Timed AI Protocols: Double Ovsynch

By Andrew Sandeen

Timed artificial insemination (TAI) is a common reproductive management strategy used on U.S. dairy farms. It lessens the dependence on observation-based heat detection and provides a way to ensure that 100% of eligible cows are inseminated within a defined time window. A good TAI protocol can also help achieve excellent conception rates.

Ovsynch is a foundational TAI protocol that was developed in the mid-1990s (Pursley et al., 1995) and is widely used, though oftentimes with research-based additions to the protocol for the sake of improving cow pregnancy outcome. The core protocol is designed to synchronize ovulation of ovarian follicles, but it is more effective across a group of animals when combined with a good presynchronization protocol. Double Ovsynch, one such combined protocol, will be discussed in this article.

Double Ovsynch involves a series of treatments that are basically two Ovsynch protocols in careful succession. The entire Double Ovsynch protocol calls for two different types of hormone treatments over the span of about four weeks, with a total of at least seven times when the cow needs to be restrained for an injection or AI. One treatment that is administered several times is GnRH (designated as G in Figure 1), available with a variety of product names, including Cystorelin^Ò, Factrel^Ò, Fertagyl^Ò, and GONAbreed^Ò. The other injectable treatment is prostaglandin F_2α, (designated as PG), available under product names such as estroPLAN^Ò, Estrumate^Ò, Lutalyse^Ò, and Synchsure^Ò. Ideally, the final GnRH treatment (G4) should be administered about 56 hours after the second PG treatment (PG2) and be followed 16 hours later by AI, disregarding the presence or absence of observable estrus.

Figure 1. The Double Ovsynch protocol laid out in a weekly calendar format. The entire protocol can be shifted to any desired combination of treatment times, as long as the intervals between treatments remain the same: G1 – 7d – PG1 – 3d – G2 – 7d – G3 – 7d – PG2 – 56 hours – G4 – 16 hours – AI. The third PG is optional.

What Ovsynch1 Accomplishes

The first half of the Double Ovsynch protocol is intended to accomplish presynchronization, bringing the majority of cows into a similar stage of their estrous cycle with ideal conditions for the start of Ovsynch2. The aim is to increase the percentage of cows that are on days 5 to 8 of their estrous cycle with intermediate levels of progesterone in circulation and a healthy, dominant follicle that can potentially ovulate in response to G3. Catching most cows in this early stage of the cycle also decreases the risk of corpus luteum (CL) regression by natural means before the PG treatment of Ovsynch2, since it is best to maintain high progesterone concentration clear up to the time of PG treatment (Carvalho et al., 2018).

Inclusion of GnRH into a presynchronization strategy, as is done with Ovsynch1, increases conception rates by addressing the anovular condition that is present in many cows before initiation of the Ovsynch protocol (Fricke, 2018). In one research study, the use of Double Ovsynch reduced the percentage of animals with low progesterone concentrations at the start of Ovsynch2 (i.e., potentially anovular) from 25% down to just 5% and improved conception rates at the first postpartum service by 8 percentage points (Herlihy et al., 2012). In another study, Double Ovsynch increased the percentage of cows starting Ovsynch2 with a CL from 68% to 94% when compared to Presynch Ovsynch, clearly a reduction in the percentage of anovular cows (Ayres et al., 2013). These benefits are especially evident in first lactation cows (Souza et al., 2008).

An Improvement to Consider

Double Ovsynch is designed to synchronize ovulation precisely enough to allow for TAI and high conception rates. However, there is one challenge that has become a growing issue with high-producing dairy cows: a single PG treatment is sometimes inadequate for causing complete regression of a young CL induced by GnRH treatment (Carvalho et al., 2018), such as G3 of this protocol. Doubling up the final PG treatment by administering a second treatment 24 hours after the first treatment helps address the challenge, resulting in complete luteal regression nearly 100% of the time. Double PG treatment leads to an increase in conception rates by several percentage points (Borchardt et al., 2018), especially in older cows (Wiltbank et al., 2015). This extra PG treatment, as shown on Figure 1, is worth considering for improved TAI effectiveness.

Advantages and Disadvantages

In general, good presynchronization programs result in absolute conception rate improvements of 10 to 20 percent at first AI (Carvalho et al., 2018), and Double Ovsynch consistently ranks as one of the top protocols in terms of results.

Making the effort to administer a lengthy series of treatments with Double Ovsynch can pay off. Across several studies, the conception rate difference between Double Ovsynch and Presynch Ovsynch, another commonly used TAI protocol, significantly favored Double Ovsynch. Borchardt et al. (2017) found an approximately 4.5 percentage point advantage with Double Ovsynch, though most of the difference was amongst the primiparous cows. Success will vary from group to group, as was seen in one study where Double Ovsynch led to a significantly higher conception rate in primiparous cows (44%) than in multiparous cows (31%; Astiz et al., 2013).

Double Ovsynch also works well as a resynchronization protocol (Giordano et al., 2012), with higher conception rates as compared to regular Ovsynch (39% vs. 30%), as long as there is enough time to complete the entire protocol without sacrificing too many days open.

Conclusion

Double Ovsynch is an excellent, well-researched TAI protocol with proven success and significant advantages over most other protocols. It addresses some of the biggest challenges in reproductive management – heat detection, anovular cows, and conception rates – making it a potentially valuable option, but it does take commitment to the protocol and attentive management to make sure each treatment is administered to every cow at the correct time.

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