Double ovsynch has remained one of the best tools to submit cows to first insemination for full timed artificial insemination (FTAI) since its inception. Ultimately, it was the ease of FTAI that made the program popular as heat detection can be a struggle in some modern dairy herds.
Now that estrus detection technology has become more affordable and therefore widely available, researchers have started exploring ways to combine data from automated systems with synchronization programs that optimize fertility and management.
Julio Giordano and Ana Laplacette, a professor and a Ph.D. student at Cornell University, investigated this possibility by studying more than 4,600 cows from two farms. “We want to take advantage of the power of synchronization of ovulation and the power of estrus to get the best of both, synergizing the two,” said Giordano.
The only change to the well-known double ovsynch protocol includes a delay in the final administration of GnRH before breeding. The goal is to allow cows more time to show estrus as previous research suggests potential positive effects of estrus on fertility.
Making more cows show heat
The historical 56-hour gap between the prostaglandin and GnRH treatments before FTAI during the second ovsynch of double ovsynch is backed by years of research and should be respected for optimizing fertility. However, few cows show estrus on this protocol. “There is nothing wrong with the cows who don’t show estrus during the double ovsynch protocol with the 56 hour GnRH. This is supposed to happen,” said Giordano on the “Dairy Science Digest” podcast. “Commonly, very few cows (less than 5%) are bred in estrus before FTAI in double ovsynch.”
As researchers noticed that cows that show estrus at the end of synchronization programs had better fertility, they started exploring ways to breed more cows in estrus and help more cows show estrus before FTAI. To make this happen, they look at their previous research. “The peak of automated estrus activity onset is 60 to 80 hours after the final prostaglandin of ovsynch programs,” Laplacette described.
By extending the traditional double ovsynch timeline from 56 hours between the second prostaglandin and GnRH to 80 hours, the team expected to let more cows show heat before the FTAI and breed more cows in heat.
Controlling ovarian structures
While it is an oversimplification, all synchronization protocols boil down to controlling the source of estrogen and progesterone to ensure the cow is primed for insemination at a specific time. These hormones are produced by the follicle and corpus luteum (CL), respectively.
Cows in this trial ultimately sorted into three categories:
- Expressed estrus before the final GnRH
- Expressed estrus after the final GnRH
- Received the final GnRH and never expressed estrus (anestrus)
Of the two-thirds of the cows that showed estrus, their follicles were larger before breeding, more cows had uterine tone and fluid, and all of them had a CL, the structure supporting pregnancy, after breeding. “This reflected how optimized the physiology was before breeding for cows that showed estrus and could explain the fantastic fertility results we observed,” Giordano commented.
On the other hand, 13% of the anestrus cows had no CL on their ovaries after FTAI. “No CL, no pregnancy,” he added.
Protocol shift helps identify more fertile cows
Though it was not statistically significant, the team observed a 2% higher conception rate for the cows that didn’t get the second prostaglandin until after 80 hours compared to the cows on the standard schedule (53% versus 51%). However, that’s not the full story.
When comparing the cows that did and didn’t show heat, the 80-hour protocol generated an outstanding 60% conception rate when using sexed and conventional beef semen. That shows the power of estrus combined with synchronization of ovulation. Unfortunately, the cows bringing down the average conception rate for the 80-hour protocol were the cows that didn’t show heat.
Future research is focused on addressing these cows that didn’t show heat and improving their fertility. Meanwhile, we can now manage the high fertility group with confidence as we place sexed semen or embryos in.
Watch for future work out of Cornell University on how to manage the lower fertility yet high producing cows. To learn more about this research, listen in to the monthly podcast, “Dairy Science Digest,” on your favorite podcast platform. The research findings were summarized in a peer-reviewed open access article in the Journal of Dairy Science found at www.journalofdairyscience.org.
