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The importance of heat detection

Rommel Ramos Published on 06 June 2011

It’s simple – accurate heat detection programs lead to higher pregnancy rates. Higher pregnancy rates result in more pregnant cows, fewer days open and more profitability for the dairy.

Having spent 11 years as the manager of a breeding team in Saudi Arabia and 14 years on different dairies (in Arizona and Oregon), I have seen firsthand the universality of good heat detection programs. Regardless of herd size, facility setup or climate, a successful reproductive program begins with knowledge and application of heat detection principles.



Profitability and heat detection

A good understanding of the heat cycle ensures accuracy in a heat detection program. On the flip side, failure to detect heat and errors in heat detection are the two primary causes of poor reproductive performance and low reproductive efficiency.

Inadequate heat detection affects profitability in a number of ways:

  1. 1. Undetected heats result in longer calving intervals, lower lifetime milk production and fewer calves.
  2. 2. Breeding cows unsuitable for insemination leads to lower conception rates and wasted semen and time (both are very costly).
  3. 3. Combinations of unrecognized estrus and low conception rates may lead to culling of normal cows.
  4. 4. Insemination of pregnant cows mistakenly identified in heat may cause abortion, especially if the breeder is inexperienced.

Detection of estrus is necessary for synchronization programs in dairy cows and is the key to successful use of artificial insemination (A.I.). While A.I. can provide exceptional genetic progress in a herd, it also places greater responsibility for heat detection on farm personnel.

Create a custom program

Developing a routine to observe heat and note the cow’s estrus activity helps A.I. occur in a timely fashion. In Saudi Arabia, we created a system that met the needs of the 5,000-cow operation. Because of the warm climate, A.I. was conducted at 4 a.m. and 6 p.m.

A trained breeder was also responsible for walking through all the breeding pens early in the morning, at noon and late in the afternoon to perform heat detection. Good communication between employees was crucial to maintain consistency between changing shifts.


Notes were shared regarding cows observed in standing heat and those in preheat. A weekly breeding summary was readily available on the breeder’s clipboard to double-check breeding data.

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To improve the success rate of heat detection, it is best for one person to be responsible for heat detection and adhere to a specific schedule. While heat detecting, keep in mind these important keys:

  • Early morning and early evening are the best times to observe cows in heat. Figure 1 shows the times of day cows are most likely to show signs of heat.
  • By making heat detection the first and last chore of the day, you can maximize the opportunity to observe late-evening and early-morning heats.
  • Involve all employees and communicate effectively. Cow pushers and feeders spend many hours of the day around cows. It is important to have a central location like a clipboard or whiteboard where these employees can record their observations.
  • To maximize conception rates, cows should be serviced within 24 hours of first observed standing heat. Keep this in mind when recording observations. If you are using technician service, also be aware of call-in times.

Signs of heat

No heat detection program can be a success without knowing what to look for. Observing and making note of secondary signs of heat will indicate which cows to watch for the primary sign of estrus – standing heat.

This period lasts an average of eight to 12 hours (but can be shorter in high-producing cows), during which time a cow will stand to be mounted. The preheat period can precede that for 10 to 20 hours. Many of the secondary signs shown below appear during preheat and are also present while the cow is in standing heat.

Secondary signs of heat:


  • Increasing amounts of clear mucus discharge from the vulva
  • Red, moist, slightly swollen vulva
  • Restless behavior: Bellowing, smelling other cows, butting with her head
  • Attempts to mount other cows, but will not stand to be mounted

The following herd behaviors are also important to note:

  • Grouping or congregating of cows. Studies have shown cows in heat or approaching heat tend to congregate, forming what is referred to as sexually active groups. These groups form during the preheat phase and disperse when the animals go out of heat. Keeping this in mind will help to identify not only the cows in heat, but those associated with them.
  • Cows show a preference for certain locations to exhibit estrus behavior. Knowing where these “hot spots” are can improve heat detection efficiency. Cows give preference to dry locations and soft footing, such as earthen floors or lots. Cows tend to avoid wet concrete and overly muddy areas.

Be cautious when heat detecting a group of animals being moved. Mounting activity may occur frequently in cattle being moved. In many of these situations, the animal being mounted has no route of escape and cannot be reliably identified as in standing heat.

Possess the proper tools

Equip heat detectors with the tools they need to succeed. Animals should be identified with clearly readable identification. An adequate supply of record-keeping materials should be available. Security lights or flashlights are necessary for nighttime observation, and a well-organized record-keeping system must be in place.

Be sure you have the necessary data by recording cow or heifer ID, time of observation and all signs of heat observed. Record all heat periods detected, even if the cow or heifer will not be bred on that heat. Together with breeding calendars or heat expectancy charts, this information can be used to help predict future heats.

Operating a successful heat detection program is not a small task. All individuals involved need to realize the importance of heat detection responsibilities. However, creating a successful heat detection program through thoughtful preparation, careful training and good communication is the foundation for a profitable reproductive program. PD

References omitted due to space but are available upon request to .

—Excerpts from Genex website: