A producer has a group of 112 heifers. The heifers were synchronized, and after a 45-day breeding season only 80% were confirmed pregnant.
During a recent “Bovine Science with BCI” podcast, Kansas State University veterinarians Brad White and Bob Larson explore potential causes for the issue — from bull problems to nutritional and health-related factors. They also share practical strategies and management tips producers can implement to improve reproductive success and set the herd up for a better breeding season.
Larson says, while the pregnancy rates weren’t optimal, the results weren’t catastrophic. The first breeding cycle performed well.
Reviewing the pregnancy data they determined:
- 57% of heifers became pregnant in the first 21-day breeding cycle.
After synchronization the heifers were artificially inseminated and then turned out with bulls. Larson says the goal or expectation should be 60% to 65% every 21 days so 57% is not too low. - 39% of remaining heifers got pregnant in the second 21-day cycle.
Larson explains this is the rate that is the biggest problem and concern. - The final breeding period (about four days) added a few more pregnancies.
White explains about those who conceived in the first cycle, “Those heifers kept out of this scenario are going to be great cows for the herd. They’re bred at the right time.”
According to the veterinarians the potential reasons for the less-than-ideal pregnancy rates after the first cycle include:
- Heifer Factors
Heifers were initially developed in a dry lot with a high body condition score (7 out of 9) then moved from dry lot to native range after initial breeding. Larson says the potential body condition loss could have impacted fertility as a negative energy pattern can pause a female’s estrus cycle. - Bull Factors
The producer turned out the 112 heifers with five bulls — three yearlings and two mature bulls. With the conception after the first cycle, the bulls had approximately 48 heifers to service. Larson explains the biggest concern is the synchronization created a concentrated breeding period and the bulls might have struggled with multiple heifers in heat simultaneously. Another fertility consideration is social dynamics and breeding behavior.
“The only solution I have for that is more bull power,” Larson says. “And that can get expensive, really fast, when you think about dollars per pregnancy during that second 21 days, when you know 60% of them are already pregnant.”
After reviewing the case, Larson gave these recommendations to the producer:
- Target and maintain heifer body condition score around 6 (not 7)
- Avoid significant body condition changes during early pregnancy
- Carefully time movement from dry lot to pasture
- Consider smaller heifer groups
- Potentially rotate bulls between groups
- Explore heat detection and re-breeding options
- Evaluate bull power and allocation strategies
The discussion highlights the complexity of heifer breeding, emphasizing that multiple factors can influence pregnancy rates. Larson summarizes careful observation, strategic management and understanding the biological and social dynamics of the herd are crucial to improve reproductive success.
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