Timed AI Protocols: Presynch Ovsynch
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 foundational TAI protocol called Ovsynch was developed in the mid-1990s (Pursley et al., 1995) and is widely used, though oftentimes with research-based modifications to improve cow response. The core protocol is designed to synchronize ovulation of ovarian follicles. Though Ovsynch is a useful reproductive management tool, not all cows respond similarly when it is started at a random stage of their estrous cycle. When Ovsynch is combined with a good presynchronization protocol, follicular responses are better coordinated, and the resulting fertility rates are improved. Presynch Ovsynch is one such combined protocol, which will be discussed in this article.Â
The entire Presynch Ovsynch protocol requires two different types of hormone treatments over the span of about five weeks, with a total of at least six times when an individual cow needs to be restrained for an injection or artificial insemination (AI). One treatment administered twice is gonadotrophin-releasing hormone (GnRH; designated as G1 and G2 in Figure 1), available with a variety of product names, including Cystorelin®, Factrel®, Fertagyl®, and GONAbreed®. The other injectable treatment is prostaglandin F2α, (designated as PG), available under product names such as estroPLAN®, Estrumate®, Lutalyse®, and Synchsure®. Ideally, G2 should be administered about 56 hours after the third PG treatment (PG3) and be followed 16 hours later by AI, disregarding the presence or absence of estrous activity.
What Presynchronization Accomplishes
Presynchronization, the first portion of the protocol that precedes the Ovsynch portion, is achieved with PG treatments in the weeks leading up to the initiation of Ovsynch. Presynchronization treatments help bring the majority of cows into a similar stage of their estrous cycle to better manage the conditions at G1 for an optimal starting point.
The general objective of presynchronization is to increase the percentage of cows that are on days 5 to 8 of their estrous cycle, with intermediate levels of progesterone in the circulation and a healthy, dominant follicle that can ovulate in response to G1 administration. Catching most cows in this early stage of the cycle also decreases the risk of CL regression by natural means before the PG treatment towards the end of Ovsynch. Success rates are highest when circulating progesterone remains high clear up until the time of PG treatment (Carvalho et al., 2018).
Timing of Presynch
When two PG treatments are used for presynchronization, it is most common to have a two-week interval between the first and second treatments. The interval between the second treatment and G1 of Ovsynch is more variable. Usually, the selected interval is somewhere between 10 and 14 days, as noted on Figure 1.
Though a 14-day interval between PG2 and G1 is sometimes a convenient option, if the Presynch Ovsynch protocol is being used for 100% of first service inseminations, a shorter interval (i.e., 10 to 12 days) is recommended because of better conception rates (Fricke, 2018). Galvão et al. (2007) found that shortening the interval from 14 to 11 days was effective in increasing the ovulatory response to G1, with most cows set up to be between day 5 and 8 of the estrous cycle at G1. Conception rates were higher with the shorter interval. However, it is not advisable to make the interval shorter than 10 days (Colazo et al., 2013).
An Improvement to Consider
A single PG treatment is sometimes inadequate for causing complete regression of a young CL induced by G1 (Carvalho et al., 2018). Doubling up the final PG treatment by administering a second treatment 24 hours after the first treatment helps accomplish 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 treatment, as shown in Figure 1, is worth considering for improved TAI effectiveness.
Advantages and Disadvantages
In general, good presynchronization programs have resulted in conception rate improvements of 10 to 20% at first AI (Carvalho et al., 2018). Though Presynch Ovsynch isn't the top protocol in terms of results, it has some management advantages (e.g., number of treatments and "cherry picking") and has clearly been shown to improve conception rates when compared to Ovsynch by itself (Moreira et al., 2001).
One reason Presynch Ovsynch is a popular option, besides the simplicity of it, is that it allows for "cherry picking." If cows are eligible for breeding after one or more of the presynchronizing PG treatments, they can be inseminated before completion of the entire TAI protocol. One word of caution, however, is that this practice may result in lower conception rates than could be achieved if all cows went through full Presynch Ovsynch TAI protocol (Gumen et al., 2012). Advantage – cows inseminated sooner with fewer injections. Disadvantage – lower conception rates than are possible with other options.
Across several studies, the conception rate difference between Presynch Ovsynch and Double Ovsynch, another commonly used TAI protocol, significantly favors Double Ovsynch. Borchardt et al. (2017) found an advantage of approximately 4.5 percentage points using Double Ovsynch, though most of the difference was amongst the primiparous cows.
The biggest disadvantage with Presynch Ovsynch is that it does not help induce ovulation in anovular cows, which are a common and significant issue across the dairy industry. Double Ovsynch, by comparison, was shown in one study to reduce the percentage of animals with low progesterone concentrations at G1 of Ovsynch (i.e., potentially anovular) from 25% down to just 5% and improve conception rates at the first postpartum service by 8 percentage points (Herlihy et al., 2012). Again, the difference is especially evident in first lactation cows (Souza et al., 2008).
Conclusion
Presynch Ovsynch is a good, well-researched TAI protocol with proven success and significant advantages over Ovsynch alone. It is a convenient protocol relative to some of the other high fertility options, but it won’t achieve maximum conception rates. Determine which factors (e.g., early insemination, maximum conception rates) are most important to decide if cherry picking is a worthwhile strategy and aim for an interval around 11 days between PG2 and G1, if possible.
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References
Borchardt, S., Haimerl, P., Pohl, A., & Heuwieser, W. (2017). Evaluation of prostaglandin F2α versus prostaglandin F2α plus gonadotropin-releasing hormone as Presynch methods preceding an Ovsynch in lactating dairy cows: A meta-analysis. Journal of Dairy Science, 100, 4065–4077. doi:10.3168/jds.2016-11956
Borchardt, S., Pohl, A., Carvalho, P. D., Fricke, P. M., & Heuwieser, W. (2018). Short communication: Effect of adding a second prostaglandin F2α injection during the Ovsynch protocol on luteal regression and fertility in lactating dairy cows: A meta-analysis. Journal of Dairy Science, 101, 8566–8571. doi:10.3168/jds.2017-14191
Carvalho, P. D., Santos, V. G., Giordano, J. O., Wiltbank, M. C., & Fricke, P. M. (2018). Development of fertility programs to achieve high 21-day pregnancy rates in high-producing dairy cows. Theriogenology, 114, 165-172.
Colazo, M. G., Ponce-Barajas, P., & Ambrose, D. J. (2013). Pregnancy per artificial insemination in lactating dairy cows subjected to 2 different intervals from presynchronization to initiation of Ovsynch protocol. Journal of Dairy Science, 96, 7640–7648. doi:10.3168/jds.2013-6750Â
Fricke, P. M. (2018). Evolution of timed AI protocols and overview of the 2018 DCRC Reproductive Management Strategies protocol sheet for dairy cows.
Galvão, K. N., Sá Filho, M. F., & Santos, J. E. P. (2007). Reducing the interval from presynchronization to initiation of timed artificial insemination improves fertility in dairy cows. Journal of Dairy Science, 90, 4212–4218. doi:10.3168/jds.2007-0182
Gumen, A., Keskin, A., Yilmazbas-Mecitoglu, G., Karakaya, E., Alkan, A., Okut, H., & Wiltbank, M. C. (2012). Effect of presynchronization strategy before Ovsynch on fertility at first service in lactating dairy cows. Theriogenology, 78, 1830–1838.
Herlihy, M. M., Giordano, J. O., Souza, A. H., Ayres, H., Ferreira, R. M., Keskin, A., Nascimento, A. B., Guenther, J. N., Gaska, J. M., Kacuba, S. J., Crowe, M. A., Butler, S. T., & Wiltbank, M. C. (2012). Presynchronization with Double-Ovsynch improves fertility at first postpartum artificial insemination in lactating dairy cows. Journal of Dairy Science, 95, 7003–7014. doi:10.3168/jds.2011-5260
Moreira, F., Orlandi, C., Risco, C. A., Mattos, R., Lopes, F., & Thatcher, W. W. (2001). Effects of presynchronization and bovine somatotropin on pregnancy rates to a timed artificial insemination protocol in lactating dairy cows. Journal of Dairy Science, 84, 1646–1659.
Pursley, J. R., Mee, M. O., & Wiltbank, M. C. (1995). Synchronization of ovulation in dairy cows using PGF2α and GnRH. Theriogenology, 44, 915-923.
Souza, A. H., Ayres, H., Ferreira, R. M., & Wiltbank, M. C. (2008). A new presynchronization system (Double-Ovsynch) increases fertility at first postpartum timed AI in lactating dairy cows. Theriogenology, 70, 208–215.
Wiltbank, M. C., Baez, G. M., Cochrane, F., Barletta, R. V., Trayford, C. R., & Joseph, R. T. (2015). Effect of a second treatment with prostaglandin F2α during the Ovsynch protocol on luteolysis and pregnancy in dairy cows. Journal of Dairy Science, 98, 8644–8654. doi:10.3168/jds.2015-9353
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