Sync Protocols & Timing

The CIDR is a soft insert that releases progesterone into the cow during the sync window. The high progesterone level keeps her from coming into heat early and ovulating off-schedule. The GnRH injection at CIDR insertion either makes her ovulate right then or starts a fresh wave of follicles developing — what it does depends on where in her cycle she happens to be when you start.

When the CIDR comes out, the prostaglandin (PG) injection kills any CL the cow has at that point, which drops her progesterone fast. The second GnRH about 48 hours later then triggers a synchronized ovulation from the largest follicle that developed during the CIDR week. The whole goal is to get the group ovulating in a tight window, so the embryo age at transfer (for ET) or the AI timing (for AI) lines up with where the cows actually are in their cycle.

The 7n7 adds an extra seven days of CIDR exposure before the first GnRH. The cow is under progesterone the whole way in, so when you finally give the GnRH the follicle wave that responds is more uniform across the group. That is what tightens the ovulation window. Whether the extra 7 days and the extra farm visit are worth it depends on the program.

The 7-Day protocol is the shorter, simpler option. It works well across most programs. For producers running tight schedules, the shorter window (17 days for ET, 10 days for AI) reduces the time cattle are under active management.

The 7n7 adds seven days of progestin exposure before the first GnRH. The advantage shows up most clearly in herds where cycling status is less certain — cows that may be in anestrus, early post-partum cows that have not yet resumed cycling, or herds where the nutritional plane has been inconsistent. The extended CIDR window helps bring non-cycling cows into synchrony that the 7-Day would miss entirely.

For ET recipients specifically, conception rates on the two protocols are similar in my experience. What I see consistently is a slightly higher estrus rate on the 7n7 — which gives me more usable recips on transfer day. Same conception per transferred embryo, more transferable cows. That matters when the embryos are paid for either way.

For AI, I see more cows in heat on the 7n7, and they tend to come in heat in a tighter window than they do on the 7-Day. The published work on the 7&7 (Andersen and colleagues, Theriogenology 2020 and 2021) reports the same direction — they credit the extra CIDR week up front. My field results line up with theirs.

Protocol selection should be driven by the specific program, not a default preference. I do not run the same protocol on every client — body condition, cycling status, time of year, and program timeline all factor into the recommendation.

Sync protocols are precision tools for timing ovulation. They are not a substitute for nutrition. A thin cow on a flat or falling feed plane will sync on paper and fail on transfer day. A cow that is not cycling at all — open, post-calving, in deep anestrus — does not respond well to GnRH no matter which protocol you run. The protocol cannot manufacture a working reproductive tract from one that is not ready.

The single biggest factor I see between programs that hit and programs that miss is whether the producer is feeding the group every day through the synch period and for at least the first 60 days after transfer or AI. Cows on a steady or rising feed plane through that window hold pregnancy at materially higher rates than cows on intermittent or falling feed. This matches what the published work on plane of nutrition and embryo survival in beef cattle shows (Diskin and Kenny, Animal Science; UNL Beef extension).

The variables a protocol cannot fix: body condition direction, daily intake through synch and early pregnancy, and overall health of the cow. The most common reason for disappointing ET results is not the protocol — it is how the recipient group was managed going in and what they were fed coming out the other side.