7-Day vs. 7n7 CIDR: What I Actually See in the Field

Both the 7-day CIDR and the 7n7 are solid sync protocols. I run both, and I do not have a default preference — the protocol gets matched to the producer's calendar and to what the group needs. What I want to share here is what I actually see in the chute, not a summary of the textbook.

The two protocols side by side

The 7-day CIDR protocol: CIDR insertion plus GnRH on Day 0, CIDR pull plus prostaglandin on Day 7, a second GnRH on Day 9, transfer on Day 17. Three producer-side events, 17 days start to transfer.

The 7n7: prostaglandin plus CIDR insertion on Day 0, GnRH on Day 7 with the CIDR still in, CIDR pull plus prostaglandin on Day 14, GnRH on Day 16, transfer on Day 24. Four producer events, 24 days.

What the 7n7 actually does for me on ET cows

On ET recipients, my conception rates on the two protocols are similar. I do not see a real difference per embryo transferred. What I do see is a slightly higher estrus rate on the 7n7, and that produces more usable recips on transfer day. Same conception, more cows I can put an embryo in. When the embryos are paid for either way, that matters.

Mechanism-wise: the 7n7 starts with prostaglandin and CIDR on Day 0. The prostaglandin kills any active CL the cow already has, regardless of where she is in her cycle, so I am not guessing about her status when I start. The GnRH on Day 7 then kicks off a fresh ovulation from a follicle that has been developing under the CIDR. By transfer on Day 24 the group is more tightly grouped on ovulation timing. Peer-reviewed work backs this up — Andersen and colleagues reported 40% ET pregnancy on 7n7 recipients vs 34% on 7-day CO-Synch + CIDR.¹ My field experience is closer to a wash on conception with a meaningful estrus-rate gap, but the direction is the same.

What I see on AI cows

On fixed-time AI, I see more cows in heat on the 7n7, and they come into heat in a tighter window than they do on the 7-day. That tightness is the practical advantage. When more cows are in heat at the same time, fixed-time insemination lines up better with actual ovulation across the group, and conception follows. Andersen's FTAI trial reported 86% estrus expression on the 7n7 versus 76% on the 7-day, with a corresponding pregnancy-rate edge.² The direction matches what I see at the chute.

On ET cows the 7n7 buys me more usable recips. On AI cows it buys me a tighter heat window. Neither effect is a 20-point swing in conception. Both are real and both show up consistently enough that I run the 7n7 whenever the calendar gives me the extra week.

When I run the 7-day instead

During the main breeding season, when programs are stacked and there is not time to add a week to every setup, the 7-day is the right call. Seventeen days from start to transfer is the difference between fitting a program into the calendar and not. A producer running multiple groups back to back does not have 24 days to give the protocol. The 7-day does its job and the operational tradeoff is worth it.

Running ET and AI groups on the same day

One thing I do regularly on operations that run both ET recipients and AI cows: run the 7-day protocol on the ET group while simultaneously running the 7n7 on the AI cows. Both protocols land on Day 17 — ET transfer and fixed-time AI happen on the same day. This is not a coincidence. The ET 7-day hits Day 17 for transfer; the AI 7n7 hits Day 17 for breeding. Start both on the same Day 0 and you have one breeding day instead of two.

One trip, one day in the chute, both programs handled together. Producers running mixed programs should know this option exists. It is one of the more practical scheduling tools available and it does not require any protocol modifications.

The thing that actually moves my conception numbers

More than the choice between these two protocols, what I see drive conception in recipients is whether the producer is feeding the group every day through the synch period and for at least 60 days after transfer. Cows on a steady or rising plane through that window establish and hold pregnancy at materially higher rates than cows on intermittent or declining feed. The published work on plane of nutrition and embryo survival lines up with this.³ ⁴ The protocol gets you to transfer day. Daily feed gets the pregnancy across the line.