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Timed Artificial Insemination

Timed AI protocols are based on the use of hormonal treatments that ensure tight synchrony of ovulation (tighter than what is achieved using estrous synchronization protocols). As a result, one can breed cows at a fixed time without the need for estrus detection and get good pregnancy rates.

The original timed AI procedure is called the OvSynch procedure. A typical OvSynch scheme is outlined below:

Original OvSynch protocol

Time	Treatment
Day 0, am	GnRH, 100 mg (2 ml)
Day 7, am	Prostaglandin 25 mg (5 ml)
Day 9, am	GnRH, 100 mg (2 ml)
Day 10, pm	Breed all cows (16 hours after GnRH)

The OvSynch program remains a good system for achieving timed AI. Nonetheless, since it was introduced, many other wrinkles have been introduced. For example, one can achieve higher pregnancy rates by either presynchronizing cows with two shots of prostaglandin 14 days apart before the start of the OvSynch program (Presynch-OvSynch). The idea here is to ensure that cows start the OvSynch protocol at the optimal time of the estrous cycle. In this system, the last injection of GnRH is delayed by 12 hours as compared to the OvSynch protocol.

A PreSynch-OvSynch protocol

Time	Treatment
Day 0, am	Prostaglandin 25 mg (5 ml)
Day 14, am	Prostaglandin 25 mg (5 ml)
Day 28, am	GnRH, 100 mg (2 ml)
Day 35, am	Prostaglandin 25 mg (5 ml)
Day 37, pm	GnRH, 100 mg (2 ml)
Day 38, am	Breed all cows

Also, an EAZI-BREED CIDR can be inserted at the same time as the OvSynch program is started. This program, called CIDR-Synch, helps trigger cows that are not cycling to start back up again and also keeps some cows from ovulating too soon.

Typical CIDR-Synch protocol

Time	Treatment
Day 0, am	GnRH, 100 mg (2 ml) Insert CIDR
Day 7, am	Prostaglandin 25 mg (5 ml) Remove CIDR
Day 9, am	GnRH, 100 mg (2 ml)
Day 10, pm	Breed all cows (16 hours after GnRH)

Many timed AI protocols fail on farms because the well-accepted protocols (the ones linked to on these pages) are not followed exactly, either because the dairy herd manager or veterinarian start tweaking the timing of the injections or because not every cow gets every shot on the day she needs it. One of the papers linked here describes the cumulative errors that result when only 90% of the cows receive each shot on the correct day.

Keep in mind that the timed AI protocols were developed and optimized in experiments using hundreds or thousands of cows. Don�t replace the protocols developed by the researchers who did these experiments with protocols designed by you based on personal experience or word-of-mouth. To get timed AI to work, you have to follow the protocols as they were designed.

Websites

Dairy herd synchronization programs � another overview of estrous synchronization and timed AI protocols from the University of Georgia

From the 100-day Contract � This Pfizer website provides a good overview of the original OvSynch protocol and actions to take after breeding

Ovsynch, Co-Synch, Presynch, and Kitchensynch: how did breeding cows get so complicated? - from Select Sires

Ovsynch, Pre-synch, the Kitchen-Synch: What�s up with synchronization protocols? � an excellent overview of the physiology, terminology, and effectiveness of the various approaches to timed AI. From the University of Wisconsin (disclaimer - there is no Kitchensynch, at least not yet)

Reducing the cost of OvSynch � a paper by Paul Fricke and others at the University of Wisconsin that describes how the costs of OvSynch can be reduced by costing the dose of GnRH