timing relative to a synchronized ovulation, lactating dairy cows were bred at zero, eight, 16, 24 or 32 hours relative to G2. All cows ovulated to the second GnRH (G2) by 24 to 32 hours after G2. approximately 24 hours after the protocol’s last GnRH treatment. In the first published experiment using Ovsynch to hormonally synchronize ovulation, lactating cows were submitted to timed A.I. Numerous studies have evaluated “best timing” of hormone treatments and/or A.I. than cows submitted to just a Presynch-Ovsynch protocol (50% vs. Cows that were presynchronized using a Double-Ovsynch protocol had more P/A.I. Newer presynchronization strategies that combine GnRH and PGF2α help increase P/AI to timed A.I. “If you use a Presynch-Ovsynch protocol for 100 percent TAI (timed A.I.) for first service, use a 10- to 12-day interval between the second PGF2α treatment and starting Ovsynch,” said Fricke. increased from 29% for cows submitted to an Ovsynch protocol to 43% for cows submitted to a Presynch-Ovsynch protocol.ĭecreasing the interval between the second PGF2α treatment of Presynch to initiation of Ovsynch from 14 to 11 days increased ovulatory response to the first GnRH treatment and increased P/AI by approximately 7 percentage points when all cows were submitted to timed A.I. When only cycling cows were included in the statistical analysis, P/A.I. The first presynchronization strategy tested used two prostaglandin F2α (PGF2α) treatments administered 14 days apart with the second PGF2α treatment preceding the first gonadotropin-releasing hormone (GnRH) treatment of an Ovsynch protocol by 12 days.

Researchers took this discovery and evaluated presynchronization protocols to improve the success of estrous synchronization. Presynchronization boosts repro performance compared with starting it earlier or later during the estrous cycle. When evaluating Ovsynch performance, researchers discovered that starting the Ovsynch protocol between days five and 12 resulted in more P/A.I. Researchers concluded that estrous detection should be combined with Ovsynch and timed A.I. without estrous detection, days to first A.I. In the first Ovsynch field trial, which used only timed A.I. The original Ovsynch called for three sequential hormonal treatments to control ovarian function. In 1995 when Ovsynch was introduced, dairy producers could increase their cows’ service rate. With high-producing cows, estrous duration is often shorter ovulation may not occur after expressing estrus, ovulation may occur without accompanying estrous behavior and some cows are anovular. The second hurdle involves high-producing cows’ biology. Fortunately, current technologies (e.g., pressure-activated heat mount devices, tail chalking and activity monitoring systems) help overcome this challenge. The first primary hurdle involves humans’ inability to visually detect estrus. based on estrous detection alone will yield poor reproductive performance. However, submitting lactating dairy cows for first A.I. to a detected estrus remains the cornerstone of most dairies’ reproductive management programs. service to maximize the 21-day pregnancy rate.Ī.I. and identify nonpregnant cows and return them to A.I. (P/A.I.).” With multiple programs available, Fricke said it’s important to implement a plan to submit cows for first A.I. “Newer fertility programs increase both service rate and pregnancies per A.I. “Many strategies can be implemented to achieve excellent 21-day pregnancy rates by increasing the A.I. The dairy industry offers a variety of reproductive management programs, including some that synchronize estrus via hormone protocols. Strict protocols to prevent calfhood diseases: Case studyĪt the 2018 Dairy Cattle Reproduction Council annual meeting, Paul Fricke, University of Wisconsin – Madison professor of dairy science and extension specialist in dairy cattle reproduction, reviewed the progression of timed-artificial insemination (A.I.) programs, discussed current recommendations and explained that timed-A.I.

Prosync labor rate