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1108 PD: Sire conception rate (SCR) evaluation to improve A.I. programs

Bob Welper and Einko Topper Published on 24 July 2008

How much genetic improvement do you make in the absence of a pregnancy? None. How much milk will be created without a pregnancy? None. How much money will a dairy make without milk? None.

So, getting cows pregnant is obviously one of the most important functions on a dairy. Perhaps the most important one. A pregnancy is the source of a new lactation and a genetically superior heifer replacement. The management challenge, therefore, is how to maximize the number of pregnancies created on a weekly or monthly basis.



Progressive dairy producers will get a new tool to rise up to that challenge this summer, when the USDA releases a new evaluation called Sire Conception Rate (SCR) in August 2008. It promises to be a more accurate evaluation of male fertility, and it will provide valuable new information that you can use to improve the economic returns from your selection strategy.

The goal is pregnant cows

The breeding program on a forward-thinking dairy is first and foremost focused on creating pregnant cows. However, there are several factors that affect the likelihood of a cow becoming pregnant on your dairy.

Figure 1*illustrates that the chance of getting a cow pregnant is influenced by a range of factors. The most significant is management and environment. This relates to such things as cow comfort, nutrition, transition cow programs and people on the dairy. In comparison, genetics account for 4 percent of the variation in fertility. The fertility of the female accounts for 3 percent, while the service sire fertility is 1 percent.

Drilling down to the farm level on a large-herd shows a more detailed and wide range of performance on a sire by sire basis.


Sire fertility varies on the dairy

If you have ever generated a bredsum (DairyCOMP) by sire, you will have noticed that sire fertility can vary significantly. Figure 2* is from an actual dairy that shows an average conception rate of 35 percent. The range around that average is from 30 percent to 44 percent – or 14 percentage points!

It is important to note that this is data from a single dairy where the management and environment conditions are the same for all the breedings. So the influence is a constant, and relative differences are owing to sire fertility (and assuming the random breeding of cows with high versus low fertility themselves, which is not an unrealistic assumption).

Sire Conception Rate (SCR)

The USDA’s August release of Sire Conception Rate (SCR) is a researched effort to report the fertility performance on individual bulls marketed by A.I. companies. It will replace the Estimated Relative Conception Rate (ERCR) model for evaluation. Table 1* compares SCR and ERCR to show the main differences that matter to dairy producers.

With the SCR comes a more accurate approach to sire fertility evaluations – more than 20 percent more accurate than ERCR! Finally, the evaluation will be based on known pregnancy status. And the evaluation will use 100 percent of the data available and eligible, including data from cows undergoing multiple breedings.


In short, the A.I. industry is catching up to how progressive dairy producers actually determine sire fertility on their own farms – actual pregnancy exams.

How can SCR be used?

Like all sire proof information, SCR is another piece of information that can be taken into account when setting up your A.I. program. Clearly, you can make SCR part of your sire selection strategy.

If you have good management on the dairy, relatively high fertility sires can give your reproduction program an added boost that is simple to implement. To show how this works, let’s assume that the industry average SCR is 35 percent and that is the same average for your dairy.

Table 2* shows the predicted effect of using two different bulls, one with SCR +5.0 and SCR -5.0. The impact is 5 percent points higher pregnancy rate, when comparing high SCR vs. low SCR. This equates to six more pregnancies per 100 eligible cows for every 21-day cycle.

Show me the money!

Higher fertility has economic value. As we said earlier, a pregnancy is the source of both a fresh lactation of milk for harvesting and a heifer replacement. So it is not surprising that the economic value of a pregnancy is high. Reproductive specialists and dairy economists have combined to estimate the economic value of a new pregnancy.

Researchers have recently estimated the value of a pregnancy to range between $200 and $278 per cow. Applying these rates to the estimates of high versus low SCR sires in Table 2, the net result for six extra pregnancies will be between $1,200 and $1,668 in added value. The payback grows with every 21-day cycle, as more cows are getting pregnant faster.

The economic value of better fertility is tremendous and sometimes very simple to achieve. However, is it the only thing to focus on?

Pregnancies equal the power of genetics

While important, high fertility should not be the only selection criteria you use in your breeding program. Yet disregarding SCR will leave a huge economic return on the table and untouched. The fact is that genetics create the heifer replacements that you will milk in the future. So you should pay attention today to invest in the genetics that create the cows you want to milk in the future. Combining the production, health and type criteria important to you with higher fertility is a winning and profitable solution.

A big step forward

With SCR, the A.I. industry is paying attention to more accurate evaluations of sire fertility that will benefit producers. Just as we no longer have to look at conformation to guess whether daughters will last (see Productive Life), we can now measure the fertility of bulls directly by analyzing their actual fertility in the A.I. pens on well- managed dairies.

The takeaways:

  • The USDA will release the Sire Conception Rate evaluation in August 2008.
  • SCR is 20 percent more accurate than existing evaluation (ERCR) as it is based on known pregnancy status, all breedings, adjusts for inbreeding and includes an expanded service sire term that better accounts for stud-year differences.
  • SCR can be part of your sire selection strategy.
  • Sire fertility can deliver significant improvement in pregnancy rates and profitability.
  • Sire fertility and genetic merit should be combined in your A.I. program strategy. PD

Bob Welper and Einko Topper, Alta Genetics Director Production & Quality Control, for Progressive Dairyman

*Tables and figures omitted but are available upon request to