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Serving: IA
Beefs and Beliefs

Big ol' heifers make big ol' cows

cattle in pasture
Feeding heifers to get them bred makes sense, but the costs are higher than just the feed they eat.

When we talk about feeding heifers to get them bred we usually think it's just a little feed. But the consequences are much larger, more expensive and longer-lasting.

The truth is that big ol' heifers come from and make more of big ol' cows. Those big cows eat a lot more pasture and need a lot more supplement and hay and produce less pounds of beef with those higher inputs. Those inputs cost money and it adds up over time.

In the June edition of Beef Producer I gave the example, using NRC data, of the energy needs of a 1,400-pound cow versus a 1,000-pound cow in a warm-season, native-range environment.

It was a review of the knowledge that smaller cows have lower nutrient requirements and lower maintenance costs. It should be well-known by now, but apparently isn't.

It's being born out in research trials now, and has been argued for many years by those producers who have actually chosen smaller animals.

Using data from NRC and multiple range nutritionists, that bigger cow is 1.29 animal units while the 1,000-pound cow is the standard, 1.0 animal unit. That means you can run only 78% as many large cows as small cows. Put simply, on a ranch that can carry 1,000 animal units, that means you would run about 780 big cows versus 1,000 small cows.

A University of Wyoming study recently showed over several years a 5,500-acre ranch could carry 237 such smaller cows versus 186 similarly larger cows. Those smaller cows averaged 24,251 pounds more calf weight each year.

This and other data also has shown us you can often wean more pounds of calf per acre with the small cows, and do it at lower cost. This is especially true if you stop selecting cows with high milk production.

But there are other factors at work, here. Larger animals, when they are growing, almost always gain faster than smaller animals so we measure the pounds and look at the size and assume they are the most efficient. In some ways, they are. But more important is that some animals within any given frame size are more efficient than others.

Johann Zietsman, the Zimbabwean rancher and consultant, reminds us the most important denominator to achieve reproduction is good body condition. That good body condition is tied to more than just the amount an animal can eat and how much maintenance costs it has, however.

Zietsman says that appetite, climatic adaptation, and resistance to parasites and diseases is important, too, in addition to a frame size that allows lower maintenance requirements and more freeboard for reproduction within a given environment. All these things make an animal more efficient and are, in fact, the foundation for high reproductive performance.

In a quote from an article I did with Zietsman a couple years ago, he notes these things are also highly heritable and can be selected for, as well: "If we say fertility is lowly heritable then we say body condition (frame size, climatic adaptation, resistance to parasites/diseases and appetite) is also lowly heritable since it is the major determinant of fertility.

"If body condition was lowly heritable then 'survival of the fittest' would not apply and selection for adaptation would be impossible."

So, there are a couple of points I'm trying to make here:

1. Those smaller and better-suited animals are more efficient in a natural environment, both in the amount of groceries they require and how they use the nutrients, but also in how well they reproduce. I have never seen any data on whether smaller, environmentally suited heifers still need that 55-65% of mature weight, but it probably doesn't matter, because if they have been selected for their environment they will be ready for breeding season anyway.

2. If you select big heifers and feed them significant amounts of feed to get them pregnant, you are by default selecting big cows that will need the same thing. Again borrowing data I got from Dave Lalman at Oklahoma State University, and from researchers at the USDA Meat Animal Research Center, the genetic trend for mature weights in Angus cattle, which make up something like 80% or more of the national herd, has been rising for years. Measured mature frame size has stopped, however. This says even though we may have stopped jacking up the frame score on our range cattle, we're now working feverishly to put more muscle in them.

Ultimately, I'm arguing we need to stop breeding and selecting cattle for pieces and select them on the ability to thrive in their own environment and reproduce at a high rate. Further, bringing home bulls that don't fit those requirements still selects for the wrong cows, since most people keep their own replacement heifers.

TAGS: Reproduction
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