Monitoring estrus intensity in cattle helps optimize reproduction

Estrus is a crucial indicator of whether a cow or heifer will successfully conceive. However, estrus cycles can vary significantly among individual females within a herd.

According to an October 2024 Bovine Veterinarian article, monitoring estrus intensity in cattle helps optimize reproduction and can be done efficiently with visual estrus detection aids.

University of British Columbia Animal Reproduction Professor Dr. Ronaldo Cerri is carrying out research to improve cattle fertility by identifying which cows and heifers are the best candidates to breed using tactics like artificial insemination (AI) and embryo transfer (ET), with estrus intensity as the deciding factor.

“Some cows will display estrus with less intensity for a shorter duration. They won’t walk around or be ridden as much,” says Cerri. “A cow in high estrus intensity typically has longer estrus and very intense physical activity which can be monitored.”

Cattle typically exhibit baseline activity when not in estrus, and when they start to enter estrus, their activity rises as the intensity of estrus increases. 

He notes being able to identify when estrus is about to peak is crucial for a successful pregnancy.

Breeding decisions

By analyzing extensive data from estrus detection sensors, Cerri and other researchers have identified patterns related to events occurring during estrus.

“The patterns are very consistent in many of the studies we do,” Cerri states. “Cows with lower estrus intensity always display less physical activity, but they also have lower pregnancy rates. On the flip side, cows with high estrus intensity display more activity and have higher pregnancy rates.”

Research conducted in the U.S., Canada, Brazil and Germany determined the same trend.

Cows with low estrus intensity often have lower progesterone levels during the growth of the ovulatory follicle, which increases their chances of failing to ovulate compared to those with high estrus intensity.

Understanding and managing a cow’s estrous cycle is crucial for successful cattle breeding, as it allows for precise timing of AI during the period when a cow is most fertile, leading to significantly higher pregnancy rates and improved reproductive efficiency.

Similarly, ET recipients exhibiting high estrus intensity have more consistent pregnancy results.

He adds, “Estrus intensity serves as a quality marker for a good cycle which leads to a better pregnancy via AI and ET.” 

Estrus intensity

Assessing the intensity of estrus using heat detection tools allows producers to identify the best candidates for breeding at any given time. 

Utilizing a mass breeding protocol, producers can also leverage estrus intensity to guide their selection of genetics.

“The more targeted a producer wants their breeding program to be, the more they can use estrus intensity information to make a breeding decision,” Cerri states. “Producers can identify high estrus intensity cows to receive sexed semen or ET because they are more likely to get pregnant and can use conventional semen for the low estrus intensity females.”

Cerri continues, “Producers can monitor estrus intensity by watching movement and mounting activity, but it really isn’t practical. This is why we need to utilize tools to helps us identify these events.”

There are various tools available for monitoring estrus, including activity monitors, tail paint or chalk and breeding indicator patches. However, some tools provide more information than others and come with certain trade-offs.

“Activity monitors are quite effective at measuring estrus intensity, but not everyone can utilize them,” Cerri states. “Breeding indicator patches are another option that can give producers a subjective measure and score estrus intensity, which is probably better than other inexpensive options like tail chalk.”

According to research, by using breeding indicator patches, producers can monitor estrus by checking for patches with 50 percent or more of the surface ink rubbed off. 

This indicates the female is in high estrus intensity and ready to breed. Conversely, if less than 50 percent of the ink is rubbed off, the female is at low estrus intensity. 

In this case, a producer might consider breeding her with lower-cost genetics or waiting to breed until she has reached high estrus intensity.

“Estrus and the intensity of estrus within cows are important pieces of information to add to a reproduction program,” Cerri concludes. “Once a producer has this information, they’ll have better predictions of what their cows will do, making them more efficient and profitable.”

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.