Veterinarian View | May/June 2022

Synchronization Tips for Spring

contributed article by Dr. Vince Collison, Collison Embryo | Collison Veterinary Services, Rockwell City, Iowa

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We’ve covered various synchronization programs in past articles. This is a summary of various points after several years of using these newer Synch programs and will touch on some of the latest things that are available.


Split Time AI

Split time AI will increase pregnancy rates. We’ve used this program on heifers for a couple of years and have seen very good results with it. We were using a seven-day CIDR (Control Internal Drug Release) program and gave Gonadotropin releasing hormone (GnRH) at the time of CIDR insertion. Seven days later we removed the CIDR and gave a prostaglandin injection and put an estrus alert on every heifer. In a window 64 to 68 hours later, we AI every heifer with a totally slicked off estrus alert.


At this point, we give every heifer a GnRH injection. Twenty-four hours later, we AI all the remaining heifers that did not have their estrus alerts slicked off the day before. Many of these will be slicked off at the time you AI on the second day. This has worked very well for us, and we have seen higher pregnancy rates than when we time AI all heifers simultaneously.


Extend Heat Detection

Extend heat detection out to 96 hours on programs where we heat detect and then time AI any remaining heifers at a set endpoint. We started doing this on heifers we would set up with a Melengestrol acetate (MGA) program and would have good results with it, so we have carried that out to programs where we set up heifers with a seven-day CIDR program.


Some producers like to AI off heat detection and then wrap up the group at a set endpoint. We’ve found that if you heat detect out to 96 hours there will be very few remaining heifers left to time breed at that point. Typically, on a group of 30 heifers, you may have as few as two head to time AI. So, if you see any heifers in heat at 96 hours, we will wait the 12 hours to AI those, but any that are not standing will get bred via AI at that time. We also give GnRH to the ones that are time bred at 96 hours. Of the ones we time breed we will typically see a 50 percent pregnancy rate and a higher rate overall for the group because we are performing AI based off standing heats.


The 7&7 Synch Program

The 7&7 Synch program has worked very well if you want to maximize the number of cows that display standing heat. Also, they will typically be synchronized very tightly. For recipient groups we normally give GnRH to cows that don’t show heats by 72 to 80 hours after pulling the CIDR. With this program there typically have been very few cows that don’t show heat by that point.


So, even though this program is an extra trip through the chute, there are so few that don’t show heat that it kind of offsets that. When we use a typical seven-day CIDR program, there can often be 20 percent of the cows not showing heat at the 72-to-80-hour mark. The other disadvantage of the 7&7 Synch is that it takes an extra week to set up and needs to be planned out earlier so the start date doesn’t get missed for a targeted AI date.


Timed AI Program

If you want the oldest and largest set of calves to market as commercial feeders, consider a timed AI program. This gives every cow an exposure to AI service on day one of the breeding season. Any returns to estrus will occur in 21 days when they are with the bull, so basically every cow gets two chances to get pregnant in the first 21 days. We have producers who collect their own bulls for this purpose. That way their semen cost is kept low, and the calf crop has uniform genetics.


Heat Watch System

When I first started the ET practice, we used a Heat Watch system. If a person really wants to get the highest number of cows pregnant, it was the way to go. It would log in the start time of the cow’s estrus, and we would time our AI off that. One thing that was very apparent with this system is that a lot of cows will start their estrus from 10:00 PM to 2:00 AM. Without this system, a lot of cows would probably be bred via AI too late because they wouldn’t be found in heat until 6:00 AM to 8:00 AM and then not bred until 5:00 PM that night. We would pull those cows in to AI earlier based off the time estrus started. Also, we would see cows that would only stand for four hours. We would still breed 12 hours from the start of standing heat with good results.


Also, a cow with a shorter standing estrus is likely to get missed if she would start cycling in the middle of the night. With a system like this, we didn’t have to synchronize cows as much and worked off natural heats. Or after logging heats for five days, we could go in and inject the remaining cows with prostaglandin and would see good response in those remaining cows. There are other similar systems being sold today.


Other advantages to these systems are there will be less need to use CIDRS which can offset the cost of these systems. There also will be labor freed up from heat detection. When done manually, heat detection typically starts to wane as the breeding season goes on.


learn more www.collisonembryo.com


Dr. Vince Collison is co-owner of Collison Embryo | Collison Veterinary Services PAC

in Rockwell City, Iowa.

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