The Importance of Good Heat Detection

Most dairy cattle now become pregnant through the means of artificial insemination (AI). Therefore, it is important to understand how to perform accurate heat detection on your farm to enable higher conception rates for the herd. A good conception rate leads to achieving improved calving intervals (aiming for 365days) which, in turn, leads to improved cow productivity and herd profitability.  

A cow’s reproductive cycle lasts approximately 21 days; however, this varies between cows and can be expected to run anywhere between 18 and 24 days. Oestrous behaviour (or a heat) occurs approximately 24hrs before ovulation. When ovulation occurs, an egg is released and there is a chance of pregnancy if semen is present. Ideally, cows should be AI’ed 8hrs after the first signs of showing heat. This leads to the semen being present in the reproductive tract at the time in which the egg is released. Hence, AI’ing should be performed using the “AM-PM” rule – a cow first showing heat in the morning, should be AI’d that afternoon and vice-versa.

There are 2 main errors identified on farm when it comes to heat detection:

  1. Missing cows on heat; and
  2. Misidentifying cows as on heat when they are not

The most reliable behaviour a cow will show on heat is standing to be mounted by other cows and the presence of a mucus/slime “bulling string”. However, various factors mean this is not always seen. Due to the high productivity of the modern dairy cow and the layout of most cubicle housing; dairy cows can have what is called “silent” heats in which heat behaviour is minimal and hard to detect. A heat should last approx. 12 hrs; however, it has become more common for them to last as little as 8hrs. In addition, studies have shown that most heats occur between 8pm and 8am. This means, detection protocols must be robust to detect as many cows that are on heat as possible.

Many farms now employ outside agencies to perform heat detection and AI services. This has proved to be very successful due to time and staff pressures on many farms. If this is not an option for your farm, some options which can help improve heat detection on farm are below:

  1. Regular checks by staff during the herds “rest” times
    • The cows should be observed quietly and from a distance 3 times per day – e.g. 2hrs after each milking and in the mid-afternoon.
    • Clear identification is important to prevent misidentification.
  2. Tail paint/chalk
    • This is cheap and easy to apply but requires staff that are skilled in identifying rub marks which indicate heat.
    • Paint should be reapplied at least weekly.
  3. Heat mount detectors
    • These are cheap and easy to apply but care should be taken in case the detector has been rubbed due to a knock rather than mounting.
  4. Teaser bulls
    • A teaser bull is a very accurate way to detect heats in the herd. However, the safety of having a bull in the herd and costs must be considered before investing in this form of detection.
  5. Milk progesterone testing
    • A low progesterone indicates oestrous/heat, and it is very accurate.
    • Costs must be considered as ultimately multiple tests per cow may be required. Staff also must be trained in reading the test strips.
  6. Activity monitors
    • New technology has brought numerous monitors to the market which are very accurate and can give you real-time information on heat behaviour of cows in your herd, straight to your phone.
    • These systems to require considerable investment and training of staff is required to understand all the data that they present.

In summary, whichever tools you use to detect heat; it is important to get it right. By implementing effective heat detection strategies, this can improve conception, make the breeding programme more efficient, help maintain herd productivity and ultimately enhance farm profitability.

Fane Valley Stores supply various heat detection aids to help make heat detection easier on farm.