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Copyright © 2015
Angus Journal

The Little Things Matter

FORT COLLINS, COLO. (Dec. 2, 2008) — Why can beef herd pregnancy rates vary so much? What causes the variation? The answer lies in management, says George Perry, assistant professor in beef reproductive management at South Dakota State University. Perry spoke to attendees of the Robert E. Taylor Memorial Symposium: Applied Reproductive Strategies in Beef Cattle Dec. 2 in Fort Collins.

“Management can affect the outcome of artificial insemination (AI) or natural-service breeding,” Perry commented. “Little mistakes can add up to a big impact on fertility.”

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

Reproductive failure is a major source of economic loss in the beef industry. George Perry, assistant professor in beef reproductive management at SDSU, discussed how management factors influence fertility in both AI and natural-service breeding programs using estrus synchronization.

Perry said if producers were perfect in each of those four areas (achieving 100% success) they could have 100% fertility. However, if they only achieve 70% success in each of those areas, herd fertility can be significantly reduced to a 24% pregnancy rate.

Success in the details

In reviewing the four key areas that he outlined, Perry reminded producers that success is in the details. For instance, he said, “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.

Heat detection aides and synchronization protocols can be useful in the breeding process — even with natural service, Perry said. But, he cited several studies that have used these tools and still had large variations in fertility. Likewise, when using a bull, libido or sex drive can vary, which can compromise the herd’s reproductive performance. Perry emphasized the importance of watching a bull when he is turned out with the cows to make sure he has ample libido.

Even with the tools and synchronization protocols available, estrus detection is essential, Perry acknowledged. 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, inseminator efficiency, Perry explained semen must be deposited in the correct location at the correct time. If this is done, studies show fertilization occurs 95% of the time, he said.

The correct place for semen to be deposited is in the uterine body, Perry explained. Studies have shown that there is typically a 10% reduction in fertility when semen is deposited in the cervix.

Producers may think they do not need to be concerned with this point if breeding natural service with bulls, but Perry said it still should be considered. Just because a bull has passed a breeding soundness exam 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 emphasized again that bulls should be monitored after being turned out with the cow herd for breeding. And producers should consider the appropriate male-to-female ratio or serving capacity. Recommendations range from 1:10 to 1:60, but Perry advised producers keep in mind these guidelines:

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

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

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

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

The Robert E. Taylor Memorial Symposium is conducted by Colorado State University every other year to provide current, research-based information for improving profitability in the beef cattle industry. The ARSBC program was developed by the Beef Cattle Reproduction Task Force to improve understanding and application of reproductive technologies, including AI, estrus synchronization and factors affecting male fertility. In 2008, CSU and the Task Force collaborated to provide the Dec. 2-3 symposium in Fort Collins. To listen to Perry’s presentation, view the accompanying PowerPoint or view other presentations from the symposium, visit the newsroom at

– by Kindra Gordon

Click here for accompanying PowerPoint as a pdf file (1.6 MB).
Click here to listen to the presentation (5.4 MB mp3).

Editor’s Note: This article is available as a news release to redistribute per an agreement between the symposium hosts and Angus Productions Inc. Click here to submit a request for a high-resolution photo of the speaker. For additional information visit the newsroom of