However, one big obstacle many farmers face is when their cow, apparently, just doesn’t go into heat.

Does that mean they are infertile? Not necessarily.

Your cattle may just have a silent heat.

What is a silent heat?

A suboestrus or silent heat in cattle, is defined as the lack of behavioural oestrus symptoms, although the genital organs undergo normal cyclical changes. The incidence of silent heat varies from 10% to 40% between different herds.

A cow with a silent heat doesn’t display any of the obvious signs, such as licking or sniffing other cows, mounting, standing to be mounted, or acting nervous and excitable.

However, she can still become pregnant and the bull will know about it, even if they’re vasectomised. But you won’t.

This is why these vasectomised (or teaser) cows are used for heat detection. They are the same as a stock bull essentially, but because the tubes that deliver semen have been cut, they can’t inseminate a cow.

If you get the procedure done, don’t let the bull in with the cows for a month because his sperm could still be viable.

A chin ball can be fitted to a teaser for adding paint to the cow as she is mounted. This device requires a lot of maintenance, as you have to top up the paint every 15 to 20 mounts.

Additionally, it can only tell you so much, unless you go back and check how progress is going regularly and take lots of notes.

Moocall HEAT

The Moocall HEAT collar is Moocall’s heat detection system whose unique design uses the bull’s natural ability to your advantage.

It comes in two parts:

  • A collar (for the bull).
  • Moocall RFID tags, one for each cow you’re breeding.

    • The system can tell you which cow is in heat, when the bull detected it and how strong it is.

    It doesn’t need to be monitored or adjusted and sends the information straight to your phone, which means you don’t have to spend hours every day checking for signs of heat.

    Consider it like a chin ball for the modern farmer – with a miniscule margin of error.

    How silent heat in cattle happens

    Silent heats occur when not enough progesterone is being produced. Progesterone acts along with oestrogen to manifest itself in visual signs of heat in a cow or heifer.

    In heifers, the oestrus associated with first ovulation is usually silent because not enough progesterone is being produced yet.

    However, during second ovulation, progesterone from regressing corpus luteum act synergistically with estrogen to produce oestrus symptoms.

    Causes of silent heat

    Heat stress

    Environmental temperatures of over 32 degrees can lead to silent heats in cattle. This is more prominent in cattle with more black markings, as they absorb more of the sun’s rays.

    Heat stress reduces the duration and intensity of oestrus, which in turn leads to lower mounting activity. Implementing Moocall HEAT catches your silent heats, so it is like a silver bullet to a lot of these problems.

    Iodine

    If iodine is limiting (it is generally quite deficient in New Zealand), it can also reduce the behavioural response of a cow in oestrus.

    Other stress

    Any type of stress can be a cause of silent heats. Some farmers have even claimed that their cows are more prone to silent heats during wet weather.

    Predisposition

    Every cow is put together a little differently and some are more wont to silent heats than others. One tell-tale symptom of this in a cow that doesn’t show any other signs of heat is mucous coming from her vulva every ~21 days. This typically signals that heat is over.

    If you know what to look out for, you can run a bull with her. However, this requires a lot of surveillance.

    Moocall HEAT allows you to use AI and it gives you live updates on the cow and bull wherever you are.

    Learn more about Moocall HEAT here.