Ovsynch Protocol (Part Two)
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Feb. 3, 2005
With Ray Nebel,
Extension Specialist and Professor of Reproductive Management,
Virginia Tech
This week’s Reproductive Moment is with Ray Nebel. Ray, we continue our discussion about Ovsynch protocol.
As I mentioned last week, Ovsynch was developed exactly ten years ago from research in Wisconsin. It entails three injections of hormones to synchronize ovulation. The first injection is GnRH, or Gonadotropin Releasing Hormone. Seven days after the Gonadotropin Releasing Hormone is administered, we give a prostaglandin, which causes a regression of the corpus luteum or "CL". And then, 48 hours or two days later, we give the last injection of GnRH, which initiates ovulation.
In the last three to four years, researchers have been trying to optimize this Ovsynch protocol, and what we will touch on is maybe three of the new variations of Ovsynch.
What are those?
The first one is called Presynch. As we stated before, Ovsynch is given at a random stage of estrus cycle. So, researchers have asked "Is there an optimum stage of the estrus cycle where we should start this procedure?" What they have found is that if we give two prostaglandin injections 14 days apart, and 12 to 14 days before we start Ovsynch, we can maximize our conception rate. With the first prostaglandin injection, cows that have a corpus luteum ("CL") are restarted into a new cycle. Cows that don’t have a CL have no reaction. So, 14 days later, the cows that were restarted two weeks earlier are started again, and hopefully the cows that did not have a CL now have their own natural CL. So, theoretically we should be pre-synchronizing 100 percent of the cows to be at mid-cycle, which has been termed to be the optimum time to start the Ovsynch program.
In the next step, after the Presynch trials -- and many people have accepted Presynch and have gone through Presynch protocols -- investigators have looked at timing of injections. The last GnRH injection, in initial research, was given so that no cow expressed estrus. We came in there without estrus expression, and put semen in cows that we did not see in estrus, which was hard for many people because for the last 50 years we recommended breeding cows based on signs of estrus. Now we are saying, you are not going to see them in estrus, but we still want you to put semen in them. It was very hard at first. When it was first designed we said we didn’t want to confuse producers, so we came in early and gave them Gonadotropin Releasing Hormone to start ovulation, but there were no signs of estrus. The tweaking of the program here is that delaying that last GnRH injection to 72 hours allows for that follicle to grow, and we get a more mature follicle, and again we see an increase in the conception rate.
The third improvement we’ve seen, or tweaked in the protocol, has actually been on the amount of hormone that we need to help in the economics of administration. We haven’t changed the prostaglandin. Prostaglandin has stayed at 25 milligrams or a 5-cc dose. However, the Gonadotropin Releasing Hormone was really developed for treatment of cystic cows. A cystic cow has a large follicle that has been persistent. Researchers then surmised that the follicle that we are trying to ovulate is a smaller follicle, and is more normal, so we wouldn’t need as much hormone. In fact, research has now shown that we can cut that dose almost in half, and save half the money on that injection. Where before it was recommended to use 2 cc’s or 100 micrograms, we could easily get away with 50 micrograms or a half dose, cutting the cost of the Gonadotropin in half.
Ray Nebel, Extension Specialist and Professor of Reproductive Management at Virginia Tech.
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