Post Breeding Strategies Part II
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Feb. 23, 2006
With Ray Nebel,
Senior Reproduction and Herd Management Specialist, Select Sires Inc.

Ray, this week we are talking about post breeding strategies to increase conception or decrease pregnancy loss.

There are really three strategies on how do we increase progesterone post-breeding. The first one would be GnRH injections, 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 to ovulation, and causes the follicle to ovulate causing the CL to increase progesterone concentrations. The hCG, human chorionic gonadotropin, commecially sold under the name of Curion, that product works very similar except that it works directly on the ovary; it doesn’t go to the brain first, it doesn’t go to the hyperthalamus. If the injection is given six, seven or eight days after A.I. it causes it to turn over and turn into CL so we have two corpus lutea instead of just one, there we have higher progesterone.

The final application is the use of a CIDR. The CIDR is a controlled internal releasing device that contains progesterone. Again, this would be inserted day five, six, or seven post-breeding and as soon as it is inserted, 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 nanograms. Now, to put this into perspective, that is about one third of what the CL normally produces. It is left in there for a week and removed, so all three of these strategies give us somewhat the same outcome of increased progesterone.

So, which strategy is best?

Well, there is one that I think is easy to rule out, it is the CIDR because you have two times you have to handle the cow; you have to put it in and you have to take it out. The other thing is it is more expensive. The CIDR devices are probably two to three times the price of either the GnRH or hCG. The data is still out on which one of the other two is really the best. Initial studies with GnRH were used for problem breeders, at the time of breeding and now looking at post-breeding or increased progesterone concentration. More recent research has focused on hCG because it works directly on the ovaries. Now hCG might be a little bit more expensive, but if it is more effective it might be a better strategy. I think we can rule out the CIDR, unless the farm is using CIDR’s for other things, cleans them up and uses them for this strategy. If that doesn’t occur, GnRH or hCG would be the best of the three strategies.

Looking at those two, would there be a reason not to go directly on the ovary?

It is a foreign protein. GnRH has only 10 amino acids in it, it is a natural compound, so it is not recognized by the animal as being foreign; hCG is human chorionic gonadotropin, so it is the hormone that comes from a human pregnancy. The human femals produces this compound; it is what most human pregnancy tests use to detect pregnancy in humans. It is a form of protein, even though it is small, it is foreign to the cow’s body and she will build up antibodies. The chance of anaphlactic reaction is very slim, but it is there, so that warning has to be taken.