Using 5-day Timed AI Protocols on Dairies

Penn State Extension

A 5-day protocol something to consider for your cows or heifers if a new TAI approach is needed.

There are four protocols for timed artificial insemination (TAI) of dairy cows recommended by the Dairy Cattle Reproduction Council (DCRC) on their 2018 reproductive management strategy sheet. One of the four options is a 5-day Cosynch protocol. The same protocol, adding use of a progesterone-releasing CIDR device, is offered as one of two good TAI options for dairy heifers. Five-day protocols are clearly worth considering for TAI in both groups.

Though there are several potential variations, here is what a 5-day protocol might look like:

What are the advantages of using a 5-day protocol?

  • If estrus detection is poor or inconsistent, then regular use of TAI can lead to more timely and effective inseminations.
  • For those who already rely on TAI for lactating cows but not heifers, it might be easy to expand use of the protocol.
  • The same protocol can be used for both virgin heifers and lactating cows. In general, heifers respond to TAI differently than lactating cows due to different circulating concentrations of reproductive hormones and patterns of follicular development. Some of the other TAI protocols commonly used for lactating cows are not as successful with heifers, but this one works well for both.
  • A 5-day protocol is shorter in duration than many of the alternatives.
  • All treatments can be performed at the same time of day. A common frustration with Ovsynch 56, one of the popular TAI alternatives for lactating cows, is having to administer the final GnRH treatment at a different time of day than the other treatments.
  • It may work well for herds performing pregnancy diagnosis on Wednesdays or Thursdays, allowing for immediate enrollment of nonpregnant cows in the protocol and reinsemination the following Thursday or Friday.

What are the drawbacks that might discourage use of a 5-day protocol?

  • There are a variety of treatments required, which involve costs and hassles.
  • Treatments occur on four different days of the week.

The other three TAI protocols on the DCRC sheet for lactating cows are all 7-day protocols. Through many research studies in recent years, the consensus is that 5-day protocols perform similarly to 7-day protocols (Fricke, 2018), and they can be paired with the same presynchronization options for improved results.

A few notes on research with 5-day protocols…

Across the scientific literature for TAI with heifers, 5-day Cosynch protocols typically result in the greatest fertility after TAI as compared to other protocols (Giordano and Masello, 2019). Importantly, Lima et al. (2013) demonstrated that including an initial GnRH treatment and second PGF treatment in a 5-day CIDR protocol are necessary for optimal fertility outcomes (Lima et al., 2013). This protocol is commonly called a 5-day CIDR-Synch.



In a recent heifer study, addition of a PGF treatment two days before initiation of a 5-day CIDR-Synch protocol resulted in greater conception rates when using conventional semen, but the advantage was lost when using sex-sorted semen (Karakaya-Bilen et al., 2019).

In lactating cows, a 5-day protocol may be especially useful for resynchronization. However, incorporation of the CIDR may only be necessary for a subset of open cows. Pulley and Stevenson (2015) showed that the most benefit from progesterone supplementation is for cows determined to have no corpus luteum (CL) and/or low progesterone. Progesterone supplementation improves dairy cow fertility within TAI programs, especially for cows without a CL (Bisinotto et al., 2015). Determination of CL status at pregnancy diagnosis may determine whether use of a CIDR will be advantageous.

Santos et al. (2010) found that use of the 5-day protocol without a CIDR outperformed a similar 7-day protocol (Cosynch 72) in terms of conception because of a reduced period of follicle dominance. They also confirmed that the second PGF treatment was necessary with the 5-day protocol to achieve more consistent luteolysis, which wasn’t used with the 7-day protocol. Similarly, Stevenson et al. (2018) found that, when using a 5-day TAI program, highest fertility was achieved when there was both an old and a new CL that were treated twice with PGF. There is some variability from study to study and farm to farm, but the protocol has been well-tested with competitive results.

There are plenty of options, but you might find a 5-day protocol something to consider for your cows or heifers if a new TAI approach is needed. Just remember that optimal results for first insemination of lactating cows occur when the TAI protocol is paired with a presynchronization strategy, as outlined on the DCRC protocol sheet.

The content of this article, including text, graphics, and images, is educational only and not intended to be a substitute for veterinary medical advice, diagnosis, or treatment. Always seek the advice of a licensed Doctor of Veterinary Medicine or other licensed or certified veterinary medical professional with any questions you may have regarding a veterinary medical condition or symptom.


Bisinotto, R.S., I.J. Lean, W.W. Thatcher, and J.E.P. Santos. 2015. Meta-analysis of progesterone supplementation during timed artificial insemination programs in dairy cows. J. Dairy Sci. 98:2472-2487.

Fricke, P.M. 2018. Evolution of timed AI protocols and overview of the 2018 DCRC Reproductive Management Strategies Protocol Sheet for dairy cows.

Giordano, J. and M. Masello. 2019. Heifer reproduction: Artificial insemination at estrus, timed AI, or both? 2019 Dairy Cattle Reproduction Council Conference Proceedings.

Karakaya-Bilen, E. E.S. Ribeiro, R.S. Bisinotto, A. Gümen, and J.E.P. Santos. 2019. Effect of presynchronization with prostaglandin F2α before the 5-d timed AI protocol on ovarian responses and pregnancy in dairy heifers. Theriogenology 132:138-143.

Lima, F.S., E.S. Ribeiro, R.S. Bisinotto, L.F. Greco, N. Martinez, M. Amstalden, W.W. Thatcher, and J.E.P. Santos. 2013. Hormonal manipulations in the 5-day timed artificial insemination protocol to optimize estrous cycle synchrony and fertility in dairy heifers. J. Dairy Sci. 96:7054-7065.

Pulley, S.L. and J.S. Stevenson. 2015. Five-day resynchronization programs in dairy cows including presynchronization and progesterone at two stages following artificial insemination. J. Dairy Sci. 98:6243-6255.

Santos, J.E.P., C.D. Narciso, F. Rivera, W.W. Thatcher, and R.C. Chebel. 2010. Effect of reducing the period of follicle dominance in a timed artificial insemination protocol on reproduction of dairy cows. J. Dairy Sci. 93:2976-2988.

Stevenson, J.S., J.A. Sauls, G.D. Mendonça, and B.E. Voelz. 2018. Dose frequency of prostaglandin F2α administration to dairy cows exposed to presynchronization and either 5- or 7-day Ovsynch program durations: Ovulatory and luteolytic risks. J. Dairy Sci. 101:9575-9590.

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