Pregnancy Rates (Part Three)
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Feb. 24, 2005
With Ray Nebel,
Extension Specialist and Professor of Reproductive Management,
Virginia Tech
This week’s Reproductive Moment is with Ray Nebel. Ray, the last couple of weeks you have been talking about pregnancy rate, how its value is becoming more and more important because it tells you what is currently going on in the herd, as far as getting cows pregnant. You mentioned two big areas with pregnancy rates. There is first service pregnancy rate and the other is repeat service with resynchronization. Let’s start by reviewing what you said about first service.
Roughly ten years ago was when the data first came out on ovulation synchronization, commonly known as Ovsynch. This kind of revolutionized the way we breed cows, as least in the dairy situation, in that we now can set up cows so that first service can occur when we want it to. We are not depending on the cow to tell us when she wants to get bred. Most people would look at an interval between 60 and 75 days as when they would program for service. The pregnancy rate we would expect on first service is usually higher than the pregnancy rate on following services, the reason being that, with these cows, we have the whole population and there is a higher percentage of normal cows. In every herd there is a percentage of cows that are going to be harder to breed, or "hard breeders". If we take a herd of 200 cows, then it might only be 10 percent, or 20 cows. So, in first service we have 180 cows that are pretty much normal, and we have 20 problem cows. But, in second service, after we’ve gotten say 35 percent of them bred, and the pregnant cows are removed from the breeding population, those 20 cows then become a higher percent of the number of cows eligible to be bred (non-pregnant cows). We expect second and third service to be slightly lower because of this effect.[*] So, with first service pregnancy rate, the goal is to be somewhere between the mid 20’s to 30’s, while with overall pregnancy rate we are shooting for 20 percent. If we achieve that, then we are doing pretty well.
Is there a way to increase those rates on second and third service?
We are just now doing research on resynchronization. We don’t know what cows got pregnant on first service, but what we can do is a week-before pregnancy check. When we know the veterinarian is coming for a pregnancy exam next week (in seven days), those cows that were serviced on first service we give an injection of Gonadotropin Releasing Hormone (GnRH). This is the first injection of the Ovsynch program, and really saves us a week in the synchronization program. So, if a cow is diagnosed open when we start, the next step would be prostaglandin. That cow is bred two to three days after she is diagnosed open by the veterinarian. This saves a whole week in the program. A week might not sound like much, but as we go on, that week’s numbers would save something like $21 to $25 per cow.
Good for the pocketbook.
Oh yes, really! As the herd gets larger, that value really can amount to a significant savings.
Are you finding that the dairy producers are catching on to this?
As I said, it started ten years ago, and for a procedure that is as young as this one is, it is starting to catch on. It is catching on in larger herds and more progressive herds where the breeders are wanting to take control of the reproductive program.
The more you talk about it, the more it might catch on.
I hope so.
Ray Nebel, Extension Specialist and Professor of Reproductive Management at Virginia Tech.
(*) See an example of why this is true.
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