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Beef Reproduction Requires Managing the Details

Reproduction is often called the most important element for cow-calf operations – because without a successful breeding...

Reproduction is often called the most important element for cow-calf operations – because without a successful breeding program there is no live calf to sell.

In early December, Colorado State University hosted its bi-annual Robert E. Taylor Memorial Symposium with the focus of this year’s program on improving the understanding and application of reproductive technologies, including AI, estrus synchronization and factors affecting male fertility.

Over 20 speakers were featured on the two-day program. Following are highlights from some of the presentations. Audio, power point and summary write-ups of all of the speakers can be found online at the newsroom at

As we move into calving season for most Midwestern cow-calf operations, Rick Funston, University of Nebraska Extension reproductive physiologist, reminded participants of the importance nutrition plays on reproductive performance.

Funston said that research indicates, “It is better to have cows and heifers in good condition before calving than to play catch up after calving.” He recommended that cows be in a body condition score (BCS) of 5 to 6 prior to calving.

To that end, he said, “Balanced nutrition is the key to optimizing production.” On his list of nutrients to consider were protein, energy, minerals, vitamins and water. Some tips that he highlighted to achieve this balance:

  • Minerals and vitamins must be balanced in the diet to optimize reproductive performance. Funston recommended that mineral supplementation is critical 45 days prior to calving, through the breeding season and prior to weaning.
  • Consider water quantity and quality when balancing diets.
  • Be cautious about overfeeding nutrients as it has been shown to delay puberty, lower ovulation and lower conception. However, Funston acknowledged that there is a misnomer that feeding cows protein too extensively prior to calving increases dystocia. But he says research has proven otherwise. “It may increase the birth weight slightly, but there is no impact on calving difficulty.” To avoid overfeeding, he reiterates that the rule of thumb for a herd should be a BCS of 5-6 prior to calving.
  • Consider feeding fat as a prepartum supplement. Funston reported on multiple research studies that indicate feeding fat – from sources such as sunflowers to ethanol by-products – about 60 days before calving can improve pregnancy rates in beef cow herds.

Lastly, Funston emphasized that there is no quick fix for reproduction challenges brought on by poor nutrition. He said, “There is no magic feed ingredient that exists to compensate for a diet deficient in any of the mentioned nutrients or poor BCS.”

Jim Graham of Colorado State University emphasized that cow-calf producers should take heed of Breeding Soundness Exams (BSE) and the information they provide to evaluate bull fertility prior to breeding season next spring. He says all three components of the BSE – the physical exam, the health evaluation and the semen analysis – are important.

Graham suggests that producers should cull the bulls that fall in the lowest 15-20% of the BSE exam. “Remember the most important thing is fertility and getting cows bred,” he says. Thus, culling bulls based on BSE results such as a small scrotal circumference or low motility is a step toward improving herd fertility. “This is a very cost-effective approach,” Graham adds.

Graham also discussed the status of sexed semen in cattle. He explains that the only way to sex semen reliably is based on the different DNA composition of the X and Y chromosomes – the X chromosome is 3.8% larger than the Y. “That’s not very much,” Graham says.

While the sexing process does produce safe, viable sperm and calves, Graham reports that sorted sperm are very different than non-sorted due to the pressure of going through the flow cytometer. “Sex sorted cells swim differently; die more quickly and have more damage,” he says.

Because of the fertility differences in bulls, he adds that semen from some bulls cannot be sorted. “Some don’t take the stain through the sorting process or because of the added damage to the cells after sorting, they won’t freeze.”

Thus, Graham believes sexed semen will likely continue to be available only in small numbers.

George Perry, assistant professor in beef reproductive management at South Dakota State University, addressed the question of why beef herd pregnancy rates can vary so much.

He attributes the variation to management, saying, “Management can affect the outcome of artificial insemination (A.I.) or natural service breeding.” And he emphasizes to cow-calf producers, “Little mistakes can add up to a big impact on fertility.”

Specifically, Perry says the reproduction equation includes the following key areas:

1. Animals detected in heat and inseminated.
2. Inseminator efficiency.
3. Fertility level of the herd.
4. Semen fertility level.

Perry says if producers were perfect in each of those four areas (i.e. achieving 100%) they could have 100% fertility. However, if they only achieve 70% in each of those areas, herd fertility can be significantly reduced.

In reviewing the four key areas that he outlined, Perry reminds producers that success is in the details. For instance, regarding estrous detection, he says, “Successful insemination requires animals be detected in standing estrus and inseminated at the correct time.” This is true whether you are using natural service or a synchronization protocol – even fixed time A.I., he adds.

Thus, Perry acknowledges that even with the tools and synchronization protocols available, estrus detection is still essential and it takes a great deal of time and labor, particularly because there are often variations in cattle showing signs of heat, and even animals that may stand in heat, but do not ovulate.

Regarding the second key component of inseminator efficiency, Perry explains that the correct place for semen to be deposited is in the uterine body. If this is done, studies show fertilization occurs 95% of the time. Studies have shown that there is typically a 10% reduction in fertility when the semen is deposited in the cervix.

While producers may think they do not need to be concerned with this point if breeding natural service with bulls, Perry says it still should be considered. He says that just because a bull has passed a breeding soundness exam (BSE) does not mean he is physically able to breed cows. In fact, one study showed that 4% of bulls that pass a BSE were not able to physically breed a cow.

Perry emphasizes that bulls should be monitored after being turned out for breeding with the cowherd. As well, producers must consider the appropriate male-to-female ratio or serving capacity. Perry says recommendations range from 1:10 or 1:60. But he says producers should keep in mind these guidelines:

  • Yearling bulls have a lower serving capacity than older bulls.
  • Synchronization places greater pressure on bulls and lowers serving capacity. He recommends about a 1:20 or 1:25 ratio in these instances.
  • Multiple sire pastures decrease serving capacity since multiple sires will mate a individual cow.

As a third point, Perry says cow-calf producers must consider the fertility level of their herd, which can be influenced by many factors such as herd health, nutrition and body condition, and stress.

Perry acknowledges that some embryonic death is unavoidable and is a means of eliminating unfit genotypes. But he cautions that stress due to shipping, heat or even running cattle through chutes can delay embryo development.

Lastly, Perry says producers must be aware that there can also be differences in fertility levels of semen, and this too can reduce fertility rates. To maximize chances for fertilization, he says it goes back to watching the details such as heat detection and correct placement of the semen within the female at ovulation.

Perry concludes, “Producers must recognize that all of the management decisions that are made through the year add up to what occurs during the breeding season. Producers must think about everything they do that can affect their herd’s reproductive performance.”

Hear what additional speakers had to say about DNA technology and other reproductive topics by going to and clicking on newsroom.