Conception Rate Versus Pregnancy Rate
(Part Two)
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired April 21, 2005
With Ray Nebel,
Extension Specialist and Professor of Reproductive Management,
Virginia Tech
This week’s Reproductive Moment is with Ray Nebel, Extension Specialist and Professor of Reproductive management at Virginia Tech. We continue where we left off last week, Ray. We are talking about Conception Rates versus Pregnancy Rates and how looking at service numbers gives us a target on where to start. Let’s talk about the role of the technician.
Usually on today’s farms there is more than one person breeding cows because of the time off, and often the size of the herd. So it is very good when a cow is bred with a recommended procedure, in that we write down who does the breeding, so that we can come back and ask, "On this group of cows, with technician one, technician two and technician three, what kind of conception rates does each one of them have?" Some people might do better breeding heifers, versus cows. Some people might do better breeding on a weekend versus during the week because of time constraints. But, if we need to retrain an individual, if we have one person that is 10 to 15 percent lower than the other individuals on the farm, it doesn’t say that there is a cow problem, it says that one of the technicians probably needs to go back to a refresher course and bone up on all the little parts that it takes to get cows pregnant.
What is a breeding trigger?
The breeding trigger is, "Why do we want to breed that cow?" Is it a standing heat, was it a KAMAR®, was it unusual activity, was it a pedometer, was it induced heat from an Ovsynch or Pre-synch program or one of the hormone programs? What is recommended with the breeding trigger is, again, to find out, when we breed that cow, who bred her, which technicians, and why did we breed her. Was she in standing heat? Was she on an Ovsynch program? Was it a triggered KAMAR? And again, we can go back and say that when we breed cows in KAMARs we expect on this farm we are going to get about a 20 to 30 percent drop in conception. Now, the recommendation might be that we quit breeding those cows and try to bone up and do a better job in visual heat-detection.
What about the monthly conception rate report?
It is important because throughout the country the seasons really have an effect, and environmental temperature has an effect on our conception rate. If it is too big of a factor it might say that we need to adjust or change our facilities, especially in the southwest, in the south and some out in the west. In the summertime, the summer heat and humidity can really lower conception rates, even drop them in half or lower. Now, if we see a drastic reduction, more than half, it says that the facilities probably need some heat abatement: some sprinklers, some fans. So we can kind of give you a clue whether we need to make some modifications in our facilities to give us more cow comfort to help with conception. In the wintertime we might have heifers out on pasture with very little shelter. In a very harsh winter environment we are going to see lower conception rates. Again, that should trigger the building of a shelter or a barn to bring those heifers in, which would help us with some conception rates.
With the monthly conception rate report, what we really can tell is whether the facilities are really keeping up to par, as far as cow comfort, to allow us to have optimum conception.
Again, how do they differ from the pregnancy reports?
The pregnancy rate report would say that every 21 days we would get a report of how many cows get pregnant. Now, we can get a pregnancy report by lactation number, or we can get it by days-in-milk. If we start out every 21 day period, how many cows get pregnant? Of the total number eligible to become pregnant, how many do we catch in heat? And how many actually become pregnant? In fact, pregnancy rate should be the most-used figure, as far as evaluating the reproduction, because it changes every 21 days. Heat-detection conception rate and days open are rolling averages so there are 12 months worth of data there. It doesn’t change very quickly when you do a management change, but conception rate doesn’t have a time element. It is just how many times we bred a cow, and how many times we got a pregnancy. Where, pregnancy rate actually brings in the time element as how many cows were eligible in this 21 days, and how many did we get pregnant. It brings the time element into the picture.
That is Ray Nebel, Extension Specialist and Professor of Reproductive Management at Virginia Tech.
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