Frequently Asked Questions

For more direct queries concerning your equipment please see our support portal

Why do I need a pH Bolus?

The farmBolus is used to validate and control risks when changing diets in high yielding dairy cows. When properly used, the data from the bolus can be used to optimise feeds and increase yields, thereby decreasing feed costs.

For more information see Rumen Monitoring with the farmBolus.

For trade reports on the uses of the bolus see our News page.

What’s the difference between a farmBolus and the eBolus?

The farmBolus is designed as a tool for farmers, nutritionists and veterinarians to be used for farm management. Information collected from the farmBolus is sent to a web data service hosted by eCow.

The eBolus is designed for high precision use in scientific experiments with a long life and the ability for repeated use. The eBolus allows greater flexibility in collection of data and allows the user to choose a custom data server.

How long does a bolus last?

Our pH and temperature boluses can be highly accurate for up to 150 days (5 months) in the rumen. The eBolus will shut itself off to conserve power when below 32°C. The farmBolus also includes this feature but will rarely make use of it since it spends its lifetime within the rumen of a cow (typically >35°C).

pH and temperature are checked every minute, their values are then averaged over 15 minute intervals and recorded. These intervals may be customised to fit your needs, however shorter intervals will decrease the battery life.

For a bolus in constant use the battery is unlikely to be the limiting factor. Due to the inhospitable environment within the rumen the pH sensor readings become invalid after between 90 and 150 days of continuous use. As such the farmBolus will last for roughly 90-150 days. With the ability to recalibrate the eBolus can last much longer, however the battery will eventually fail. Due to the nature of the bolus design the battery cannot be replaced.

Recent longitudinal tests have confirmed the accuracy of the eBolus pH sensor. Bolus pH sensor readings drift upwards as they age and deteriorate. When used continuously in the rumen (as is typically the case with the farmBolus), pH readings remain accurate for between 3 and 5 months. Click here to see pH readings from a trial farm over a time period of 5 months.

It has been calculated that the pH drift is +/- 0.1 pH unit per 30 days but we do not attempt to apply drift correction as this can always be done retroactively and the mechanisms behind drift are not fully understood.

Why do the pH readings drift?

pH readings tend to drift towards pH 7 and the range narrows after 3-5 months of continuous use in the reticulum. It has been calculated that the pH drift is +/- 0.1 pH unit per 30 days but we do not attempt to apply drift correction as this can always be done retroactively and the mechanisms behind drift are not fully understood.

The effect of pH drift in eCow boluses is caused by rumen fluid slowly seeping into the glass bulb pH sensor, through the protective triple junction and contaminating the reference electrode. Inside the boluses, pH is measured by the differential potential (mV) between the hydronium ions affecting the measurement electrode and the Ag/AgCl reference electrode protected by the triple junction. As rumen liquor begins to leak into the sensor and contaminate the reference the potential difference in mV between the two electrodes narrows so that the pH value appears to be rising.

We do not apply any drift correction, although with the eBolus customers have the ability to re-calibrate the device to correct the pH reading and lengthen the life of the device.

Can I extent the battery life of the bolus?

The battery life may be extended through reducing the radio activity of the bolus. This isn’t usually recommended unless re-calibration is planned, for example research customers using boluses in fistulated cows.

There are two features you can set as standard, the time window (shortest possible is 2 hours) and the radio on time (60s). This reduces operational flexibility (you only have 2 hours per day to collect data and each animal will take longer to contact) and as battery life is not usually a limiting factor it is not often advised.

For more information please see our support portal.

How much does a bolus cost?

Pricing is dependent on the number required and, if you are not in the UK, the current exchange rates. Redox sensing is an additional cost.

If you would like a quote you can follow the links for Farmer/Nutritionist (farmBolus) or Researcher (eBolus). Alternatively you can ask for a quote directly by emailing us at mail@ecow.co.uk.

How long will delivery take?

Delivery time is dependent upon the size of your order, your location and our current orders. A typical order of a box of 6 boluses within the EU should take no more than 3 weeks to be delivered.

If you would like a more up to date time frame we can provide that upon request. Please email us at mail@ecow.co.uk with your order size and the country you require them in and we will be happy to assist in your planning.

Can the bolus be used in beef cattle?

Due to a combination of excess subcutaneous fat, a less full rumen, hairier coats and the difficulty of standing near them, it is very difficult to get radio signals from boluses in beef cattle. We therefore only warranty our boluses for use in dairy cows with a maximum Body Condition Score of 2.5.

However, we’ve recently trialled a new antenna design which is providing much better connectivity and download speeds, making it possible to reliably download data from beef steers for the first time.

If you are interested in using eCow boluses in beef cattle please email us at mail@ecow.co.uk and we will advise further.

Can the bolus be used in other animals?

eCow neither warrants nor encourages the use of the eBolus and farmBolus for use in other animals. They have been designed specifically with cows in mind. However, it is theoretically possible to use the boluses in any ruminant animal with a reticulum.

The current length of the bolus means that it cannot be used in horses. It appears to get stuck at the thoracic inlet with it not being possible to advance the probe even with direct massaging of the oesophagus.

If you do plan on using a bolus in an animal other than a cow, please contact us and we will try to advise further.

Does the bolus ever come out of the cow?

Not usually. We’ve only had one case of a cow coughing up a bolus in well over 1000 administered.

Our bolus is currently 150 g, 27 mm diameter and 135 mm long, the size of a large cow pill. When ingested or placed in the rumen by fistula it moves to the reticulum. Using eCow’s patented design, the bolus stands upright in the reticulum and is designed to be heavy enough to not be passed by the cow. It remains in the reticulum until slaughter or removed by hand from a fistulated cow.

How are the boluses administered?

Boluses are swallowed by cows with the aid of a balling gun, a plastic tool often used by vets to administer medicinal boluses. As such we do not recommend boluses be inserted by anyone other than a trained animal technician with the correct training and certification.

If you do try yourself please make sure the balling gun passes past the oesophageal flap to avoid the cows lungs.

How is the pH measured?

Both the farmBolus and the eBolus use a high quality glass bulb pH sensor to continuously and accurately measure pH. This sensor is both non-toxic to the cow and resistant to abrasion from rumen sand. The end cap is designed so that particles push past the bulb rather than onto it.

The pH is calculated by measuring the voltage difference between the measurement electrode (in the rumen fluid) and the reference electrode (assumed to be pH 7). This is converted to a ADC (analogue-to-digital conversion) value and measured against pre-recorded calibration data, resulting in pH readings.

How much data does the bolus provide?

The bolus automatically takes a reading of pH and temperature every minute when it is above 32°C (in a cow). The bolus will store an average value of the pH and temperatures over a 15 minute period giving 96 readings per day.

Both boluses can store up to 2700 lines of data (28 days at 96 readings per day). Data downloads can be opened and read using the eCow Client software. Alternatively, research customers may access the raw data (.csv files) for their own specific analysis.

If necessary, the ability to measure the reduction potential (values in mV) can be included with the eBolus.

How many/which cows should be monitored?

Typically we suggest using 1 bolus per 20 to 30 cows to monitor the herd health, therefore 3 boluses for a herd of 100.

In order to get an average reading of the herd we suggest using the boluses in average early lactation cows, instead of using it to diagnose individual sickly cows.

How much data can a bolus store?
The bolus measures temperature and pH every minute and averages these readings every 15 minutes to provide 96 readings per day. It can store 2700 lines (28 days) of data before it starts overwriting the oldest information. We therefore recommend downloading from the bolus weekly but if this is not possible, no longer than 28 days apart to avoid data loss.
If you require your bolus to store more than 28 days worth of data at any one time, please contact us and we will advise further.


How often must data be collected?

The default settings allow 28 days between readings before the bolus starts overwriting data, although we recommend collecting data every week. If longer than 28 days is left between downloads it will overwrite the oldest data providing you with the most recent 28 days.

If you require your bolus to store more than 28 days worth of data at any one time, please contact us and we will advise further.

What does a data download involve?

The data is downloaded onto the handset whilst standing near the cow. The whole process of connecting and downloading data usually takes less than 10 mins and progress can be monitored on the handset. This data is then sent back to eCow over the internet and made available for viewing through the eCow Client software, as well as a preliminary pH data graph appearing immediately on the handset.

Research customers may choose to opt out of having data sent back to eCow.

Full instructions are provided upon purchase and further assistance can be provided by contacting eCow.

How do I position the antenna when downloading?

The bolus sits in the reticulum and therefore you should position the antenna behind the cows left front armpit. Pointing the antenna at the cow will work best in an ideal environment. However, we have had surprising success pointing the antenna at concrete floor next to the cow, due to signals bounce off the floor.

Please be aware radio is very non-linear, we are constantly surprised by the influence of small environmental features like metal stanchions.  The bolus rotates about every 40 seconds due to eructation/peristaltic muscular action so patience and movement of the antenna will help.

Do cows need to be restrained to download data?

Not necessarily, although it is recommended. With docile dairy cows you can often simply stand next to them and connect; however, downloads may take several minutes so the cow may need to be handled to stop it running off.


How is the data stored once I upload it?

Once uploaded the data is aggregated into one continuous rumen record for each bolus. These files are stored on our own dedicated servers and you can download and view your data using the HathorHB Client software available from the downloads section.

Data is accessible from any computer as long as it is connected to the internet and you have the required login details.

Can I use my own phone for data downloads?

Due to the complexity of our system and the requirements involved, we do not support using your own handset.

What is the format of the data? Can we deal with the data with Excel?

The data comes in .csv format which can easily be opened and brought into excel or any other analytic software of your choosing. Alternatively you can use our bespoke client software to open and view the data. The Client software can be downloaded here.

Can we replace batteries ourselves?

No, this is impossible since the bolus is completely sealed and cannot be taken apart. It was designed this way to withstand the hostile conditions within the rumen.

How do you calibrate the bolus?

Both the farmBolus and eBolus are shipped pre-calibrated, however, if used in fistulated cows, the eBolus will require recalibration between experiments.

Calibration of an eBolus can be done by the software on the handset and only requires buffers at pH 4 and 7 and a means to warm them to above 32°C. The process takes about 10 minutes. Instructions can be found in the manual provided.

If you have purchased the redox option then you repeat the process in ORP solutions, entering the mV values and paying close attention to the temperature.

Instruction manuals can be found under the user guides section.

Who designed the bolus?

Toby Mottram designed the first pH bolus when at Silsoe Research Institute. He tested the first wireless rumen pH bolus in 2003 for Pfizer and evolved the current design over 8 years at his own expense before setting up eCow.

Who typically buys the boluses?

Previously researchers were our main customer base and we have supplied products to researchers in universities around the world.

In early 2013 we expanded into commercial dairy farms in the UK and abroad with the farmBolus and data services.


Some farms insert a magnet in the rumen. Does it have any effect on the system?

We have seen no problems when our system is used in cows with magnets in Europe and the US.

Do you make temperature only boluses?
A temperature only device has such limited value we do not consider it is worth developing. Temperature only boluses are strongly affected by many factors including drinking behaviour. Our boluses do however log the temperature, and using our data viewer software you can see the temperature profile of your boluses.


For any questions not answered here, feel free to contact us and we will answer your query.