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A Strategy for Culling Cows

Extended drought caused Nancy and Rex Peterson to downsize their beef herd from 340 to 275 head. Due to their detailed, computerized record-keeping system, the Gordon, Nebraska, ranchers were able to make the heavy cut, confident they were culling the least-productive cows and those with the greatest potential for health or performance problems.

“By culling deeply, we’ve been able to move the bottom end of the herd up a couple of notches in quality and uniformity,” says Nancy Peterson.

Since 1997, Peterson has kept individualized herd records using CowCalf5, a computerized system capable of providing detailed information relating to each cow’s pedigree, health, performance, reproductive history, and performance of progeny.

“The program is designed so I can make the record keeping as detailed or as a simple as I want,” she says.

Based on individual lifetime and performance information Peterson keys in, it displays, for instance, a cow’s average calving date, weaning weights of the calves, an udder score, body weight at the time of pregnancy checking, health status, and calves’ feedlot performance and carcass data.

All data categories include a herd ratio, which shows how an individual animal ranks in the herd. A ratio of 100 means a cow is average for a particular trait. Lower than 100 is below average; higher than 100 is above average.

When using the individualized data to make culling decisions, Peterson focuses on the traits they’ve identified as being most critical to their individual operation. 

“We want to produce calves that gain well in the feedlot and have good carcass data,” she explains. “So if I have a cow that has a good MPPA [most probable producing ability] of 102, but her calves perform poorly in the feedlot or have below-average rib eyes, I’ll get rid of her.”

In years when a normal amount of forage production allows the cow herd to remain at a constant number, the Petersons’ average annual culling rate is 15% of the cows with calves. The culled cows are replaced with the best of the bred heifers the couple retain annually.

As a rule, five primary criteria decide which females will be cut.

1. Pregnancy Status
Any cows turning up open at fall preg-checking time automatically make the cull list. “In a normal year, we have a pregnancy rate between 93% and 95%,” says Peterson.

2. Age
“Longevity is really valuable to have in a cow,” she says. “The longer she lives, the fewer heifers it takes to replace her.” For that reason, Peterson does not set a specific age as an automatic cutoff time for a cow to leave the herd. Rather, she watches weaning weights of aging cows’ calves. A weaning weight lighter than average for an individual cow alerts her to look at the calf’s birth date to see if it’s younger than normal.

“If the birth date of the calf is not the problem, I have to assume the cow is not as productive as she used to be, and that it’s time to cull her,” she says.

3. Physical Status
In evaluating physical condition, Peterson considers factors that could contribute to serious health and performance challenges for a cow in the upcoming production year. She considers, for instance, soundness of legs, feet, and teeth, along with thriftiness of body condition.

4. Production
Peterson considers the weaning weight of an individual cow’s calf and pays attention to a cow’s herd index. She tempers this with a visual appraisal of cow condition.

Her goal is to strike a balance between traits. She wants a cow to milk well enough to produce a calf weight with a reasonably high herd ratio, but she also wants the cow to do the work of raising a good calf without sacrificing body condition and the ability to rebreed in good time.

“Because we live in a semiarid region where drought is an ever-present danger, I don’t want cows that milk overly much,” says Peterson. “In a drought year, when grass is reduced, cows that milk a lot might not breed back.”

Additional considerations Peterson balances against calf-weaning weight when evaluating a cow’s production record include the backgrounding and feedlot performance of the calf, along with its carcass data.

5 Udder Score
Peterson assigns each cow an udder score, which identifies cows with unbalanced quarters, poor udder attachment, or excessively large or misshapen teats. These conditions can lead to diseases such as mastitis and often make it difficult for the calf to nurse, challenging its ability to get colostrum soon after birth.

Regularly culling cows with poor udder scores reduces disease problems in both cow and calf.

This is particularly important to the Petersons, because their cows calve in spring on highly nutritious rye pastures. The top-quality forage promotes good milk production, which calves must be able to consume readily in order to sustain udder health in the dams.

Over the course of the last year, as worsening drought caused the Petersons to cull cows more heavily than in a normal year, they made the more stringent selection by relying on the selection criteria guiding herd improvement over the long term.

“You have to decide which traits are important to you and then measure them,” says Peterson. “You can’t change a trait if you don’t measure it. Then you have to have a way to recover the measured data and use it to improve the herd.” 

To learn more, contact Nancy Peterson at 308-282-0880 or email at

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