June 2010 edition
Heat detection – a critical step!
Nathan Shannon, DPI Wodonga
Good heat detection can have a major impact on overall herd reproductive performance. InCalf research has shown that in around one-quarter of seasonal calving herds and three-quarters of year-round calving herd, heat detection errors are likely to be limiting reproductive performance.
There are two types of errors that can often occur during heat detection, you can miss a cow that is actually on heat or you can misinterpret the signs shown by a can and inseminate her at the wrong time and effectively waste the semen.
The most critical step is to accurately determine when a cow is on heat. So what are the signs of a cow on heat?
A cow is most likely to be on heat if:
- she is standing to be mounted by other cows; or
- tail paint removed or heat mount detection device is triggered.
A cow may be on heat if:
- she attempts to mount other cows;
- tail paint is rubbed but not removed;
- the heat mount detector is lost/removed;
- she is restless or bellowing;
- she has poor milk letdown;
- you see mud marks on the flanks; or
- you see mucus around the vulva.
Cows with at least two of these signs are possibly on heat but showing only weak signs. Some will be on heat. It is important that you have a process to deal with theses cows and that all members of the farm labour team understand this process.
Normally you can expect a cow to show signs of heat every 18-24 days with an average of 21 days. Cows will often have a short cycle after their first heat and are in heat again 8-12 days later. The average interval from calving to first heat in pasture fed cows in good body condition is 30-35 days, and about 10 days longer for first calving heifers.
The best heat detection programs start with careful timing, good observation and the effective use of detection aids. Being able to distinguish and interpret cow behavior and signs are critical, as are good record keeping and training for the people responsible for heat detection.
Step 1 – Review current heat detection skills – are they up to scratch? Does everyone know exactly what to look for? The period before mating is a great time to practice and train for heat detection, it will also enable you to anticipate when cows will come on heat to be inseminated.
Step 2 – Determine which aids you will use; Farmers with the best heat detection results will use a combination of observation and heat detection aids. No one method is perfect, be prepared to test a few different option to see what suits your herd.
Good paddock observation will involve checking cows in the paddock two hours after the morning milking and again two hours before the afternoon milking. For even better results cows should be checked two hours after the afternoon milking to maximise the number of cows detected.
Heat detection aids most commonly used include:
- tail paint - cheap and effective if implemented correctly and used with diligent monitoring. Different colours can be used for different groups of cattle or different cycles, i.e. change colour every three weeks of the joining period, this will help to identify cows showing only weak signs of heat. Try to tail paint a few days before you plan to check heats as tail paint is more effective if it has weathered a bit;
- heat mount detectors – more expensive but easier to read and require less maintenance once applied, generally increase heat detection rates particularly in year round calving herds or those that use large amounts of labor that varies from day to day. These can however be falsely activated by an excited cow mounting cows not on heat, particularly in a confined area;
- activity meters (pedometers) can be integrated into computerised herd information systems but are expensive. Cows on heat will be more active and data can be collected directly on to a computer which can be used in automatic drafting systems;
- telemetric heat mount detectors applied to the cows back record time and duration of mount for individuals, this provides detailed information however is expensive;
- vasectomised bulls or hormone treated steers are useful when paddock checks are not convenient. This involves attaching chin balls which mark cows across their backs once they have been mounted. The vasectomy operation should be performed at least a month before heat detection is required. Bulls still need to be rotated regularly; or
- heat synchronisation allows for intensive periods of heat detection, insemination and calving.
Each of these tools has advantages and disadvantages so it’s a matter of working out what suits your routines, budgets and goals. For more information on heat detection and the entire fertility ‘getting cows in calf’ topic, please refer to the InCalf website at www.incalf.com.au.
