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Estrous Detection

Efficient and accurate estrus detection is the most important factor limiting reproduction in most dairy animals/herds. Efficiency defines the proportion of dairy animals seen in estrus of all animals eligible for showing estrus. Accuracy gives the percentages that were correctly identified as being in estrus. In a well-managed herd, the maximal estrus detection rate was found to be 60% of ovulations when dairy animals were observed two or three times daily. With continuous observations, the detection rate may increase to 95% in the second and later postpartum ovulations. Failure to observe animals in estrus delays first service, lengthens oestrus intervals, and is one of the primary factors lengthening projected average minimum calving to conception interval by increasing the number of days open. It contributes more to lengthy calving intervals than conception failure. In addition, inaccurate estrus detection lowers conception rate. Many animals are inseminated when not in estrus.  

Efficient reproductive management depends on the ability to detect estrus. There should be a systematic program for estrus detection. Criteria of such a program:

  • Frequency of observation (three times a day minimum)

  • Time allotted for observations (10 minutes per time for a herd of 50 animals)

  • Assignment of employees to estrus detection (no other duties at estrus detection times)

Employees should be trained in proper methods for estrus detection, semen handling and artificial insemination. If there is shortage of labour, investment in oestrus detection aids should be considered.

Estrus Detection Aids

These increase the efficiency of the estrus detection; although best method is visual examination but it is difficult in herd.

Marker Animals:
These are usually males that have been altered so that cannot mate but usually have sexual desire. These may be:

Teaser Animal:
These are surgically altered male, usually sterile. The most common method is vasectomy, removing the section of vas deferens. This prevents the sperm passage but still allowing the transmission of sexually transmitted diseases.

Gomer Animals:
There is surgically or non surgically alteration in direction of penis. When penis is erected, its direction is not straight. So when it mounts the cow, copulation does not occur. These bulls should not be large in size and weight.

Androgenized Cow or Heifer:
These cows are treated with male hormones.

Electronic Heat Detection Device:
They can measure the pressure applied to the female back, the activity level of female or the changes in hormone level.

Chin Ball Marker:
It is placed under the chin of the bull. It causes the paint to rub on the back of the cow on which it is mounted.

Ka Mar Heat Detector:
This device contains red dye and is glued on the tail. If the cow is mounted, the pressure on the device causes the dyes to mix, creating a visible colour change.

Electronic Pedometers:
These are motion sensors attached on the neck or fore leg. This sensor indicates the increased activity level associated with estrus by measuring the changes in amount of walking.

Blood or Milk Progesterone Kit:
It is used to measure the progesterone level. Normally it is less than 1 ng. During diestrus it is 8-11n g/ml.

Heat Expectancy Table or Record:
At the beginning of breeding season it can be used to generate a list of animals that should be cycle during a given time. Both primary and secondary signs should be recorded. It is also useful when animal will return to the next estrus specially in animal with silent heat.

Computerized Estrus Detection Aid:
Patches equipped with transmitters are glued to the tail head. When the mounting activity begins, the transmitter depresses and signals are sent to the receiver. Mounting data includes transmitter number, date, time and duration of mount. These are sent to the receiver and downloaded to computer.

We can also use dogs smelling or video camera.


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