Select Sires

Top Dairy Records
for Reproductive Management
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired April 7, 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. There is a whole reproductive summary available with DHIA, Dairy Herd Improvement records. Many herds have their own milk-reporting equipment and they also report a lot of reproductive information. You are here to talk about a few points regarding that. We start with days open or calving interval.

Days open, or calving interval, is really kind of the bottom line number as far as evaluation of the reproductive program. Days open is the time that the cow is not pregnant, from the time she calves to the time she conceives. If we normally say we want a 13-month calving interval today, that would say that every 13 months we want that cow to have a calf. From the time she calves to the time she has her next calf would be the calving interval. Now, that relates to days open because days open would be that time period she is not pregnant. So we have a period that we call voluntary waiting period where we wait voluntarily not to breed her. This is because of the involution of the uterus, because of that 85- to 90-pound Holstein calf. The uterus has to come back down to normal size, she needs to get back her positive energy balance, and then we say we start breeding at 60 or 70 days-in-milk. So now, when we want to get her pregnant, we have roughly 60 days or three heat periods to get her pregnant. The days open are the management part of the calving interval.

Another one on the list is conception rate.

Conception rate, of course, is where we look at how many times we breed a cow and how many times it takes to actually get her pregnant. So, if we breed 100 cows and we get 100 pregnancies first time off, that is 100 percent conception, or one breeding per conception. However, in today’s high-producing dairies, the average conception rate is somewhere around 33 percent. So, for every three breedings, you get one pregnancy. The conception rate is something that we evaluate to say how well we are doing with the breeding part, as far as putting the semen in and producing pregnancies.

Another record is heat detection.

Before we can breed the cow, we have to be able to detect her in estrus. Now that man has gotten in between the natural bull-cow interaction, we have to detect when it is best the best time to put the semen into the female reproductive tract to produce that pregnancy. In today’s dairies we are usually catching a little bit less than half of the cows in heat. The national average would be somewhere around 40 percent. Only four out of ten heat periods are actually identified on today’s farms. A big part of that is that the farms have gotten larger, so there are more cows per person out there. And with the higher milk production, we have put some physiological constraints on the cow, such as that she doesn’t express estrus as well. And, the last factor would be our facilities. In a lot of cases today we are going for a maximum milk production, so we don’t want the cow away from her feed trough very often. There are usually free-stalls for her to lie down and rest, and close-by there is a feed bunk where she eats. So with eating, resting and milking there is not a lot of extra space for us to identify heat-detection. We put a lot of constraints on the modern dairy farm today as far as heat detection. That is why our percentages have dropped, I believe.

Ray Nebel, Extension Specialist and Professor of Reproductive Management at Virginia Tech.

Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751