Heat Detection
What being on heat means.....
A Cow or heifer observed as being “on heat” is an animal that is showing the signs of being in estrus. Estrus, is the time in a cow’s reproductive cycle where she is sexually receptive. This period is just prior to when the cow ovulates. The cows estrous cycle can be between 17 and 24 days and is most commonly around 21 days.
During estrus which can last between 8 and 24 hours but most commonly around 18 hours, there is a rise in the hormone estrogen which is produced by the preovulatory follicle. There is also a rise in the luteinizing hormone which is produced by the pituitary gland. These hormone releases lead to ovulation which will occur around 30 hours after the start of estrus.
Esturs will not always be followed by ovulation and ovulation is not always accompanied by estrus. This is why a cow that is served by AI or a bull that may show all the signs of being on heat will not always be pregnant.
Signs of being on heat.....
The most obvious sign a cow is on heat is when she stands to be mounted by another animal in the heard, this can be a bull, another cow or young steers. This is why this part of the cycle is often called being “on standing heat”.
Other behaviours that may be observed before standing heat include: the animal attempting the mount other animals, vaginal mucus and a swollen vulva. Cows can also appear to be restless and bellow more frequently than usual.
It is possible for cows to have silent heats where they show no visible signs of estrus even though the normal follicular development and ovulation have occurred.
How to detect estrus....
Mount detectors are the most common visual aid for estrus detection. Adhesive patches are applied to the tailhead of the cow or heifer. After the animal has been mounted numerous times the patch will change colour as the top coating rubs off during the mounting.
Estrotect Breeding Indicators are a popular choice for this job. Patches that have less than 50% of the top coating removed are not considered activated – in the picture on the right these are the two patches on the left. The other three patches would indicate an animal has been on heat and should be inseminated.
If you do not have any breeding indicators tail paint can also be applied to the tailhead of the animal in the same place as the patch. If the paint is rubbed off by mounting action you know the animal has been in standing heat.
How to apply Estrotect Patches....
Estrotect heat patches are easy to apply and read – please watch this short video created by Estrotect to see how to correctly apply your patches.
This video was created by Estrotect – Enhance Genetics does not own the rights to the video.
When to use heat detection.....
If you are going to use Natural Heats to AI your cow or heifer heat detection is critical to success. You will need to observe “standing heat” and call your AI technician so they can come and inseminate approximately 12 to 18 hours (for coventional semen or 18 to 24 hours for sexed semen) after the onset of the standing heat.
If using FTAI heat detection is less of a necessity because we control when the hormones are administered we know when estrus should occur, however it is still good practice to monitor for signs of heat, as some breeds or particular cows can come on earlier or later than predicted and therefore timings can be changed.
