Experts share how beef cow size, heavier carcasses influence beef at K-State’s Cattlemen’s Day 

Kansas State University’s Emma Briggs, a beef systems specialist, and Mindy King, an assistant professor in animal sciences and industry, discussed beef cow size and heavier carcass weights and their implications for the cow herd and feedlot performance at the recent Cattlemen’s Day in Manhattan.  

Briggs, who is based at the KSU Agricultural Research Center in Hays, Kansas, told attendees she’s passionate about mature cow efficiency and finding those differences to help cattle producers. Many ranchers struggle with how to get cow efficiency to match beef industry expectations.  

“There’s a lot of considerations to look at, especially when we’re talking about cow size considerations and cow efficiency considerations,” she said. “We’ve been using cow size as a proxy of body weight for a proxy of intake. And we’ve been doing this for a long time. Why?” 

Measuring forage intake on cattle in a pasture is difficult, Briggs said, and scientists at K-State and other universities realize it takes a long time to try to estimate dry matter intake on forage—and it takes a lot of fecal sampling, which takes time. 

“In order to make genetic change, using a proxy trait like body weight for dry matter intake, we know that trait has to be heritable, and there has to be a genetic correlation between the two traits.” 

Measuring essential

Body weight is easier to measure, and sending those cows across the scale can give needed information instantly. 

Post-weaning growth needs to be paid attention to, according to Briggs, because as those inherent increases occur, those calves head off to the feed yard.  

“It’s no surprise. We’ve been beating this like a dead horse. Our cows are getting bigger,” Briggs said. “The days of 1,000-to-1,100-pound cow, in some scenarios, is almost gone.” 

She’s a big believer in collecting data and using it to make choices. The same goes for tracking carcass trends. Cow weights can be used as an estimate to see how many cows to run based on what they normally eat. Typically, cows eat 2.5% of their body weight. 

For example, when comparing a 1,250-pound cow to a 1,500-pounder, there is about a 13% difference in their daily dry matter intake. That is about a 15-cow difference in stocking rate in certain conditions. 

The question becomes, can a rancher’s 1,500-pound cow produce enough pounds of weaning weight to make up for the 15-cow deficit, she said,  

Industry responds

The beef industry has been effective in posting weaning efficiencies in terms of heavier calves coming off the cow by using expected progeny differences and genetic selection.  

All of the calculators and tools are used to evaluate animals that are consuming an energy dense diet. “There’s not a lot of whole herd reporting for these breed associations that take place with growing animals consuming the forage-based diet,” she said. 

Briggs questions the current tools that are readily available to evaluate post weaning efficiency for cows that go out and graze, but differences remain. There are two kinds of mechanisms that regulate intake—chemostatic being one of them. 

“We talk about animals that have different pathways that tell the animal ‘you’ve had enough you can stop eating,’” she said. “But when you’re talking about cattle that are on a moderate-to low-quality forage diet, it’s mainly the rumen stretch that tells the animal to stop eating. That’s one of the reasons why we would consider the fact that there are potential differences in intake regulation as a whole, and how that could potentially impact performance.” 

In her study, Briggs looked at two heifers that were similar in their makeup—both artificially inseminated, they were both conceived via timed AI and are high performing, but they did differ phenotypically though. 

“Now we had these animals consuming a moderate quality hay, forage only. Nothing but hay, water and mineral for them, for about 72 days, and then we transitioned them into a mixed diet,” she said. “We’re going to call that a TMR diet. It was basically 50% hay, 50% concentrate, and what I saw physically, they were gaining about the same.” 

Both cows were gaining “just a hair under a pound per head per day,” while eating the forage. But one heifer was eating 13 pounds of dry matter of forage to get a pound of gain, while the other was eating 16 pounds. 

“If we look at that over the course of a year, roughly, that’s almost one round bale of feed differences per year, or throughout a year in forage intake differences,” she said. “And what was really more interesting, if we look at them when they were in that TMR segment, we saw also a very similar process. Those heifers gaining about the same on this energy dense diet, but they also had a very different dry matter intake in order to get to the same amount of phenotypic gain that we saw with them.” 

Briggs said even though these two heifers look the same and gain relatively the same, there are still metabolic differences. When they became 4 years old, she collected mature cow weights on them. and they ended up being bigger than “our standard 1,200-pound cow.” 

“Their mature weights are about the same. They’re about the same frame height. They perform really well, almost identical cows within themselves,” she said. “But it’s important to figure out, and then we come to this conclusion of 74% of the feed energy in order to produce 1 pound of carcass weight comes from the cow-calf sector alone, which means that we have a really high responsibility in the cow-calf sector to make sure that we have improved efficiency and profitability, because it’s going to transfer over for the rest of the industry.” 

Matching your environment

Briggs said the important key is to find animals that are metabolically efficient and divergent from each other. It’s also important to match genetic potential with the environment.  

“It’s about finding animals that match your environment,” she said. “And so we come back to this question of cow size and how many cows that we can run on a piece of property. So, the question is, what is seven calves worth to you?” 

But the next question needs to be “is this always correct?” she said.  

“Cow size alone, though it’s a really good proxy for what we have, does not evaluate metabolic efficiency in its entirety, and it doesn’t tell us a lot about how those animals utilize that forage in order to produce measurable outputs,” she said. 

Cows need resources to be able to reach genetic potential and the types of cattle that match environment and management are part of what makes them efficient cows later on. Some things that possibly make efficient cows include—maintenance, energy requirements, cow size, milk production, fertility, skeletal structure, udder structure, she said.  

“And I would argue to say that it’s all of those things combined, and it’s about creating a cow that works for you,” she said.  

Looking into the future is full of unknowns, and Briggs said to rely on what you do know—cow size can be a proxy for dry matter intake. There’s always exceptions to the rule though.  

“As an industry, we need to find what makes the exceptions to the rule more apparent,” she said. “Larger cows could potentially have an increase in energy needs. But metabolic efficiency in selecting for cows that have increased forage utilization and nutrient utilization is going to be key in order to create animals that can perform in this environment.” 

Kylene Scott can be reached at 620-227-1804 or [email protected].