When it comes to measuring the success of fixed-time artificial insemination (FTAI), Cliff Lamb, assistant director of the North Florida Research and Education Center (NFREC) says, “I’m not so sure that pregnancy rate to AI is all that important. …âMy goal is the percentage of cows that become pregnant in the first 30 days of the breeding season. That is probably the most important economic indicator we have in our operation.”
The NFREC is a research and education campus for the University of Florida. It runs its cow herd as a commercial operation, but shifted from breeding cows with natural service to FTAI, giving every female the opportunity to become pregnant through AI.
Overall, season-ending pregnancy rates were 81% to 86% before they started synchronizing and using FTAI seven years ago. Those rates are 92% to 94% the past three years. Each year, the calving season gets shorter.
“In five years, we’ve essentially gone down from 120-day breeding season to a 70-day season, and all cows are eligible to be artificially inseminated on the first day of breeding season,” Lamb explains.
More than the technology, the NFREC underscores the importance of establishing and adhering to realistic management and selection criteria, relative to the goals, environment and resources of each operation. These are the rules Lamb established and has stuck to for the past seven breeding seasons:
• Every cow will calve by the time she is 24 months of age.
• Every cow must have a calf every 365 days.
• Every cow must calve without assistance.
• Cows must provide sufficient resources for the calf to express its genetic potential.
• Calves must be genetically capable to perform.
• Cows must maintain their body condition score in their ranch conditions.
• Cows must not be crazy (disposition).
Plus, heifers must be bred within 25 days to remain in the herd. The NFREC preg-checks 28 days after the 25th day of breeding. Lamb allows that there has been more than one conversation over the years about culling a keeping-quality heifer that bred on day 26. They don’t waver, though.
“They might become very good animals in someone else’s operation, but in our operation, we want them pregnant earlier,” Lamb says. “I don’t think we’re selecting for fertility. I don’t think we’re selecting for pregnancy. All we’re expecting is those cows to become pregnant in our environment and in our management system.”
Lamb used results from a larger study he was involved with in South Dakota to demonstrate another primary gain from timed AI — increased days between calving and the next breeding season. The study included eight operations and 1,700 cows, synchronized using the seven-day CO-synch plus controlled internal drug release (CIDR) protocol (gonadotropin-releasing hormone [GnRH] and CIDR on day one; CIDR removal and prostaglandin on day 7; GnRH and timed AI on day 10).
Three herds achieved what many would consider to be acceptable first-service pregnancy rates of 56.9% to 65.8%. The other five had rates (44.4% to 50.4%) that many would consider to be disappointing.
For anyone with little FTAI experience, Lamb emphasizes the need for realistic expectations.
“The expectations need to be different for every cattle operation depending on how the cattle are treated from year to year,” Lamb says.
Researchers found only one consistent difference between the herds with higher rates and the others.
“These three herds had all utilized AI for eight years or more consistently, regardless of the pregnancy rates they got the year before,” Lamb explains. “They continued to stay committed to synchronization year after year.”
Lamb compared the calving distribution between herds that had never used AI before with those that used it consistently.
In the bull-bred herds, 44% of the calves were born from the day the first calf arrived to 30 days later. Lamb points out these were well-managed operations with calving seasons of less than 75 days.
The average postpartum interval (PPI) in these herds by the start of the next breeding season was 64 days, on average. There were 43% of cows with less than 50 days PPI at the start of the next breeding season.
In the FTAI herds, 88% of cows calved in the first 30 days of the calving season. The average PPI to the start of the next breeding season was 79 days. Only 7% of the cows were less than 50 days PPI at the start of the next season.
“We’re increasing the days of postpartum — that period of time where they can recover and start their estrus cycle before the next breeding season — by 15 days,” Lamb stresses. “A higher percentage of those cows have the chance to start cycling and become pregnant in the next breeding season. So, anything we can do to front-load the calving season is going to increase our fertility to the next breeding season.”
All told, Lamb explains shifting the NFREC herd to FTAI continues to generate substantial economic return, compared to the natural breeding it was doing before. That’s before considering genetic improvement.
“We’re generating $50,000 more to that operation [about 300 calves annually, valued the same year to year] just by putting pressure on that herd for pregnancy, just by creating rules that we expect every cow in that herd to become pregnant when we want them to become pregnant.”
For the free AI Cowculator app developed by Lamb and his peers, go to the Android or Apple app store. You can listen to Lamb’s presentation here.
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