About the Little Things: Consistent Herd Pregnancy

US - Small errors in management can add up to big impacts in herd fertility.
calendar icon 12 December 2008
clock icon 3 minute read
University of South Dakota

That's according to South Dakota Cooperative Extension Beef Reproduction Management Specialist George Perry. Perry presented information on reproduction management on 2 December at a beef symposium in Fort Collins, Colorado.

The Robert E. Taylor Memorial Symposium: Applied Reproductive Strategies in Beef Cattle featured beef scientists from around the U.S.

Audio files of Perry's presentation, along with the accompanying slides, are available at this link: www.appliedreprostrategies.com. At the site, click on "Newsroom" then on the "Management & Nutrition Segment" choice.

Perry sought to help producers understand what causes variation in beef herd pregnancy rates, and he pointed to management.

"It can affect the outcome of artificial insemination (AI) or natural service breeding, and little mistakes can add up to big impacts on fertility," said Perry. "The key areas that make up the reproduction equation are:

  1. Animals detected in heat and inseminated
  2. Inseminator efficiency
  3. Fertility level of the herd, and
  4. Semen fertility levels."
Producers could have 100 percent fertility if they have perfection in each of these areas, said Perry. "But even a small decline in each of these areas can add up to reduced pregnancy rates," he said. "Even if each area were a 70 percent success, it would lead to only a 24 percent rate of pregnancy."

Looking specifically at each key point, Perry said details count. "Successful insemination requires animals be detected in standing estrus and proper timing of insemination," he said. "This is true regardless of natural service or synchronization protocol."

Heat detection aides and synchronization protocols can be helpful, even in non-AI herds, Perry said. "Several studies show these tools can be used and fertility variations were still large," said Perry. "One reason is bull libido, which can vary, and can compromise the herd's reproductive performance."

Watching bulls and ensuring ample libido is important, said Perry. "Even more important is estrus detection, and it takes a great deal of time and labor, in part because cattle vary so much in displaying signs of heat," he said. "Some animals may stand but not ovulate."

Inseminator efficiency connects directly to timing and location, Perry said. "Done properly, with semen deposited in the uterine body, fertilization occurs 95 percent of the time," he said. "Studies prove that there can be as much as a 10 percent reduction in fertility when semen is deposited in the cervix. This is important even in natural service because some bulls that pass breeding soundness exams (BSE) are not able to breed cows."

Here, producers who seek successful breeding are advised to monitor their bulls in cow herds, maintain proper male-to-female ratios, and consider guidelines.

"Yearling bulls have a lower serving capacity than older bulls, and multiple-sire pastures are a good way to decrease serving capacity, since multiple sires will mate with individual cows," Perry said. "Producers should remember that synchronization places greater pressure on bulls and again will lower serving capacity. A one-to-20 or one-to-25 ratio of bulls to cows is best in those instances when a mature fertile bull is used."

Cow-calf producers must consider the fertility level of the herd, and the factors that influence this level. "Herd health, nutrition, body condition, and stress all go into fertility level," said Perry. "Some embryonic death is unavoidable, but stress due to heat, running cattle through chutes, and in shipping, all of which can delay embryo development and can be reduced if not avoided altogether."

Fertility levels of semen are one last place where producers can improve reproduction in a herd. "Watch the details, such as heat detection and correct placement of semen, to maximize your success during breeding season," he said. "All of the decisions must be weighed, so consider everything you do that might play a role in the herd's reproductive performance."


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