Select Sires - News BSE

Timed-A.I. Options: Another Tool from the Tool Box

by Dr. Ray Nebel, senior reproductive specialist

It is still possible to maintain good reproductive performance in dairy herds without synchronization and Timed A.I. (TAI), but it requires an effective systematic heat detection program that identifies approximately 70 percent of all possible heat periods. Unfortunately, maintaining such a heat detection program and quality heat detection personnel can be a never-ending challenge in today’s expanding herds. As the accuracy and efficiency of heat detection declines in many herds, the value of incorporating synchronization and TAI into the management program increases proportionately.

By grouping cows that calve within a one- or two-week window, cows can be precisely synchronized to allow for acceptable pregnancy rates and minimal labor inputs. It is easy to get confused by the variety of protocols available; however, this variety provides flexibility in developing a tailor-made program that works for you. I recommend you work with your veterinarian and Select Reproductive Solutions specialist to design a tailor-made program for your dairy.

Which protocol is best?
The good news is there are options if you are considering using TAI for first service. Larger herds (greater than 250 cows) usually start a new group of cows every week whereas smaller herds may start a new group every other week.

Three components of a total program consist of:

PreSynch – synchronization of cycles prior to TAI portion of the protocol
OvSynch – the protocol that allows for TAI
ReSynch – either at or prior to pregnancy determination for quick re-insemination

PreSynch: The objective is to have cows at a similar stage of the estrous cycle at initiation of the synchronization protocol prior to A.I.

Two injections of prostaglandin (PGF2α ) 14 days apart
Second PGF2α injection 14 days prior to OvSynch or CoSynch if desire is for injections to occur the same day of the week
Second PGF2α injection 11 or 12 days prior to OvSynch or CoSynch if objective is to maximize conception rates

OvSynch: Original “TAI” protocol eliminating heat detection

Timed A.I. should occur approximately eight to 18 hours after second GnRH injection
Interval between PGF2α and second GnRH is usually 48 hours, but 56 hour interval may provide higher conception rates

CoSynch: Similar to OvSynch but one less handling of cows

TAI at time of last injection of GnRH
One less handling of cows saves labor and may improve compliance
Heat detection and A.I. from PGF2α to GnRH will optimize success.

ReSynch: Cows to receive TAI following “open” diagnosis

Herds with excellent heat detection may choose to initiate ReSynch at pregnancy exams. (recommended for chalk/paint tail stripe herds)
Cows declared open are injected with GnRH and seven days later PGF2α, GnRH at 56 hours, and A.I. eight to 18 hours later
Option is to inject all cows seven days prior to pregnancy exam with GnRH
Cows declared open are injected with PGF2α , GnRH at 56 hours, and A.I. eight to 18 hours later
Pregnant cows should be confirmed approximately 30 days later

Times listed for TAI should be considered as the approximate average time of insemination. This should be based on the number of cows to inseminate, labor and facilities.

Compliance, as defined for a synchronization protocol, is the administration of hormone injections to the correct cows at the correct time intervals. The more complicated a protocol, the greater the chances are for procedural failure. Protocol compliance is critical for success. For example, the standard PreSynch + OvSynch protocol requires that each cow receives five hormone injections at appropriate days in milk and in the correct sequence. Failure to administer any one of these five hormones or administration in an incorrect sequence will result in a failure of the protocol to deliver an ovulated ova following insemination. If at each step a 95 percent compliance is achieved, the cumulative compliance becomes 77.4 percent which should not be acceptable. When selecting a synchronization protocol, two factors determine the success of any program – cycling cows in excellent body condition and compliance to the prescribed protocol.

GnRH - Cystorelin®, Factrel®, Fertagyl®, and OvaCyst®
PGF2α - estroPLAN™, Estrumate®, In-Synch®, Lutalyse®, and ProstaMate®

Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751