Heat detection: is your heat detection method ineffective?

Why do we need heat detection?

Heat detection is an essential component of the dairy industry. Missed or mistimed heats lead to increased calving periods and a resulting financial burden. Similarly, wasted Artificial Insemination (AI) and loss of pregnancies caused by mistiming of AI adds to this financial burden. 

There is a plethora of heat detection aids in the market, ranging from simple mount detectors like Estrotect to fully automated robotic in line systems. These heat detection aids all come with their pros and cons and in this article we aim to answer the question – is your heat detection method failing you?


Traditional methods of heat detection

Traditional methods include observing for bulling behaviours. Farmers and farm staff will observe their herd over the course of the day and look out for the tell-tale behaviours of standing heat. Unfortunately, unless the herd is observed 24/7, some heat behaviours will be missed and some cows experience ‘silent heat’ where no behaviour at all is displayed. 

These behaviours include: standing to be mounted, mounting other cows, mucous discharge and swelling or reddening of the vagina, sniffing genitalia, restlessness and many others. The only true indicator of heat is standing to be mounted, and even this behaviour can be observed for cows not in oestrous. Other behavioural indicators can happen around oestrous but cannot be used as a clear indicator for timing of AI. Furthermore, other factors such as housing conditions, nutrition, weather etc can affect these behaviours. 


What heat detection aids are available?

Given the issues with missing behaviours, silent heat, and factors affecting behaviour many dairy farms have moved to alternative methods of heat detection to replace observation or in addition to it. There is a wide range of aids available. Here are a few examples and how they are used:

Mount detectors

Kamar pressure-sensitive mount detectors, Tailhead markings, and Electronic mount detectors. The idea here is that the detector is placed on the rump of the cow. The cow will stand to be mounted, and this mounting behaviour will be detected in the different ways. Issues will this type of aid can be misplacement of the detector, false bulling behaviour and silent heat. However, this does mean behaviours may be picked up by farms that are unable to observe their cows frequently. 

Activity monitors

Pedometers like Cowlar are used to measure the activity of cows – it is well known that cows experiencing oestrous have an increase in activity. This can be great for use in busy farms without the resource to observe animals regularly. Negatives with this method are that these can also be inaccurate and may also miss silent heats as these animals to not necessarily show increased activity. Agitated cattle or cattle being moved regularly may become more active than usual, causing inaccurate readings.

Vaginal electrical resistance

The resistance of vaginal fluid is measured using a probe. The electrical resistance changes throughout the cycle and this can be a great way of tracking a single cow throughout her cycle. This technique is more hands on and difficult to incorporate into a management system, and would be difficult to implement herd wide. 

Heat expectancy charts

A simple chart based on a 21 day cycle so that farmers and farm staff can mark when oestrous has occurred or when oestrous behaviours are observed so they can time AI for the next heat. These are useful but not all cows follow a 21-day cycle – it can be different for every cow and ranges from 19-24 days. This could be used in conjunction with observation or other heat detection methods. 

Progesterone testing and monitoring

This can be incorporated into the management of a herd using pen-side testing with products such as P4Rapid to help confirm heat in suspected cows, or by using in an in line automated system like Herd Navigator. Similarly, milk samples can be tested in the laboratory to give more in depth information regarding the cows’ oestrous cycle. This method of heat detection can be used in conjunction with traditional observation of behaviours or with other heat detection aids, as a confirmation or rejection of the heat observation. It can also be used on ‘problem’ cows who are experiencing silent heats or to assist in determining what is happening when cows are showing cycles of abnormal or varying lengths. Additionally, where sexed semen is being used timing is crucial to ensure expensive semen is not wasted, therefore confirming heat prior to insemination is a must. For more information on how progesterone can be used in heat detection, visit www.P4Rapid.com


Is my heat detection method ineffective?

Farmers may use heat detection methods for all of their herd, or use observation for the majority and only monitor or test animals that they are unsure of or have not observed any oestrous like behaviours from. The issue with many heat detection aids is that they still rely on behaviour of the animal which can sometimes be unreliable and lead to missed heats or mistimed AI. These can also miss silent heats. The answer here would be to take a second test or use a progesterone test in conjunction with or instead of these, to obtain an accurate result based on the hormones being produced by the animal instead of behaviour that can be influenced by external circumstances. In most instances, it is safer and more economically sound to test when unsure of heat, as the money wasted on an AI straw and an increased calving interval can turn into a large financial burden across a farm. Similarly, inseminating an already pregnant cow can lead to spontaneous abortion, again leading to a loss. In this instance, it pays to be sure. 

Heat detection aids allow more heats to be detected, no false heats from behaviours, detection of silent heats, reduction in mistiming of AI and prevention of inseminating a pregnant cow. Next time, test your cow before AI!

References 

https://extension.psu.edu/heat-detection-and-timing-of-insemination-for-cattle#section-1