Reproductive management is the profit engine of the dairy. A strong reproductive program delivers a steady pipeline of replacements, providing flexibility in herd management decisions. A subpar system is a profitability drag on the dairy, resulting in longer lactations, reduced milk production and the purchase of replacement heifers.

Lee john
U.S. Dairy Technical Services Veterinarian / Zoetis
Lee received his DVM from Oregon State University and is based in California.

So what is the secret to reproductive success? Really, it’s no secret at all. The key is getting more semen in more cows when they are most likely to become pregnant.

As the saying goes, “100 percent of the cows that aren’t inseminated will never become pregnant.” And the very best herds are able to get more semen in more cows than the average operation is able to do.

What drives pregnancy rate?
Pregnancy rate is the gold standard for reproductive measurement. It’s a figure that measures how many cows eligible to become pregnant during a 21-day cycle become pregnant.

The two drivers of pregnancy rate are heat detection risk (HR) and conception risk (CR). But which is the real driver for herds with excellent reproductive performance?


Excellent reproductive performance is most associated with reproductive management that results in excellent insemination management combined with average conception risk, according to research from the University of Pennsylvania.

In that study, published in the February 2013 Journal of Dairy Science, researchers looked at 16 high-performing herds. These herds were Dairy Cattle Reproductive Council award winners and ranged in size from 262 to 6,126 cows.

Pregnancy rates ranged from 26.5 percent to 39.4 percent. After comparing these herds with herds in the DHIA database, researchers found that the herds ranked in the 99th percentile for pregnancy rate, 99th percentile for insemination risk and around the 50th percentile for conception rate.

That means the very best herds rated the best in pregnancy rate and insemination risk (basically, the “risk” a cow would be inseminated) and were middle of the road for conception.

The researchers concluded that insemination management, resulting in a high insemination risk, drove reproductive success. In these high-performing herds, more than 75 percent of all cows are bred for the first time within 21 days of the end of their herd voluntary waiting period.

The insemination risk for repeat inseminations averaged 63.2 percent. Herd managers used a system that prepared cows for breeding and made sure semen was put in them as soon as possible and as often as possible.

How synchronization and activity monitors can help
Research into reproductive performance has focused on management technologies that help dairy producers inseminate open cows more often.

The introduction of synchronization programs ensured cows came into estrus and were inseminated in a window of time. Newer technologies such as automated heat detection share the same goal – identifying more cows ready for insemination.

As you evaluate the strengths and weaknesses of your own program, each technology raises questions. Is one better than the other? Can they work together?

To help provide some answers, researchers at the University of Guelph used three large Canadian herds to compare reproductive success using timed A.I. synchronization or automated heat detection. In total, they enrolled 1,429 cows on three dairies.

At the pen level, each dairy used one technology for six months and then switched to the other. They calculated results after one year.

Each herd used a different synchronization program and only one included a presynch. All herds practiced “cherry picking” and inseminated cows observed on visual estrus outside of timed A.I.

The researchers found little difference in each herd’s performance with a timed A.I. synchronization program and automated heat detection.

Between 19 percent and 32 percent of all inseminations were based on visually detected estrus, and herd performance improved by breeding cows in heat outside of the synchronization protocol.

The study showed slight improvement from the use of automated heat detection in the herds without a presynchronization program as part of their timed A.I.

However, this improvement was visible only when the “cherry picked” cows were removed from the data. These cows are likely the most fertile in the group, which reduced the success rate of the overall synchronization group.

What works best
Timed A.I. synchronization and automated heat detection through the use of activity monitors are two technologies that can help improve reproductive success. We believe most herds will likely benefit from a combination of synchronization with heat detection.

Using a synchronization program, including a presynch, can improve days to first service by ensuring all cows are inseminated soon after the voluntary waiting period.

Accurate heat detection following this first service will help identify open cows ready for re-insemination. Heat detection can be conducted in many ways, including activity monitors, tail chalk, mounted detectors and visual observation.

Before you change your protocols, review your breeding program with your veterinarian. No system is “one size fits all,” and your veterinarian has the best insight into your program and your needs.

In fact, as many as 25 percent of cows will not display estrus that automated heat detection can sense. It’s one of many reasons why a “one or the other” approach can be risky.

As you evaluate your program, identify strengths and weaknesses in your operation before you make a purchase. If you already have average or better heat detection rates, adding a technology such as automated heat detection may not deliver the gains you want.

Similarly, if you use a synchronization program that includes several GnRH injections, success from heat detection will be limited. GnRH is a hormone that reduces estrus expression. Herds with poor heat detection will likely capture greater gains from a technology investment.

The secret to reproductive success is not a secret. Most often, inseminating more cows improves the likelihood that more cows will become pregnant. PD

Lee received his DVM from Oregon State University and is employed by Zoetis as a dairy technical service veterinarian based in California.

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John Lee
Managing Veterinarian