In a perfect world, all of your cows would be fertile, your reproductive program would be a snap and you could focus your attention on other things.
But, that’s not usually the case.
One solution is to turn to synchronization protocols. About 15 years ago, researchers developed these programs to help address reproductive challenges and increase dairy reproductive performance. These protocols have been adapted and modified over the years, but the intent remains the same: get more cows pregnant so they stay productive and in your herd longer.
Data show overall industry reproductive improvement, with average 21-day pregnancy rates approaching 16 percent, up from about 12 to 14 percent several years ago.
However, even in the best-case scenario, not all cows become pregnant via the first insemination. Upwards of 60 percent of cows may fail to conceive on a given AI service for any number of reasons. Resynchronization protocols are designed to overcome these challenges, but they have also led to plenty of frustration.
New research shows that you can improve resynchronization protocols by better setting up cows for success. In essence, your goal is to reset the estrous cycle.
Timing is critical when it comes to the success or failure of a synchronization or resynchronization protocol.
Original research showed that cows enrolled in a protocol between day five and day 12 of their estrous cycle generally get pregnant more often than cows enrolled earlier or later in their cycles. Newer research is aimed at enrolling cows on day six or seven of the estrous cycle.
For farms on resynchronization protocols, this can be a tough target to hit, depending on how you’ve organized your daily tasks and labor force.
The timing at which the resynchronization protocol is initiated can be quite variable, and depends on when pregnancy exams are conducted, says Todd Bilby, Texas AgriLife extension dairy specialist.
So, for example, if the length of the average cow’s estrous cycle is 23 days, and you want to begin the protocol on day five through nine of her cycle, timing your resynchronization protocol at 28 to 32 days after AI should improve pregnancies per AI.
But, cows don’t read the book.
“Only 10.1 percent of open cows return to heat at 23 days after AI, and only 43.5 percent of them return to heat 20 to 24 days after AI,” explains Bilby. “Therefore, starting a resynchronization protocol based solely on days since previous AI is not likely to be a successful strategy.”
Still, University of Wisconsin researchers have shown that resynchronization protocols can work when the resynchronization protocol was initiated on day 33 after AI. A lot of the success depends on the farm and whether you and your employees are willing to strictly comply with protocols.
Biology at work
Complicating the issue, researchers at the University of Wisconsin theorize that today’s high-producing dairy cows may exhibit a later luteinizing hormone (LH) surge, ovulate a larger follicle and exhibit shorter periods of estrus than lower-producing cows. This has a negative effect on fertility and challenges reproductive programs.
In addition, according to research published in the March 2010 Journal of Dairy Science, lack of exposure to progesterone before spontaneous or GnRH-induced ovulation results in greater risk for short luteal phases.
Presynch your resynch
To overcome these and other issues, research on these protocols continues. Some of the latest studies indicate that just as synchronization programs for first breedings benefit from presynchronization, so do resynchronization protocols. By adapting your protocol, you increase the proportion of cows at the ideal part of their estrous cycle when it’s most beneficial.
For example, during a recent research project in California and Arizona that was reported in the September 2010 Journal of Dairy Science, all cows in the study were checked for pregnancy status 38 days after AI. Open cows were enrolled in one of three treatments. The options included a cosynch-72 protocol, where cows received GnRH, a prostaglandin injection seven days later and timed AI plus another GnRH injection 72 hours later, and a GGPG protocol, where cows received a GnRH injection one week prior to the pregnancy exam and then participated in the cosynch-72 protocol. One-third of the cows were enrolled in the cosynch 72 protocol plus a controlled internal drug release (CIDR) insert for seven days (between the GnRH injection at the open diagnosis and the prostaglandin injection).
Results show that cows presynchronized with GnRH before the start of the resynchronization protocol and those treated with a CIDR insert during the resynchronization protocol had greater pregnancy per AI at 90 days after re-insemination compared with cows receiving only the cosynch-72, notes Bilby.
An economic analysis shows that cows that received the GnRH presynchronization injection or received the CIDR insert had greater economic gains than the cosynch-72 protocol. In fact, the GGPG protocol resulted in gains of $8.90 more per cow.
According to research reported in the December 2010 Journal of Dairy Science, University of Florida scientists followed 1,227 Holstein cows that were presynchronized and completed the ovsynch or cosynch-72 protocols. More than half, or 675 non-pregnant Holstein cows, were resynchronized starting at 34 days after the first AI. During this phase of the experiment, cows received the Ovsynch protocol with or without supplemental progesterone, as an intravaginal insert, from the first GnRH injection to the first prostaglandin injection (five days). Pregnancy diagnoses were performed on days 32 and 60 after AI.
In the end, supplementation with progesterone enhanced fertility during resynchronization in the five-day timed AI protocol, concludes Jose Santos, University of Florida reproduction specialist. In fact, pregnancies per AI increased 7 percentage points with this protocol.
And, in unpublished research, University of Wisconsin researchers have used the double-ovsynch protocol (you administer ovsynch twice, using the first Ovsynch as a presynchronization to the second, or breeding Ovsynch) as a resynch protocol. It resulted in better fertility than a more traditional resynchronization strategy, especially for first-lactation cows (53.8 percent).
“Double ovsynch can be used as a resynchronization procedure to improve fertility at second and later AI,” says Milo Wiltbank, University of Wisconsin professor of reproductive physiology, “however, it produces a longer interval between AI and requires more treatments.” Current resynch research underway at the University of Wisconsin aims to reduce the interval between AI services and improve conception rates to these protocols.
So, there you have it. You can make resynchronization protocols more effective and your herd’s reproduction better. You just need to determine what will work best on your farm.