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Improving the Accuracy of Estrus Detection, One Cow at a Time

November 23rd, 2016

Improving the Accuracy of Estrus Detection, One Cow at a Time

Dairy producers are challenged to maximize pregnancy rates and keep cows calving at optimal intervals. One of the major hurdles is accurately detecting heats in cows. Several factors influence the accuracy of estrus detection in dairy cows, including the type of sensor used, the type of activity being monitored, how it is measured, the timeliness of alerts and the accuracy of the cow monitoring system used.

A number of sensors are available for heat detection in cows, but, in general, pedometers are among the most accurate. A study conducted by Roelofs (2005)1 showed that breeding 5 – 17 hours after an increase in walking activity results in high conception rates. The best outcomes typically occur between 11 and 16 hours after an increase in activity – a short window for insemination.

Neck-mounted sensors that record rumination and eating patterns are also highly accurate in detecting the onset of estrus. University studies have demonstrated the relationship between rumination and eating behavior (duration, intake, rate) and estrus in cows.2

While accurate estrus detection is the first step towards improving conception rates, producers must be alerted in a timely fashion to the onset of heat to take advantage of optimal breeding windows. Wireless systems that monitor and send producers alerts in real time will result in fewer missed opportunities. However, producers need to be cautious about breeding too early. One prominent research veterinarian found that new users of activity monitors often bred cows at the first signs of heat instead of towards the end, which can reduce conception rates.3

To determine the impact of better heat detection using a monitoring system, simply apply the following calculation:

Heat Detection Rate x Conception Rate = Pregnancy Rate

For example, with a typical Conception Risk of 33%, a difference of 9% in Heat Detection Rate between two systems provides a Pregnancy Rate difference of 3%, or an additional $40 per cow, per year, in income.

Even when cows are bred within the correct timeframe after heat begins, there are limitations to using conception rates to determine the accuracy of a monitoring system. Cows that conceive and lose the embryo before pregnancy checks can skew your data. According to Dr. Aurora Villarroel, a secondary metric – the proportion of insemination intervals longer than 25 days – is necessary to get a complete picture of reproduction in your operation. A large number of cows with lengthy insemination intervals in your herd can indicate problems with EED (early embryonic death), inaccurate heat detection or both.4 Talk with your veterinarian if you suspect problems with EED in your herd.

Accurate, timely detection of estrus cycles is an important part of maximizing the profitability of dairy operations. Knowing when to breed prevents missed opportunities and wasted resources. By incorporating automated estrus detection into dairy herd management, producers can act fast on reliable data with minimal false alerts and guesswork.

For more information about Afimilk cow monitoring systems, please visit, as well as Afimilk cow monitoring section.

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1 Roelofs J. When to inseminate the cow? Insemination, ovulation and fertilization in dairy cattle. PhD Thesis, Institute of Animal Sciences Wageningen (WIAS), The Netherlands, 2005.

2 Pahl, C. et. al. Feeding characteristics and rumination time of dairy cows around estrus. Journal of Dairy Science 98: 148-154. 2015.

3 Villarroel, Aurora. Don’t breed too early. Progressive Dairyman, pp. 65-66. April 19, 2016.

4 Villarroel, Aurora. How to Use Precision in Day-to-Day Management. 2016 Northeast Dairy Producers Conference. March 8, 2016. 

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