UNL experts examine causes of reproductive failure in cattle
In a Dec. 1, 2025 University of Nebraska-Lincoln (UNL) BeefWatch article titled “Why Do I Have So Many Open Cows? Causes of Reproductive Failure,” Nebraska Extension Educator Bethany Johnston and Nebraska Extension Beef Cattle Reproductive Physiologist Rick Funston discuss common factors influencing breed-up rates in cattle herds.
The authors delve further into the subject in a corresponding Dec. 23, 2025 episode of the BeefWatch podcast of the same title, hosted by Nebraska Extension Educator Aaron Berger.
Nutrition considerations
According to the specialists, inadequate nutrition is normally the biggest cause of reproductive failure.
UNL Beef and Forage Specialist Mary Drewnoski refers to nutrition as the “bricks” of building whole animal health. Protein and energy are the most important considerations.
“If you think of building a wall, nutrition is the bricks. If the bricks are missing, the wall is going to fail,” says Drewnoski. “Protein or energy are usually the big rocks missing, especially in young animals which may still be growing.”
To ensure healthy animals throughout gestation, Johnston and Funston agree cows and heifers should be fed on an increasing plane of nutrition during the breeding season.
Additionally, the authors emphasize the time frame in which producers decide to breed their herd has a direct correlation to nutrition.
“When we’re breeding has a huge impact on level of nutrition,” emphasizes Funston. “The best quality forage is going to be early in the breeding season, not later.”
Nutrient deficiency can be addressed through supplementation of protein and energy during breeding season.
Additionally, the authors remind producers to be wary of declining nutrition in wet years with an abundance of rainfall and increased growth of mature grass.
Since mature grass is lower in protein and energy, pregnant cattle on pasture may benefit from supplements even when there is a lot of grass to go around.
Body condition
Thin cows with body condition scores of four or lower are less likely to breed back, according to Johnston and Funston’s research.
Thin cows also require more energy and protein to gain weight during breeding and lactation and may have a difficult time maintaining health in some range conditions.
“If you have thin cows, you want them to be gaining weight through the breeding season,” says Johnston. “If she’s thin or losing weight, the environment is saying there are not enough nutrients for her to take care of herself.”
Young heifers and cows are still growing, which means they require more protein and energy and should be managed differently than older cows.
Additionally, the authors note a consistent amount of open, young animals could indicate a producer’s environment and genetics are not aligned and management practices may need to be reevaluated.
Bull factors
Effective bull management is equally important to ensuring higher breed-up rates. Providing the proper bull-to-female ratio and monitoring for soundness throughout the entire breeding season can help improve breeding rates.
“Recommendations for
the cow-to-bull ratio depends on the age of the bulls, terrain, size of the pasture and other variables,” write Johnston and Funston. “For older bulls, 25 cows per one bull is suggested. For a yearling bull, the number of females is equal to the bull’s age in months. For example, a 15-month-old bull could run with 15 females.”
Additionally, the authors recommend testing bulls four to six weeks prior to turnout, emphasizing since sperm production is a 61-day process, breeding tests conducted too early may fail to detect issues and injuries affecting breeding rate.
Further, the authors say bulls should be monitored for soundness issues and swelling – especially around the sheath and scrotal areas – throughout the breeding season, rather than solely relying upon the breeding soundness exam (BSE).
Infections and preg checking
If cattle are still coming up open in cases where nutrition deficiencies have been ruled out, producers may look towards investigating potential infections.
Johnston and Funston note working with a local veterinarian to determine if disease is present and working out a corresponding vaccination plan is the best course of action.
The authors also recommend testing non-virgin bulls for trichomoniasis during BSEs, as the disease can have detrimental effects on breed-up rates.
Additionally, taking care while conducting preg checking and artificial insemination (AI) is vital.
Funston recommends waiting to preg check until after 50 days of breeding to reduce the amount of embryonic loss in pregnant animals.
Additionally, in cases of AI breeding, moving animals either within five days of insemination or waiting 45 days after breeding can help protect small, fragile embryos and reduce risk of embryonic loss.
Other considerations
In closing, Johnston and Funston emphasize implementing good management practices, prioritizing nutrition, monitoring bull performance and eliminating infections should result in pregnancy rates of 90 percent or greater in cows and 80 percent or greater in heifers.
If pregnancy rates remain significantly lower, the authors encourage producers to contact their local veterinarian.
A list of questions including whether anything changed drastically during the breeding season, if there was drought or overgrazing of pastures, length of the breeding season, timing of the calving window, whether hay and feed was tested and if herds were supplemented with extra protein and energy can help guide conversations, hopefully leading to answers and an improved breed back next season.
Grace Skavdahl is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
