This article was #24 of the Top 25 most well-read articles on www.progressivedairy.com in 2014. It was published in the May 29, 2014 Extra e-newsletter. Michigan State University’s Dr. Richard Pursley promoted an adaptation to Presynch protocols that could increase the chance of pregnancy. By switching from a Presynch-14 to a Presynch-10 or Presynch-11 protocol, improvements can be realized due to enhanced levels of progesterone – the limiting factor in dairy cow fertility.
We asked Pursley,
Q. What management advice do you offer to dairies that are considering switching from Presynch-14 to Presynch-10 or Presynch-11?
Transitioning from Presynch-14 to Presynch-11 or Presynch-10 may seem simple, but as mentioned in the article, the logistics of making this change is anything but simple. Transitioning to Presynch-11 requires the initial PG injections to be administered on the same day that a previously synchronized group is receiving A.I. (for example, moving the PG injections from a Monday to a Thursday). There are only 24hours in the day, so moving tasks from a Monday to a Thursday may also require moving tasks from Thursday to Monday.
In the case of switching to Presynch-11, switching the A.I. task to Monday is out of the question. Thus, this may require more lockup time for cows in addition to more thinking time for the humans. Excessive multitasking may result in making more mistakes in addition to taking longer to complete tasks. Switching to Presynch-10 (example, moving initial PG injections from Monday to Friday) may be more manageable.
—Dr. Richard Pursley, Michigan State University
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A few little tweaks to the Presynch/Ovsynch program is helping some dairies improve conception rates and, ultimately, profits.
According to Michigan State University’s J. Richard Pursley, changing from a Presynch-14 to Presynch-10 or 11 protocol can have a positive impact on fertility due to enhanced progesterone levels, which correlate to greater chance of pregnancy.
Progesterone has been identified as a key limiting factor in dairy cow fertility. Pursley’s research indicates that greater concentrations of the hormone are important during the week prior to the final prostaglandin shot of Ovsynch, which is also the growth phase of the follicle.
Cows need to be on Day 6 or 7 of the estrus cycle when they receive the first GnRH injection of Ovsynch. This timing gives them the best chance of ovulating a follicle. That estrogen-producing follicle turns into a corpus luteum (CL) with elevated progresterone levels seven days later.
With this in mind, Pursley explains that the best outcome for a Presynch/Ovsynch program is for the cow to be on day six or seven when the first GnRH of Ovsynch is administered. That means the cow will receive the second of two Presynch prostaglandin injections 10 or 11 days prior to the start of Ovsynch. This differs from the classic approach of receiving prostaglandin 14 days prior Ovsynch, known as Presynch-14.
Just how much of a difference can three or four days make? Data shows that cows have as much as an 80 percent chance of ovulation at first GnRH with Presynch-11, compared to a 40 percent chance of ovulation with Presynch-14. In other words, 100 percent more cows will have a new, growing CL that will enhance progesterone and have ovulatory follicles of a more ideal age and size, thus increasing the chance of pregnancy.
Switching from Presynch-14 to Presynch-10 or 11 may be easier said than done, but outcomes can be successful with a mindset shift and adherence to protocol.
If the GnRH and prostaglandin of Ovsynch are given on Mondays, the two prostaglandin Presynch injections would move to Thursday or Friday. Because Thursday is often the dairy of A.I., managers will need to make an adjustment. All first A.I. cows on Presynch-10 or 11 must finish the program and then receive either a timed A.I. breeding or be bred to a detected estrus following the final prostaglandin of Ovsynch. These cows should not be inseminated to a detected estrus following the Presynch injections.
If done correctly and according to protocol, the rewards of this change can be a 50 percent increase in conception rates and a decrease in the number of cows that are reinseminated via detected estrus or Resynch.
Learn more about synchronization programs like Presynch-10 and 11 by watching Pursley’s animated video.
You could also access printable calendars for Presynch-10, 11 and other programs by visiting Michigan State University's bovine reproduction resource guide. PD
PHOTO
Photo by Fredric Ridenour.
