Post-Breeding Strategies Part I
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Feb. 16, 2006
With Ray Nebel,
Senior Reproduction and Herd Management Specialist, Select Sires Inc.

Ray, this week we’re talking about post-breeding strategies to increase conception or decrease pregnancy lost.

That’s right, Bill. Recently, both in the popular press and in scientific journals, some data’s come to light that shows that there are some strategies that we can use, really GnRH, hCG, or CIDR’s, to decrease pregnancy loss or increase conception rates post-A.I.

So Ray, what’s the mechanism involved with this?

Bill, through research what we’ve seen is cows that don’t conceive, the progesterone level, it doesn’t get as high as cows that do conceive, and this occurs as early as six days after breeding.  So they’ve done a good bit of research where they’ve taken blood samples and looked at the progesterone levels and progesterone, of course, is a hormone that maintains pregnancy, so it makes a lot of sense. What we’re thinking is that a follicle that caused ovulation or where that egg came from is either not mature enough or large enough, so after ovulation it doesn’t get to mature size of the CL and doesn't produce enough progesterone so pregnancy's not maintained. 

So there are three different aspects to this? 

There are really three strategies on, how do we increase the progesterone post breeding? The first one would be GnRH injection or gonadotropin releasing hormone.  The gonadotropin releasing hormone goes back to the brain of the cow and causes her to release her own LH, which then works on that developing follicle, the next follicular wave soon after ovulation, and causes an accessory CL, or a second CL to ovulate causing a CL increased progesterone concentration.

The hCG, human chorionic gonadotropin, commercially sold under the name of Curion, That product works very similar except it works directly on the ovary.  It doesn’t go to the brain first.  It doesn’t go to the hypothalamus. It works directly on the ovary so that the developing follicle, for the next follicular wave if the injection’s given six, seven, eight days after A.I., causes it to turn over and turn into a CL so that we have two corpus lutea instead of just one, there we have higher progesterone.

A final application is the use of a CIDR.  The CIDR is a controlled internal releasing device, which contains progesterone--again this would be inserted day five, six, seven post-breeding. As soon as it’s inserted, almost immediately progesterone concentration goes up. However, it doesn’t really go up as high as the other two mechanisms. It goes up about 1.5 nano grams. To put this in perspective, that is about a third of what the CL normally produces. It can be left there for a week and removed. So all three strategies kind of give us the same outcome of increasing progesterone.