Select Sires

SELECTIONS - Winter 2006
Evaluating Reproductive Performance

by Dr. Ray Nebel, senior reproduction and dairy herd management specialist

The ability to use records effectively is a cornerstone of reproductive management and is necessary to determine if adjustments need to be made in current management policies.

Complete herd records provide the tools necessary to define historic herd performance, assist in establishing goals, and allow monitoring to determine the impact of management changes.

The first step in record analysis is to identify the key components of reproductive performance that affect the desired outcome or goal. An example of important goals for the typical dairy are listed in Table 1.

Table 1 shows eight benchmarks of reproductive performance, each listed with intervention levels for monitoring the management policies of a dairy herd.

Table 1

First Service

The first step to a successful reproductive management program is to make sure animals promptly receive their first service shortly after the voluntary waiting period.

A scatter plot of days in milk at first breeding by calving date allows you to quickly visualize what is “really happening” on the dairy.

This graph will quickly reflect changes in management policy such as altered voluntary waiting period or implementation of a synchronization or timed A.I. protocol for first service.

Figure 1 represents a herd that breeds exclusively to detected estrus and would likely benefit from incorporation of Ovsynch or another timed A.I. program to reduce the number of cows not inseminated by 80 days in milk.

A.I. Submission Rate

More commonly known as heat detection rate, the A.I. submission rate is a barometer of how promptly a herd converts open cows into bred cows. The A.I. submission rate is generally accepted as a more appropriate term because Ovsynch is now being used quite extensively to present cows for breeding even though they were not detected in heat.

In many herds, cows are promptly inseminated for first service, but those that fail to conceive are not promptly diagnosed as open and (or) re-inseminated, resulting in lower than desired A.I. submission rates.

Conception Rate

Conception rate measures how well cows are conceiving after we present them for A.I. Conception rate combines the effects of cow fertility, semen quality, AI technique, heat detection accuracy, timing of insemination, as well as factors such as high environmental temperatures and cow comfort. The multitude of factors influencing conception rates makes diagnosing problems difficult and often frustrating.

Pregnancy Rate

Pregnancy rate is the reproductive performance benchmark that ties everything together and should be the cornerstone of any reproductive performance evaluation.

Pregnancy rate can be defined as the probability that an eligible, open cow will become pregnant within a 21-day period. Pregnancy rate is a product of the A.I. submission rate and the conception rate.

At the end of the day, pregnancy rate is really what is most important to dairy profitability.

Most herds would want to set a goal of at least 20 percent and as long as this goal is achieved, it makes little consequence in the bigger picture as to what the A.I. submission rate or conception rates were that got you there.

However, these variables will be important to consider when we look for opportunities to improve to the next level.

Percent Pregnant Analysis

Another question to ask is: “Are cows becoming pregnant when we want them to?” This can be addressed by graphing the rate that pregnancies are occurring as the lactation progresses, as shown in Figure 3.

Some herds may achieve acceptable “averages,” but do so by offsetting the cows that conceive too late with other cows that were bred and conceived too early. A good goal is 60 percent pregnant by 150 days in milk with no cow pregnant before the voluntary waiting period.

Hard Count of Pregnant Cows

From a timing aspect, another important question is how many pregnant cows must be generated weekly to maintain herd size and the desired calving interval. (See Figure 4.)

Without a constant flow of pregnancies into the herd, the milking string will be destined for a less than optimal head count at some point in the future.

Summary

Excellent reproductive performance is essential to the long-term success of a dairy operation. The ability to use records effectively is one of the cornerstones of reproductive management.

Each of the graphs in this article were produced by Select RePRO Analysis™, which was designed and developed to assist in the analysis and implementation of management decisions in Select Sires’ member herds. The program is in the final development stages and will soon be available in all member areas.

This program will be an important tool in Select Sires’ efforts to improve the profitability of our customers’ herds.

™Select RePRO Anaylsis is a trademark of Select Sires Inc.

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