feed prices are high, bigger cows will lose the most money.” 

He notes smaller cows tend to be more stable in terms of general return per animal. On a lactation basis, results were similar. 

“When feed costs are cheap relative to cattle prices, producers are rewarded by weaning as many pounds as possible, so heavy milking cows tend to be more profitable on a per head basis,” shares Aherin. “When feed costs are high relative to cattle prices, the advantage goes away.” 

“Perhaps the best metric to look at economic efficiency is return on investment (ROI),” he adds. “With ROI, we tend to see an increase with smaller cows and higher lactation potential.” 

Real-world herd application

However, Aherin notes this model assumed all cow types exist in reality. 

He asks, “How many 1,000-pound cows have a peak lactation of 30 pounds per day in a real beef cow herd?”

Another assumption his model made was no price differentiation based on projected performance after weaning.  

“A different study which looked at calf projected performance suggests a $5.98 per hundredweight (cwt) discount between a small-framed calf and a medium-framed calf,” says Aherin. “It is safe to assume 1,000-pound cows could end up with calves falling in the small-framed category.” 

Although ROI tends to favor smaller to moderate cow weights with heavy lactation, removing assumption of heavy-milking, light weight cows existing in real beef herds and adding the six dollar discount to animals assumed to finish lighter than the industry standard weight changes the picture. 

“We start to see moderate weight cows with moderate to high milk rise to the top,” Aherin explains. “The median is a 1,300-pound cow milking around 27 pounds per day.” 

Aherin notes in the beef industry, we are often taught to keep a uniform cowherd, maintain body condition scores between a four and a six, keep pregnancy percentages above 90 percent and manage nutrient requirements and cow type to match the environment.

“Following recommended practices and accounting for differences in size at weaning, the most economically efficient cow weighs somewhere between 1,200 and 1,400 pounds, with a peak lactation near 25 pounds per day,” Aherin concludes. 

Averi Hales is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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